801
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Feibelman PJ. Water--From Interfaces to the Bulk. Concluding remarks. Faraday Discuss 2009; 141:467-75. [PMID: 19227370 DOI: 10.1039/b817311g] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Affiliation(s)
- Peter J Feibelman
- Sandia National Laboratories Albuquerque, Albuquerque, NM 87185-1415, USA.
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802
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Yanagisawa S, Morikawa Y. Theoretical investigation of the electronic structure of the Alq(3)/Mg interface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:064247. [PMID: 21715949 DOI: 10.1088/0953-8984/21/6/064247] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We have studied the atomic geometries and the electronic properties of the tris-(8-hydroxyquinoline) aluminum (Alq(3))/Mg interface by using density functional theoretical calculations. We have found that the chemical bond is formed between the O atoms of Alq(3) and the substrate Mg atoms, and the stability of the interface structures depends on the number of O-Mg bonds. In the up configurations, where two or three O-Mg chemical bonds are formed and the Alq(3) molecular dipoles are oriented up to the vacuum side, the work function is decreased by as much as 1.1 eV or more. The interface dipole is dominated by the orientation of the molecular dipoles of Alq(3). The interface gap state reported from experiments is ascribed to the highest occupied molecular orbital (HOMO) levels of the down configurations, which may coexist with the dominant up configurations.
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Affiliation(s)
- Susumu Yanagisawa
- The Institute of Scientific and Industrial Research (ISIR), Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka, 567-0047, Japan
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803
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Zhou JG, Williams QL. How does an external electrical field affect adsorption patterns of thiol and thiolate on the gold substrate? JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2009; 21:055008. [PMID: 21817295 DOI: 10.1088/0953-8984/21/5/055008] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
The responsive behavior of methanethiol and methylthiolate molecules on the Au(111) surface with an applied electrical potential is studied, and it is shown how the sulfur adsorption site, the S-H bond orientation and the interacting energy change with an external electric field strength. The electron charge density corresponding to an electric field minus that obtained in zero field, with zero-field optimal geometry, is calculated to explain the responsive behavior. The interacting energy for the intact methanethiol adsorption is larger than that for the dissociative one, showing that an external electric field cannot make the hydrogen dissociate from the sulfur.
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Affiliation(s)
- Jian-Ge Zhou
- Center for Molecular Structure and Interactions, Jackson State University, Jackson, MS 39217, USA. Department of Physics, Atmospheric Sciences, and Geoscience, Jackson State University, Jackson, MS 39217, USA
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804
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805
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Gordon WO, Xu Y, Mullins DR, Overbury SH. Temperature evolution of structure and bonding of formic acid and formate on fully oxidized and highly reduced CeO2(111). Phys Chem Chem Phys 2009; 11:11171-83. [DOI: 10.1039/b913310k] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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806
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Du A, Zhu Z, Sun C, Chen Y, Lu G, Smith SC. Half metallicity in a zigzag double-walled nanotube nanodot: An ab initio prediction. Chem Phys Lett 2009. [DOI: 10.1016/j.cplett.2008.12.043] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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807
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Yang S, Yoon M, Wang E, Zhang Z. Energetics and kinetics of Ti clustering on neutral and charged C60 surfaces. J Chem Phys 2008; 129:134707. [DOI: 10.1063/1.2981043] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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808
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Duan CG, Velev JP, Sabirianov RF, Zhu Z, Chu J, Jaswal SS, Tsymbal EY. Surface magnetoelectric effect in ferromagnetic metal films. PHYSICAL REVIEW LETTERS 2008; 101:137201. [PMID: 18851486 DOI: 10.1103/physrevlett.101.137201] [Citation(s) in RCA: 149] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/25/2008] [Indexed: 05/26/2023]
Abstract
A surface magnetoelectric effect is revealed by density-functional calculations that are applied to ferromagnetic Fe(001), Ni(001), and Co(0001) films in the presence of an external electric field. The effect originates from spin-dependent screening of the electric field which leads to notable changes in the surface magnetization and the surface magnetocrystalline anisotropy. These results are of considerable interest in the area of electrically controlled magnetism and magnetoelectric phenomena.
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Affiliation(s)
- Chun-Gang Duan
- Key Laboratory of Polarized Materials and Devices, Ministry of Education, East China Normal University, Shanghai 200062, China
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809
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Han S, Zhang XB, Shi SQ, Kohyama M, Tanaka H, Kuriyama N, Taoka N, Kaneko T, Xu Q. CO Adsorption on a LaNi5Hydrogen Storage Alloy Surface: A Theoretical Investigation. Chemphyschem 2008; 9:1564-9. [DOI: 10.1002/cphc.200800080] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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810
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Coquet R, Howard KL, Willock DJ. Theory and simulation in heterogeneous gold catalysis. Chem Soc Rev 2008; 37:2046-76. [PMID: 18762846 DOI: 10.1039/b707385m] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
This critical review covers the application of quantum chemistry to the burgeoning area of the heterogeneous oxidation by Au. We focus on the most established reaction, the oxidation of CO at low temperature. The review begins with an overview of the methods available comparing the treatment of the electron-electron interaction and relativistic effects. The structure of Au particles and their interaction with oxide reviews is then discussed in detail. Calculations of the adsorption and reaction of CO and O2 are then considered and results from isolated and supported Au clusters compared (155 references).
