251
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A new global reaction route map on the potential energy surface of H2CO with unrestricted level. Chem Phys Lett 2008. [DOI: 10.1016/j.cplett.2008.06.003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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252
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Luo Y, Maeda S, Ohno K. DFT Study on Isomerization and Decomposition of Cuprous Dialkyldithiophosphate and Its Reaction with Alkylperoxy Radical. J Phys Chem A 2008; 112:5720-6. [DOI: 10.1021/jp801571b] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Yi Luo
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Satoshi Maeda
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Koichi Ohno
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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253
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Maeda S, Watanabe Y, Ohno K. Finding important anharmonic terms in the sixth-order potential energy function by the scaled hypersphere search method: An application to vibrational analyses of molecules and clusters. J Chem Phys 2008; 128:144111. [DOI: 10.1063/1.2884348] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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254
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Maeda S, Ohno K. Microsolvation of Hydrogen Sulfide: Exploration of H2S·(H2O)n and SH-·H3O+·(H2O)n-1 (n = 5−7) Cluster Structures on Ab Initio Potential Energy Surfaces by the Scaled Hypersphere Search Method. J Phys Chem A 2008; 112:2962-8. [DOI: 10.1021/jp710494n] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Satoshi Maeda
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Koichi Ohno
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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255
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Maeda S, Ohno K. Automated Exploration of Adsorption Structures of an Organic Molecule on RuH2−BINAP by the ONIOM Method and the Scaled Hypersphere Search Method. J Phys Chem A 2007; 111:13168-71. [DOI: 10.1021/jp709874f] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Satoshi Maeda
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
| | - Koichi Ohno
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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256
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Watanabe Y, Maeda S, Ohno K. Global reaction route mapping on potential energy surfaces of C2H7+ and C3H9+. Chem Phys Lett 2007. [DOI: 10.1016/j.cplett.2007.09.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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257
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Luo Y, Maeda S, Ohno K. Quantum Chemistry Study of H+(H2O)8: A Global Search for Its Isomers by the Scaled Hypersphere Search Method, and Its Thermal Behavior. J Phys Chem A 2007; 111:10732-7. [PMID: 17887737 DOI: 10.1021/jp074819b] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Abstract
The structures of the protonated water cluster H+(H2O)8 have been globally explored by the scaled hypersphere search method. On the Hartree-Fock potential energy surface 174 isomers were found, among which 168 were computed to be minima at the B3LYP/6-31+G** level, and their energies were further refined at the level of MP2/6-311++G(3df,2p). The global minimum on the potential energy surface computed at the B3LYP/6-31+G** level shows a cagelike structure with the "Eigen" motif, while the lowest-free-energy isomer has a five-membered-ring structure at 170 K and a chain form at 273 K. The present results are well in line with previous experimental findings. In addition, the ADMP (atom-centered density matrix propagation) simulation indicates that the extra proton in the lowest-free-energy isomer (170 K), which has a five-membered ring and the "Zundel" feature, is often in an asymmetrical hydrogen bond.
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Affiliation(s)
- Yi Luo
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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258
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Yang X, Maeda S, Ohno K. Insight into Global Reaction Mechanism of [C2, H4, O] System from ab Initio Calculations by the Scaled Hypersphere Search Method. J Phys Chem A 2007; 111:5099-110. [PMID: 17506536 DOI: 10.1021/jp071238d] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
A detailed computational study is performed on the singlet potential energy surface (PES) for possible isomerization and dissociation reactions of CH(3)CHO at the DFT (B3LYP/6-311++G(d,p)) and CCSD(T)/cc-pVTZ//B3LYP/6-311++G(d,p) levels. The pathways around the equilibrium structures can be discovered by the scaled hypersphere search (SHS) method, which enables us to make a global analysis of the PES for a given chemical composition. Fourteen isomers inclusive of 11 single-molecules and three "non-stabilized" oxygen-based ylides, 5 energetically favored complexes, and 79 interconversion transition states have been found on the singlet PES. Four lowest lying isomers with thermodynamic stability are also kinetically stable with respect to metastable intermediates. It was revealed that vinyl alcohols, which could be generated by the tautomerization of acetaldehyde, could undergo dissociation to form acetylene and water. In addition, recombination channels between some fragments, such as H(2)CO + (1)CH(2) and (1)CHOH + (1)CH(2), are energetically accessible via collision complex or oxygen-based ylides. Most of available unimolecular decompositions are found to be responsible for favorable hydrogen abstraction processes.
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Affiliation(s)
- Xia Yang
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Sendai 980-8578, Japan
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259
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Maeda S, Ohno K. Structures of Water Octamers (H2O)8: Exploration on Ab Initio Potential Energy Surfaces by the Scaled Hypersphere Search Method. J Phys Chem A 2007; 111:4527-34. [PMID: 17461560 DOI: 10.1021/jp070606a] [Citation(s) in RCA: 111] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
Abstract
The potential energy surface (PES) of water octamers has been explored by the scaled hypersphere search method. Among 164 minima on the PES (based on MP2/6-311++G(3df,2p)//B3LYP/6-311+G(d,p) calculations), the cubic structure with D2d symmetry has been confirmed to be the global minimum. In a thermodynamic simulation using these 164 structures, the cubic structure with S4 symmetry has the highest population at low temperature, though double rings can become dominant as temperature going up, in good accord with a recent Monte Carlo simulation using an empirical potential. A transition temperature from cubic to noncubic has significantly been underestimated when potential energy data of B3LYP/6-311+G(d,p) calculations are employed in the simulation. This serious discrepancy between the MP2 and the B3LYP results suggests an importance of dispersion interactions for discussions on thermodynamics of water octamers.