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Affiliation(s)
- Rudy Coquet
- Cardiff Catalysis Institute, School of Chemistry, Cardiff University, Main Building, Park Place, Cardiff, UK CF10 3AT
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811
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He W, Li Z, Yang J, Hou JG. Electronic structures of organic molecule encapsulated BN nanotubes under transverse electric field. J Chem Phys 2008; 129:024710. [DOI: 10.1063/1.2946708] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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812
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Giovannetti G, Khomyakov PA, Brocks G, Karpan VM, van den Brink J, Kelly PJ. Doping graphene with metal contacts. PHYSICAL REVIEW LETTERS 2008; 101:026803. [PMID: 18764212 DOI: 10.1103/physrevlett.101.026803] [Citation(s) in RCA: 785] [Impact Index Per Article: 49.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/15/2008] [Indexed: 05/25/2023]
Abstract
Making devices with graphene necessarily involves making contacts with metals. We use density functional theory to study how graphene is doped by adsorption on metal substrates and find that weak bonding on Al, Ag, Cu, Au, and Pt, while preserving its unique electronic structure, can still shift the Fermi level with respect to the conical point by approximately 0.5 eV. At equilibrium separations, the crossover from p-type to n-type doping occurs for a metal work function of approximately 5.4 eV, a value much larger than the graphene work function of 4.5 eV. The numerical results for the Fermi level shift in graphene are described very well by a simple analytical model which characterizes the metal solely in terms of its work function, greatly extending their applicability.
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Affiliation(s)
- G Giovannetti
- Instituut-Lorentz for Theoretical Physics, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherlands
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813
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Yanagisawa S, Lee K, Morikawa Y. First-principles theoretical study of Alq3∕Al interfaces: Origin of the interfacial dipole. J Chem Phys 2008; 128:244704. [DOI: 10.1063/1.2940334] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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814
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Su HY, Bao XH, Li WX. Modulating the reactivity of Ni-containing Pt(111)-skin catalysts by density functional theory calculations. J Chem Phys 2008; 128:194707. [DOI: 10.1063/1.2920174] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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815
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Lustemberg PG, Martiarena ML, Martínez AE, Busnengo HF. The reaction pathways for HSCH3 adsorption on Au(111): a density functional theory study. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2008; 24:3274-3279. [PMID: 18294013 DOI: 10.1021/la703306t] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Density functional theory was used to investigate the reaction pathways for HSCH(3) adsorption on Au(111) at low coverage. A molecular adsorbed state was found with the S atom bond on Top sites (E approximately -0.38 eV) and molecular adsorption is nonactivated. The H-SCH(3) dissociation process is energetically less favorable and becomes slightly exothermic only when surface relaxation is considered (DeltaE approximately -0.2 eV). All the reaction pathways present a sizable activation energy barrier, with the lowest being approximately 0.52 eV (0.41 eV taking into account slab relaxation). In the corresponding saddle point of the potential energy surface, the S atom of the methylthiolate molecule is placed on Top sites and the H near a Bridge site. The high barrier obtained explains the complete absence of reactive methanethiol dissociation found in recent experiments.
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Affiliation(s)
- P G Lustemberg
- Centro Atómico Bariloche, and Instituto Balseiro, Av Bustillos 9500, 8400 S. C. de Bariloche, Argentina
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816
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Zhou B, Guo W, Tang C. Chemisorption of hydrogen molecules on carbon nanotubes: charging effect from first-principles calculations. NANOTECHNOLOGY 2008; 19:075707. [PMID: 21817655 DOI: 10.1088/0957-4484/19/7/075707] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/31/2023]
Abstract
We report a systematic investigation of the charging effect on hydrogen molecule chemisorption on (3, 3), (5, 5), (5, 0), and (8, 0) carbon nanotubes by first-principles calculations. The influence of injected charge on the chemisorption energy barriers is found to be sensitive to the nanotube diameter and chirality. The calculated results also indicate that electron injection is more effective in lowering the energy barrier for armchair carbon nanotubes while hole injection is more effective for zigzag nanotubes. The origin of these interesting trends and systematics can be understood by a close examination of the underlying electronic structure and the electron transfer between the hydrogen molecules and the nanotubes.
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Affiliation(s)
- Bin Zhou
- Institute of Nano Science, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, People's Republic of China
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817
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James JN, Sholl DS. Density Functional Theory studies of dehydrogenated and zwitterionic glycine and alanine on Pd and Cu surfaces. ACTA ACUST UNITED AC 2008. [DOI: 10.1016/j.molcata.2007.06.014] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
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818
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Gokhale AA, Dumesic JA, Mavrikakis M. On the mechanism of low-temperature water gas shift reaction on copper. J Am Chem Soc 2008; 130:1402-14. [PMID: 18181624 DOI: 10.1021/ja0768237] [Citation(s) in RCA: 477] [Impact Index Per Article: 29.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Periodic, self-consistent density functional theory (DFT-GGA) calculations are used to investigate the water gas shift reaction (WGSR) mechanism on Cu(111). The thermochemistry and activation energy barriers for all the elementary steps of the commonly accepted redox mechanism, involving complete water activation to atomic oxygen, are presented. Through our calculations, we identify carboxyl, a new reactive intermediate, which plays a central role in WGSR on Cu(111). The thermochemistry and activation energy barriers of the elementary steps of a new reaction path, involving carboxyl, are studied. A detailed DFT-based microkinetic model of experimental reaction rates, accounting for both the previous and the new WGSR mechanism show that, under relevant experimental conditions, (1) the carboxyl-mediated route is the dominant path, and (2) the initial hydrogen abstraction from water is the rate-limiting step. Formate is a stable "spectator" species, formed predominantly through CO2 hydrogenation. In addition, the microkinetic model allows for predictions of (i) surface coverage of intermediates, (ii) WGSR apparent activation energy, and (iii) reaction orders with respect to CO, H2O, CO2, and H2.
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Affiliation(s)
- Amit A Gokhale
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA
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819
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Lai W, Huang W, Xie D. A first-principles study of K adsorption on Pb(111). Phys Chem Chem Phys 2008; 10:1669-74. [DOI: 10.1039/b718477h] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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820
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Nakano Y, Yanagisawa S, Hamada I, Morikawa Y. Theoretical study of vacuum level shift at the C6H6/Al(111) interface. SURF INTERFACE ANAL 2008. [DOI: 10.1002/sia.2813] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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821
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Wang Y, Hush NS, Reimers JR. Formation of Gold−Methanethiyl Self-Assembled Monolayers. J Am Chem Soc 2007; 129:14532-3. [DOI: 10.1021/ja0743442] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Yun Wang
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, NSW 2006, Australia
| | - Noel S. Hush
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, NSW 2006, Australia
| | - Jeffrey R. Reimers
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, NSW 2006, Australia
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822
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Karpan VM, Giovannetti G, Khomyakov PA, Talanana M, Starikov AA, Zwierzycki M, van den Brink J, Brocks G, Kelly PJ. Graphite and graphene as perfect spin filters. PHYSICAL REVIEW LETTERS 2007; 99:176602. [PMID: 17995355 DOI: 10.1103/physrevlett.99.176602] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/07/2007] [Indexed: 05/07/2023]
Abstract
Based upon the observations (i) that their in-plane lattice constants match almost perfectly and (ii) that their electronic structures overlap in reciprocal space for one spin direction only, we predict perfect spin filtering for interfaces between graphite and (111) fcc or (0001) hcp Ni or Co. The spin filtering is quite insensitive to roughness and disorder. The formation of a chemical bond between graphite and the open d-shell transition metals that might complicate or even prevent spin injection into a single graphene sheet can be simply prevented by dusting Ni or Co with one or a few monolayers of Cu while still preserving the ideal spin-injection property.
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Affiliation(s)
- V M Karpan
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology, University of Twente, P.O. Box 217, 7500 AE Enschede, The Netherlands
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823
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Stevanović V, Sljivancanin Z, Baldereschi A. Effect of carbon adsorption on the isomer stability of Ir4 clusters. PHYSICAL REVIEW LETTERS 2007; 99:165501. [PMID: 17995263 DOI: 10.1103/physrevlett.99.165501] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/26/2007] [Indexed: 05/25/2023]
Abstract
The atomic structure and electronic properties of gas-phase and MgO100-supported iridium tetramers are studied using density functional theory. At variance with experimental data, the most stable Ir4 isomer on MgO100 is the square one, as in the gas phase, and the metastable tetrahedral isomer is highly distorted by interactions with the substrate. In the presence of a single carbon adatom, the most stable structure of Ir4 is tetrahedral for both environments and the structural distortion of the adsorbed cluster is reduced. On MgO100, the binding energy of a C adatom to tetrahedral Ir4 is 1.6 eV larger than that to the square isomer, due to strong interactions between C-2p orbitals and a low-energy unoccupied molecular orbital of tetrahedral Ir4.
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Affiliation(s)
- Vladan Stevanović
- Institute of Theoretical Physics, Ecole Polytechnique Fédérale de Lausanne (EPFL), CH - 1015 Lausanne, Switzerland
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824
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Nagoya A, Morikawa Y. Adsorption states of methylthiolate on the Au(111) surface. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:365245. [PMID: 21694190 DOI: 10.1088/0953-8984/19/36/365245] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
We have studied the adsorption structures of methylthiolate (MeS) on the Au(111) surface using density functional theory. The most stable adsorption structure of MeS is the MeS-Au-MeS configuration, which has been proposed by Maksymovych and co-workers (2006 Phys. Rev. Lett. 97 146103), followed by the bridge configuration. The calculated work function change and vibrational mode analysis for the two configurations agree quite well with the experimental results. These results strongly support the conclusion that the MeS-Au-MeS and the bridge configurations coexist on the MeS adsorbed Au(111) surface.
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Affiliation(s)
- Akihiro Nagoya
- The Institute of Scientific and Industrial Research (ISIR), Osaka University, Mihogaoka 8-1, Ibaraki, Osaka 567-0047, Japan. CREST, Japan Science and Technology Agency (JST), 4-1-8, Honcho, Kawaguchi,Saitama 332-0012, Japan
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825
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Yoon M, Yang S, Wang E, Zhang Z. Charged fullerenes as high-capacity hydrogen storage media. NANO LETTERS 2007; 7:2578-83. [PMID: 17718530 DOI: 10.1021/nl070809a] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/16/2023]
Abstract
Using first-principles calculations within density functional theory, we explore systematically the capacity of charged carbon fullerenes Cn (20 <or= n <or= 82) as hydrogen storage media. We find that the binding strength of molecular hydrogen on either positively or negatively charged fullerenes can be dramatically enhanced to 0.18-0.32 eV, a desirable range for potential room-temperature, near ambient applications. The enhanced binding is delocalized in nature, surrounding the whole surface of a charged fullerene, and is attributed to the polarization of the hydrogen molecules by the high electric field generated near the surface of the charged fullerene. At full hydrogen coverage, these charged fullerenes can gain storage capacities of up to approximately 8.0 wt %. We also find that, contrary to intuitive expectation, fullerenes containing encapsulated metal atoms only exhibit negligible enhancement in the hydrogen binding strength, because the charge donated by the metal atoms is primarily confined inside the fullerene cages. These predictions may prove to be instrumental in searching for a new class of high-capacity hydrogen storage media.