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Affiliation(s)
- Satoshi Maeda
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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260
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Santiso EE, George AM, Gubbins KE, Buongiorno Nardelli M. Effect of confinement by porous carbons on the unimolecular decomposition of formaldehyde. J Chem Phys 2006; 125:084711. [PMID: 16965043 DOI: 10.1063/1.2220566] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
As part of an effort to understand the effect of confinement by porous carbons on chemical reactions, we have carried out density functional theory calculations on the unimolecular decomposition of formaldehyde within graphitic carbons. Our results show that the interactions with the carbon walls result in a lowering of the reaction barrier. For larger pores, there is also a shift of the equilibrium towards the formation of carbon monoxide and hydrogen at low temperatures. This trend is reversed for small pore sizes.
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Affiliation(s)
- Erik E Santiso
- Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, NC 27695, USA.
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261
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Ohno K, Maeda S. Global Reaction Route Mapping on Potential Energy Surfaces of Formaldehyde, Formic Acid, and Their Metal-Substituted Analogues. J Phys Chem A 2006; 110:8933-41. [PMID: 16836457 DOI: 10.1021/jp061149l] [Citation(s) in RCA: 248] [Impact Index Per Article: 13.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Global reaction route mapping of equilibrium structures, transition structures, and their connections on potential energy surface (PES) has been done for MCHO (M = H, Li, Na, Al, Cu) and HCO2M (M = H, Li). A one-after-another technique based on the scaled hypersphere search method has been successfully applied to exploring unknown chemical structures, transition structures, and reaction pathways for organometallic systems. Upon metal substitution, considerable changes of stable structures, reaction pathways, and relative heights of transition structures have been discovered, though some features are similar among the analogues. Al and Cu atoms were found to behave as very strong scissors to cut the CO double bond in MCHO. Energy profiles of the CO insertion into Li-H and Li-CH3 bonds were found to be very similar, especially around the structures where the Li atom is not directly connected with the methyl group, which indicates little effects of alkyl substitution on the reaction route topology.
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Affiliation(s)
- Koichi Ohno
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Sendai 980-8578, Japan.
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262
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Maeda S, Ohno K. Conversion pathways between a fullerene and a ring among C20 clusters by a sphere contracting walk method: Remarkable difference in local potential energy landscapes around the fullerene and the ring. J Chem Phys 2006; 124:174306. [PMID: 16689570 DOI: 10.1063/1.2192784] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Conversion pathways from a fullerene to a ring and vice versa among C(20) clusters have been explored. A new technique has been developed for discovering multistep reaction pathways, which can be searched by finding constrained energy minima on spheres whose surfaces are contracting from the starting point to the terminal. Local landscapes that appeared on the pathways were found to be considerably different around the fullerene and the ring, from which one can make a new interpretation for no generation of the C(20) fullerene in laser vaporization of graphite.
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Affiliation(s)
- Satoshi Maeda
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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263
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Ohno K, Maeda S. D–L Conversion Pathways between Optical Isomers of Alanine: Applications of the Scaled Hypersphere Search Method to Explore Unknown Reaction Routes in a Chiral System. CHEM LETT 2006. [DOI: 10.1246/cl.2006.492] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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264
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Yang X, Maeda S, Ohno K. Global analysis of reaction pathways on the potential energy surface of cyanoacetylene by the scaled hypersphere search method. Chem Phys Lett 2006. [DOI: 10.1016/j.cplett.2005.10.132] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
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265
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A scaled hypersphere interpolation technique for efficient construction of multidimensional potential energy surfaces. Chem Phys Lett 2005. [DOI: 10.1016/j.cplett.2005.08.063] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
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266
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Yang X, Maeda S, Ohno K. Global Investigation on the Potential Energy Surface of CH3CN: Application of the Scaled Hypersphere Search Method. J Phys Chem A 2005; 109:7319-28. [PMID: 16834097 DOI: 10.1021/jp052067k] [Citation(s) in RCA: 53] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
An extensive quantum chemical study of the potential energy surface (PES) for all possible isomerization and dissociation reactions of CH3CN is reported at the DFT (B3LYP/6-311++G(d,p)) and CCSD(T)/ cc-pVTZ//B3LYP/6-311++G(d,p) levels of theory. The pathways around the equilibrium structures can be discovered by the scaled hypersphere search (SHS) method, which enables us to make a global analysis of the potential energy surface for a given chemical composition in combination with a downhill-walk algorithm. Seventeen equilibrium structures and 59 interconversion transition states have been found on the singlet PES. The four lowest lying isomers with thermodynamic stability are also kinetically stable with the lowest conversion barriers of 49.69-101.53 kcal/mol at the CCSD(T)/cc-pVTZ//B3LYP/6-311++G(d,p) level, whereas three-membered-ring isomers c-CH2NCH, c-CH2CNH, and c-CHNHCH can be considered as metastable intermediates which can further convert into the low-lying chain-like isomers and higher lying acyclic isomers with the lowest conversion energies of 21.70-59.99 kcal/mol. Thirteen available dissociation channels depending on the different initial isomers have been identified. A prediction can be made for the possible mechanism explaining the migration of a hydrogen atom in competition with the CC bond dissociation. Several new energetically accessible pathways are found to be responsible for the migration of the hydrogen atom. The present results demonstrate that the SHS method is an efficient and powerful technique for global mapping of reaction pathways on PESs.
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Affiliation(s)
- Xia Yang
- Department of Chemistry, Graduate School of Science, Tohoku University, Aramaki, Aoba-ku, Sendai 980-8578, Japan
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