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Affiliation(s)
- Mina Yoon
- Materials Science and Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
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826
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Wang XG, Fisher GB. Phase diagram of molecular oxygen adsorption on the (111) platinum surface. PHYSICAL REVIEW LETTERS 2007; 99:066101. [PMID: 17930841 DOI: 10.1103/physrevlett.99.066101] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/20/2007] [Indexed: 05/25/2023]
Abstract
Molecular oxygen adsorption on the Pt(111) surface is studied based on ab initio computations and thermodynamics. An O2 adsorption phase diagram is determined. There are two possible chemisorbed molecular states: one at a bridge site and another one at an fcc hollow site. While some population in the bridge sites persists at all coverages, the states coexist through the intermediate coverage phases. The relative coverage of the two species on the surface is determined by the competition between the Pt lattice distortion energy (that results from O2 adsorption) and the O2 repulsion energy. Our results give a reasonable explanation for the seemingly contradictory findings in previous experimental and theoretical work.
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Affiliation(s)
- Xiao-Gang Wang
- Delphi Research Labs, Shelby Township, Michigan 48315, USA
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827
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Montoya A, Schlunke A, Haynes BS. Reaction of hydrogen with Ag(111): binding states, minimum energy paths, and kinetics. J Phys Chem B 2007; 110:17145-54. [PMID: 16928010 DOI: 10.1021/jp062725g] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The interaction of atomic and molecular hydrogen with the Ag(111) surface is studied using periodic density functional total-energy calculations. This paper focuses on the site preference for adsorption, ordered structures, and energy barriers for H diffusion and H recombination. Chemisorbed H atoms are unstable with respect to the H(2) molecule in all adsorption sites below monolayer coverage. The three-hollow sites are energetically the most favorable for H chemisorption. The binding energy of H to the surface decreases slightly up to one monolayer, suggesting a small repulsive H-H interaction on nonadjacent sites. Subsurface and vacancy sites are energetically less favorable for H adsorption than on-top sites. Recombination of chemisorbed H atoms leads to the formation of gas-phase H(2) with no molecular chemisorbed state. Recombination is an exothermic process and occurs on the bridge site with a pronounced energy barrier. This energy barrier is significantly higher than that inferred from experimental temperature-programmed desorption (TPD) studies. However, there is significant permeability of H atoms through the recombination energy barrier at low temperatures, thus increasing the rate constant for H(2) desorption due to quantum tunneling effects, and improving the agreement between experiment and theory.
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Affiliation(s)
- Alejandro Montoya
- School of Chemical and Biomolecular Engineering, The University of Sydney, Sydney, NSW 2006, Australia.
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828
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Mitsui T, Fomin E, Ogletree D, Salmeron M, Nilekar A, Mavrikakis M. Manipulation and Patterning of the Surface Hydrogen Concentration on Pd(111) by Electric Fields. Angew Chem Int Ed Engl 2007. [DOI: 10.1002/ange.200604498] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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829
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Yang MM, Bao XH, Li WX. Density functional theory study of CHx (x=1–3) adsorption on clean and CO precovered Rh(111) surfaces. J Chem Phys 2007; 127:024705. [PMID: 17640143 DOI: 10.1063/1.2751155] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
CH(x) (x=1-3) adsorptions on clean and CO precovered Rh(111) surfaces were studied by density functional theory calculations. It is found that CH(x) (x=1-3) radicals prefer threefold hollow sites on Rh(111) surfaces, and the bond strength between CH(x) and Rh(111) follows the order of CH(3)<CH(2)<CH. A slight attraction between adsorbed CH(x) and CH(x), CH(x) and CO, CO and CO radicals/molecules at coverage of 1/9-1/4 ML is found, and considerable repulsion is built up at coverage higher than 1/4 ML. It is found that CH(x) adsorption results in the reduction of work function due to charge transfer from the adsorbates to the substrate. For CH(3) adsorption, charge accumulation between the substrate and carbon atom is identified, which results in C-H stretch mode softening. For CO precovered surfaces, the mode softening is prevented due to the weakened interaction between CH(x) and substrates from repulsive interaction between adsorbates. Conversely, the overall charge transfer from the CH(x) (x=1-3) to the substrate enhances the charge back donation from the substrate to the empty antibonding states of adsorbed carbon monoxide, which results in the softness of the C-O stretch, respectively. The C 1s surface core-level shifts for CH(x) with and without the presence of CO were calculated, and a negative shift with respect to the carbon in atop CO on Rh(111) is found, and the negative shift follows the order of CO<CH(3)<CH(2)<CH. The results are analyzed in details by difference of charge density and projected density of states.
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Affiliation(s)
- Ming-Mei Yang
- State Key Laboratory Of Catalysis, Dalian Institute of Chemical Physics, Chinese Academy of Sciences, 457 Zhongshan Road, Dalian 116023, China
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830
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Rusina GG, Eremeev SV, Borisova SD, Sklyadneva IY, Echenique PM, Chulkov EV. Phonons in the ordered c(2 × 2) phases of Na and Li on Al(001). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2007; 19:266005. [PMID: 21694074 DOI: 10.1088/0953-8984/19/26/266005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
The vibrational properties of the Al(001)-c(2 × 2)-Na (Li) ordered phases formed by alkali atoms (Na and Li) on the Al(001) surface at low and room temperatures are presented. The equilibrium structural characteristics, phonon dispersions and polarization of vibrational modes as well as the local density of phonon states are calculated using the embedded-atom method. The obtained structural parameters are in close agreement with experimental data.
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Affiliation(s)
- G G Rusina
- Institute of Strength Physics and Materials Science SB RAS, 634021, Tomsk, Russia
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831
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Mitsui T, Fomin E, Ogletree DF, Salmeron M, Nilekar AU, Mavrikakis M. Manipulation and patterning of the surface hydrogen concentration on Pd(111) by electric fields. Angew Chem Int Ed Engl 2007; 46:5757-61. [PMID: 17585396 DOI: 10.1002/anie.200604498] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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832
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Knudsen J, Nilekar AU, Vang RT, Schnadt J, Kunkes EL, Dumesic JA, Mavrikakis M, Besenbacher F. A Cu/Pt Near-Surface Alloy for Water−Gas Shift Catalysis. J Am Chem Soc 2007; 129:6485-90. [PMID: 17469820 DOI: 10.1021/ja0700855] [Citation(s) in RCA: 209] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The primary route to hydrogen production from fossil fuels involves the water-gas shift (WGS) reaction, and an improvement in the efficiency of WGS catalysts could therefore lead to a major leap forward in the realization of hydrogen economy. On the basis of a combination of high-resolution scanning tunneling microscopy, X-ray photoelectron spectroscopy, and density functional theory (DFT) calculations, we suggest the existence of a new thermodynamically stable Cu/Pt near-surface alloy (NSA). Temperature-programmed desorption and DFT reveal that this Cu/Pt NSA binds CO significantly more weakly than does Pt alone, thereby implying a considerable reduction in the potential for CO poisoning of the Cu/Pt NSA surface as compared to that of pure Pt. In addition, DFT calculations show that this Cu/Pt NSA is able to activate H2O easily, which is the rate-determining step for the WGS on several metal surfaces, and, at the same time, to bind the products of that reaction and formate intermediates rather weakly, thus avoiding possible poisoning of the catalyst surface. The Cu/Pt NSA is thus a promising candidate for an improved WGS catalyst.
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Affiliation(s)
- Jan Knudsen
- Interdisciplinary Nanoscience Center (iNANO) and Department of Physics and Astronomy, University of Aarhus, DK-8000 Aarhus C, Denmark
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833
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Maul R, Preuss M, Ortmann F, Hannewald K, Bechstedt F. Electronic excitations of glycine, alanine, and cysteine conformers from first-principles calculations. J Phys Chem A 2007; 111:4370-7. [PMID: 17461555 DOI: 10.1021/jp068294j] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The electronic and optical properties are studied for three conformers of amino acid molecules using gradient-corrected (spin-) density functional theory within a projector-augmented wave scheme and the supercell method. We investigate single-particle excitations such as ionization energies and electron affinities as well as pair excitations. By comparing eigenvalues resulting from several local and nonlocal energy functionals, the influence of treatment of exchange and correlation is demonstrated. The excitations are described within the Delta-self-consistent field method with an occupation number constraint to obtain excitation energies and Stokes shifts. The results are used to also discuss the optical absorption properties. In contrast to the lowest single- and two-particle excitation energies, remarkable changes are found in absorption spectra in dependence on the conformation of the molecule geometry.
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Affiliation(s)
- R Maul
- Institut für Festkörpertheorie und-optik, Friedrich-Schiller-Universität Jena, Max-Wien-Platz 1, 07743 Jena, Germany
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834
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Chen G, Kawazoe Y. Structural and electronic properties of Al12X+ (X=C, Si, Ge, Sn, and Pb) clusters. J Chem Phys 2007; 126:014703. [PMID: 17212507 DOI: 10.1063/1.2429063] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using the first-principles method with the generalized gradient approximation, the authors have studied the structural and electronic properties of Al(12)X(+) (X=C, Si, Ge, Sn, and Pb) clusters in detail. The ground state of Al(12)C(+) is a low symmetry C(s) structure instead of an icosahedron. However, the Si, Ge, Sn, and Pb atom doped cationic clusters favor icosahedral structures. The ground states for Al(12)Si(+) and Al(12)Ge(+) are icosahedra, while the C(5nu) structures optimized from an icosahedron with a vertex capped by a tetravalent atom have the highest binding energy for Al(12)Sn(+) and Al(12)Pb(+) clusters. The I(h) structure and the C(5nu) structure are almost degenerate for Al(12)Ge(+), whose binding energy difference is only 0.03 eV. The electronic properties are altered much by removing an electron from the neutral cluster. The binding strength of a valence electron is enhanced, while the binding energy of the cluster is reduced much. Due to the open electronic shell, the band gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital are approximately 0.3 eV for the studied cationic clusters.
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Affiliation(s)
- G Chen
- Institute for Materials Research, Tohoku University, Aoba-ku, Sendai 980-8577, Japan
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835
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Abstract
The adsorptions of K and Cs on Pd(111) were studied by the density functional calculations within the generalized gradient approximation. The site preference, bonding character, work function, and electron structure of the system were analyzed. For K and Cs adsorption, the hcp hollow site was found to be preferred for all the coverages investigated. The calculated adsorption geometries for (2 x 2) and (square root 3 x square root 3)R30 degrees phases are both in reasonable agreement with the observed results. The decrease of the work function upon the adsorption of K and Cs can be attributed to a dipole moment associated with the polarized adsorbate atom, which is characterized by depletion of the electron charge in the alkali metal layer and a charge accumulation in the interface region. Our results indicate that the bonding of alkali metal with the Pd(111) surface has a mixed ionic and metallic bond character at low coverage and a metallic bond of covalent character at high coverage.
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Affiliation(s)
- Wenzhen Lai
- Institute of Theoretical and Computational Chemistry, Key Laboratory of Mesoscopic Chemistry, School of Chemistry and Chemical Engineering, Nanjing University, Nanjing 210093, China
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836
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N'Diaye AT, Bleikamp S, Feibelman PJ, Michely T. Two-dimensional Ir cluster lattice on a graphene moiré on Ir(111). PHYSICAL REVIEW LETTERS 2006; 97:215501. [PMID: 17155746 DOI: 10.1103/physrevlett.97.215501] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2006] [Indexed: 05/12/2023]
Abstract
Lattices of Ir clusters have been grown by vapor phase deposition on graphene moirés on Ir(111). The clusters are highly ordered, and spatially and thermally stable below 500 K. Their narrow size distribution is tunable from 4 to about 130 atoms. A model for cluster binding to the graphene is presented based on scanning tunneling microscopy and density functional theory. The proposed binding mechanism suggests that similar cluster lattices might be grown of materials other than Ir.
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Affiliation(s)
- Alpha T N'Diaye
- I. Physikalisches Institut, RWTH Aachen, 52056 Aachen, Germany.
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837
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Nilekar AU, Greeley J, Mavrikakis M. A Simple Rule of Thumb for Diffusion on Transition-Metal Surfaces. Angew Chem Int Ed Engl 2006. [DOI: 10.1002/ange.200602223] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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838
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Nilekar AU, Greeley J, Mavrikakis M. A Simple Rule of Thumb for Diffusion on Transition-Metal Surfaces. Angew Chem Int Ed Engl 2006; 45:7046-9. [PMID: 17009349 DOI: 10.1002/anie.200602223] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Anand Udaykumar Nilekar
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, Madison, WI 53706, USA
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839
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Rusu PC, Brocks G. Surface Dipoles and Work Functions of Alkylthiolates and Fluorinated Alkylthiolates on Au(111). J Phys Chem B 2006; 110:22628-34. [PMID: 17092010 DOI: 10.1021/jp0642847] [Citation(s) in RCA: 146] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
We study the dipole formation at the surface formed by -CH(3) and -CF(3) terminated short-chain alkylthiolate monolayers on Au(111). In particular, we monitor the change in work function upon chemisorption using density functional theory calculations. We separate the surface dipole into two contributions, resulting from the gold-adsorbate interaction and the intrinsic dipole of the adsorbate layer, respectively. The two contributions turn out to be approximately additive. Adsorbate dipoles are defined by calculating dipole densities of free-standing molecular monolayers. The gold-adsorbate interaction is, to a good degree, determined by the Au-S bond only. This bond is nearly apolar and its contribution to the surface dipole is relatively small. The surface dipole of the self-assembled monolayer is then dominated by the intrinsic dipole of the thiolate molecules. Alkylthiolates increase the work function of Au(111), whereas fluorinated alkylthiolates decrease it.
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Affiliation(s)
- Paul C Rusu
- Faculty of Science and Technology and MESA+ Institute for Nanotechnology,University of Twente, P. O. Box 217, 7500 AE Enschede, The Netherlands
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840
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Saalfrank P. Quantum Dynamical Approach to Ultrafast Molecular Desorption from Surfaces. Chem Rev 2006; 106:4116-59. [PMID: 17031982 DOI: 10.1021/cr0501691] [Citation(s) in RCA: 130] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Peter Saalfrank
- Theoretische Chemie, Institut für Chemie, Universität Potsdam, Karl-Liebknecht-Strasse 24-25, D-14476 Potsdam-Golm, Germany
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841
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Rankin RB, Sholl DS. Structures of dense glycine and alanine adlayers on chiral Cu(3,1,17) surfaces. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2006; 22:8096-103. [PMID: 16952247 DOI: 10.1021/la0613272] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Density Functional Theory calculations have been used to predict the structures of dense glycine and alanine adlayers on Cu(3,1,17)(S). Facets of this chiral Cu surface result from adsorbate-induced surface reconstruction when glycine or alanine are adsorbed and annealed on Cu(100). We have calculated the surface energy changes associated with this surface reconstruction. Our results allow the enantiospecificity of this reconstruction following adsorption of enantiopure or racemic alanine on Cu(100) to be discussed. The overall stability of glycine and alanine adlayers on Cu(3,1,17)(S) arises from an interplay between the formation of chemical bonds with the Cu surface, deformations in the adsorbed molecules during adsorption, and intermolecular hydrogen bonds within the adlayer; none of these factors individually dominates.
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Affiliation(s)
- Rees B Rankin
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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842
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Hellman A, Baerends EJ, Biczysko M, Bligaard T, Christensen CH, Clary DC, Dahl S, van Harrevelt R, Honkala K, Jonsson H, Kroes GJ, Luppi M, Manthe U, Nørskov JK, Olsen RA, Rossmeisl J, Skúlason E, Tautermann CS, Varandas AJC, Vincent JK. Predicting Catalysis: Understanding Ammonia Synthesis from First-Principles Calculations. J Phys Chem B 2006; 110:17719-35. [PMID: 16956255 DOI: 10.1021/jp056982h] [Citation(s) in RCA: 167] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Here, we give a full account of a large collaborative effort toward an atomic-scale understanding of modern industrial ammonia production over ruthenium catalysts. We show that overall rates of ammonia production can be determined by applying various levels of theory (including transition state theory with or without tunneling corrections, and quantum dynamics) to a range of relevant elementary reaction steps, such as N(2) dissociation, H(2) dissociation, and hydrogenation of the intermediate reactants. A complete kinetic model based on the most relevant elementary steps can be established for any given point along an industrial reactor, and the kinetic results can be integrated over the catalyst bed to determine the industrial reactor yield. We find that, given the present uncertainties, the rate of ammonia production is well-determined directly from our atomic-scale calculations. Furthermore, our studies provide new insight into several related fields, for instance, gas-phase and electrochemical ammonia synthesis. The success of predicting the outcome of a catalytic reaction from first-principles calculations supports our point of view that, in the future, theory will be a fully integrated tool in the search for the next generation of catalysts.
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Affiliation(s)
- A Hellman
- Haldor Topsøe A/S, Nymøllevej 55, DK-2800 Lyngby, Denmark.
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843
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Rempel JY, Trout BL, Bawendi MG, Jensen KF. Density Functional Theory Study of Ligand Binding on CdSe (0001), (0001̄), and (112̄0) Single Crystal Relaxed and Reconstructed Surfaces: Implications for Nanocrystalline Growth. J Phys Chem B 2006; 110:18007-16. [PMID: 16956292 DOI: 10.1021/jp064051f] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
To gain a better understanding of the influence of ligand-surface interactions on nanocrystalline growth, periodic density functional theory calculations were employed in the study of the binding of organic ligands on the relaxed nonpolar (1120) and polar Se terminated (0001) surfaces and the relaxed and vacancy and adatom reconstructed Cd terminated (0001) surface. We examined chemisorption properties of phosphine, amine, phosphine oxide, carboxylic acid, and phosphinic acid model ligands, including preferred binding sites and geometries, vibrational frequencies, and binding energetics, and compared findings to intrinsic growth via addition of CdSe molecules or Cd and Se atoms. Our results indicate that binding of the ligands is preferred in the electron-poor 1-fold sites on all surfaces, with secondary coordination of the acidic ligands through the hydroxyl hydrogen to the electron-rich surface sites. In general ligand adsorption directly obstructs binding sites for growth species on the (1120) surface and only indirectly on the two polar surfaces. The order of binding affinities on the (1120) and (0001) surfaces is PH(3) < OPH(3) approximately HCOOH < NH(3) < OPH(2)OH and that on the (0001) surface is OPH(3) approximately HCOOH < OPH(2)OH < NH(3) < PH(3). Our findings corroborate the experimental observation that incorporation of the nonbulky phosphinic acid-type ligands with high affinity and high selectivity for both the (1120) and (0001) surfaces strongly enhances unidirectional growth on the (0001) surface, while incorporation of either bulky ligands or ligands with moderate affinity does not. Higher affinity of all traditionally used ligands for the (1120) surface compared to the (0001) surface also suggests that new ligands should be engineered to achieve the synthesis of novel shapes that require preferential growth on the (1120) surface.
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Affiliation(s)
- Jane Y Rempel
- Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA
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844
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845
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846
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Wang JG, Hammer B. Density functional theory study of water dissociation in a double water bilayer with or without coadsorption of CO on Pt(111). J Chem Phys 2006; 124:184704. [PMID: 16709128 DOI: 10.1063/1.2192514] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Using density functional theory, we investigate the structure of the double water bilayer with or without coadsorption of CO on Pt(111). The double water bilayer consists of two bilayers. Each bilayer is buckled with every second water molecule being closer to the surface than every other water molecule. CO is found to adsorb most strongly when substituting in the first bilayer, the water molecule closest to the surface. Dissociation of H2O in the water bilayer (with or without CO) is further considered. A great number of pathways for the dissociation are studied. These include homolytic pathways where both dissociation products end up adsorbed on the Pt surface and heterolytic pathways where only the OH is adsorbed, while a proton is transferred to the water adlayers. We find that the heterolytic dissociation pathways are energetically more favorable than the homolytic ones, yet they are all rather endothermic. The most favorable pathways found have reaction energies of 0.60 and 0.52 eV without and with CO present. The corresponding activation energies are 0.99 and 0.53 eV, respectively.
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Affiliation(s)
- J G Wang
- iNANO, University of Aarhus, DK-8000 Aarhus C, Denmark
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847
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Bilić A, Reimers JR, Hush NS, Hoft RC, Ford MJ. Adsorption of Benzene on Copper, Silver, and Gold Surfaces. J Chem Theory Comput 2006; 2:1093-105. [DOI: 10.1021/ct050237r] [Citation(s) in RCA: 132] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Ante Bilić
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, New South Wales 2006, Australia, and Institute for Nanoscale Technology, University of Technology, Sydney, P.O. Box 123, Broadway, New South Wales 2007, Australia
| | - Jeffrey R. Reimers
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, New South Wales 2006, Australia, and Institute for Nanoscale Technology, University of Technology, Sydney, P.O. Box 123, Broadway, New South Wales 2007, Australia
| | - Noel S. Hush
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, New South Wales 2006, Australia, and Institute for Nanoscale Technology, University of Technology, Sydney, P.O. Box 123, Broadway, New South Wales 2007, Australia
| | - Rainer C. Hoft
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, New South Wales 2006, Australia, and Institute for Nanoscale Technology, University of Technology, Sydney, P.O. Box 123, Broadway, New South Wales 2007, Australia
| | - Michael J. Ford
- School of Chemistry and School of Molecular and Microbial Biosciences, The University of Sydney, New South Wales 2006, Australia, and Institute for Nanoscale Technology, University of Technology, Sydney, P.O. Box 123, Broadway, New South Wales 2007, Australia
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848
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Kiejna A, Pabisiak T, Gao SW. The energetics and structure of rutile TiO(2)(110). JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2006; 18:4207-4217. [PMID: 21690775 DOI: 10.1088/0953-8984/18/17/009] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Density functional theory and a pseudopotential plane wave method are applied to study electronic and structural properties of the defect-free TiO(2)(110) surface. The variations of the surface energy, work function, and atomic displacements are examined for partially and fully relaxed slabs modelling the rutile (110) surface, and consisting of up to 33 atomic layers. Relatively small relaxations of atomic positions in the outermost layers have a strong influence on the calculated surface energies and work functions. The effect of nonequivalence of the odd-even layer terminations is explored. A simple method is proposed which allows one to estimate accurate surface energies for relaxed systems from calculations for partially relaxed slabs.
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Affiliation(s)
- A Kiejna
- Institute of Experimental Physics, University of Wrocław, Plac M Borna 9, PL-50-204 Wrocław, Poland
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849
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Leung K, Rempe SB, Schultz PA, Sproviero EM, Batista VS, Chandross ME, Medforth CJ. Density Functional Theory and DFT+U Study of Transition Metal Porphines Adsorbed on Au(111) Surfaces and Effects of Applied Electric Fields. J Am Chem Soc 2006; 128:3659-68. [PMID: 16536538 DOI: 10.1021/ja056630o] [Citation(s) in RCA: 91] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We apply density functional theory (DFT) and the DFT+U technique to study the adsorption of transition metal porphine molecules on atomistically flat Au(111) surfaces. DFT calculations using the Perdew-Burke-Ernzerhof exchange correlation functional correctly predict the palladium porphine (PdP) low-spin ground state. PdP is found to adsorb preferentially on gold in a flat geometry, not in an edgewise geometry, in qualitative agreement with experiments on substituted porphyrins. It exhibits no covalent bonding to Au(111), and the binding energy is a small fraction of an electronvolt. The DFT+U technique, parametrized to B3LYP-predicted spin state ordering of the Mn d-electrons, is found to be crucial for reproducing the correct magnetic moment and geometry of the isolated manganese porphine (MnP) molecule. Adsorption of Mn(II)P on Au(111) substantially alters the Mn ion spin state. Its interaction with the gold substrate is stronger and more site-specific than that of PdP. The binding can be partially reversed by applying an electric potential, which leads to significant changes in the electronic and magnetic properties of adsorbed MnP and approximately 0.1 A changes in the Mn-nitrogen distances within the porphine macrocycle. We conjecture that this DFT+U approach may be a useful general method for modeling first-row transition metal ion complexes in a condensed-matter setting.
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Affiliation(s)
- Kevin Leung
- Sandia National Laboratories, MS 1415, 1110, 0310, 1411, & 1349, Albuquerque, New Mexico 87185, USA.
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850
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Rankin RB, Sholl DS. First-principles studies of chiral step reconstructions of Cu(100) by adsorbed glycine and alanine. J Chem Phys 2006; 124:74703. [PMID: 16497066 DOI: 10.1063/1.2168440] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Adsorption of amino acids on Cu(100) is known experimentally to induce surface reconstructions featuring intrinsically chiral Cu(3,1,17) facets, but no information about the geometry of the molecules on these chiral facets is available. We present density-functional theory calculations for the structure of glycine and alanine at moderate coverages on Cu(3,1,17). As might be expected, molecules prefer to bind at the step edges on this surface rather than on the surface's (100)-oriented terraces. The adsorption of enantiopure alanine on Cu(3,1,17) is predicted to be weakly enantiospecific, with S-alanine being more stable on Cu(3,1,17)(S) than R-alanine. By comparing the surface energies of Cu(100) and Cu(3,1,17) in the presence of adsorbed glycine or alanine, our calculations provide insight into the driving force for chiral reconstructions of Cu(100) by amino acids.
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Affiliation(s)
- Rees B Rankin
- Department of Chemical Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA
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