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Kalintsev A, Guan Q, Brugger J, Migdisov A, Etschmann B, Ram R, Liu W, Mei Y, Testemale D, Xu H. Nature and coordination geometry of geologically relevant aqueous Uranium(VI) complexes up to 400 ºC: A review and new data. JOURNAL OF HAZARDOUS MATERIALS 2023; 452:131309. [PMID: 37018892 DOI: 10.1016/j.jhazmat.2023.131309] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/22/2023] [Revised: 03/23/2023] [Accepted: 03/26/2023] [Indexed: 06/19/2023]
Abstract
The structure of the uranyl aqua ion (UO22+) and a number of its inorganic complexes (specifically, UO2Cl+, UO2Cl20, UO2SO40, [Formula: see text] , [Formula: see text] and UO2OH42-) have been characterised using X-Ray absorption spectroscopy/extended X-Ray absorption fine structure (XAS/EXAFS) at temperatures ranging from 25 to 326 ºC. Results of ab initio molecular dynamics (MD) calculations are also reported for uranyl in chloride and sulfate-bearing fluids from 25 to 400 ºC and 600 bar to 20 kilobar (kb). These results are reported alongside a comprehensive review of prior structural characterisation work with particular focus given to EXAFS works to provide a consistent and up-to-date view of the structure of these complexes under conditions relevant to U mobility in ore-forming systems and around high-grade nuclear waste repositories. Regarding reported EXAFS results, average equatorial coordination was found to decrease in uranyl and its sulfate and chloride complexes as temperature rose - the extent of this decrease differed between species and solution compositions but typically resulted in an equatorial coordination number of ∼3-4 at temperatures above 200 ºC. The [Formula: see text] complex was observed at temperatures from 25 to 247 ºC and exhibited no major structural changes over this temperature range. UO2OH42- exhibited only minor structural changes over a temperature range from 88 to 326 ºC and was suggested to manifest fivefold coordination with four hydroxyl molecules and one water molecule around its equator. Average coordination values derived from fits of the reported EXAFS data were compared to average coordination values calculated using the experimentally derived thermodynamic data for chloride complexes reported by Dargent et al. (2013) and Migdisov et al. (2018b), and for sulfate complexes reported by Alcorn et al. (2019) and Kalintsev et al. (2019). Sulfate EXAFS data were well described by available thermodynamic data, and chloride EXAFS data were described well by the thermodynamic data of Migdisov et al. (2018b), but not by the data of Dargent et al. (2013). The ab initio molecular dynamics calculations confirmed the trends in equatorial coordination observed with EXAFS and were also able to provide an insight into the effect of pressure in equatorial water coordination - for a given temperature, higher pressures appear to lead to a greater number of equatorially bound waters counteracting the temperature effect.
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Affiliation(s)
- Alexander Kalintsev
- School of Earth, Atmosphere and Environment, Monash University, 9 Rainforest Walk, VIC 3800, Australia; Los Alamos National Laboratory, Earth & Environmental Division, Los Alamos, NM, USA.
| | - Qiushi Guan
- CSIRO Mineral Resources, Kensington, WA 6151, Australia
| | - Joël Brugger
- School of Earth, Atmosphere and Environment, Monash University, 9 Rainforest Walk, VIC 3800, Australia
| | - Artas Migdisov
- Los Alamos National Laboratory, Earth & Environmental Division, Los Alamos, NM, USA
| | - Barbara Etschmann
- School of Earth, Atmosphere and Environment, Monash University, 9 Rainforest Walk, VIC 3800, Australia
| | - Rahul Ram
- School of Earth, Atmosphere and Environment, Monash University, 9 Rainforest Walk, VIC 3800, Australia
| | - Weihua Liu
- CSIRO Mineral Resources, Kensington, WA 6151, Australia
| | - Yuan Mei
- CSIRO Mineral Resources, Kensington, WA 6151, Australia
| | - Denis Testemale
- CNRS, Université Grenoble Alpes, Institut NEEL, Grenoble F-38000, France
| | - Hongwu Xu
- Los Alamos National Laboratory, Earth & Environmental Division, Los Alamos, NM, USA
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Pappalardo RR, Caralampio DZ, Martínez JM, Sánchez Marcos E. Hydration of Heavy Alkaline-Earth Cations Studied by Molecular Dynamics Simulations and X-ray Absorption Spectroscopy. Inorg Chem 2021; 60:13578-13587. [PMID: 34387993 PMCID: PMC8512670 DOI: 10.1021/acs.inorgchem.1c01888] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The physicochemical properties of the three heaviest alkaline-earth cations, Sr2+, Ba2+, and Ra2+ in water have been studied by means of classical molecular dynamics (MD) simulations. A specific set of cation-water intermolecular potentials based on ab initio potential energy surfaces has been built on the basis of the hydrated ion concept. The polarizable and flexible model of water MCDHO2 was adopted. The theoretical-experimental comparison of structural, dynamical, energetic, and spectroscopical properties of Sr2+ and Ba2+ aqueous solutions is satisfactory, which supports the methodology developed. This good behavior allows a reasonable reliability for the predicted Ra2+ physicochemical data not experimentally determined yet. Simulated extended X-ray absorption fine-structure (EXAFS) and X-ray absorption near-edge spectroscopy spectra have been computed from the snapshots of the MD simulations and compared with the experimental information available for Sr2+ and Ba2+. For the Ra2+ case, the Ra L3-edge EXAFS spectrum is proposed. Structural and dynamical properties of the aqua ions for the three cations have been obtained and analyzed. Along the [M(H2O)n]m+ series, the M-O distance for the first-hydration shell is 2.57, 2.81, and 2.93 Å for Sr2+, Ba2+, and Ra2+, respectively. The hydration number also increases when one is going down along the group: 8.1, 9.4, and 9.8 for Sr2+, Ba2+, and Ra2+, respectively. Whereas [Sr(H2O)8]2+ is a typical aqua ion with a well-defined structure, the Ba2+ and Ra2+ hydration provides a picture exhibiting an average between the ennea- and the deca-hydration. These results show a similar chemical behavior of Ba2+ and Ra2+ aqueous solutions and support experimental studies on the removal of Ra-226 of aquifers by different techniques, where Ra2+ is replaced by Ba2+. A comparison of the heavy alkaline ions, Rb+ and Cs+, with the heavy alkaline-earth ions is made.
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Affiliation(s)
- Rafael R Pappalardo
- Department of Physical Chemistry, University of Seville, 41012 Seville, Seville, Spain
| | - Daniel Z Caralampio
- Department of Physical Chemistry, University of Seville, 41012 Seville, Seville, Spain
| | - José M Martínez
- Department of Physical Chemistry, University of Seville, 41012 Seville, Seville, Spain
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Pérez-Conesa S, Martínez JM, Pappalardo RR, Marcos ES. Combining EXAFS and Computer Simulations to Refine the Structural Description of Actinyls in Water. Molecules 2020; 25:E5250. [PMID: 33187172 PMCID: PMC7697702 DOI: 10.3390/molecules25225250] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2020] [Revised: 11/05/2020] [Accepted: 11/08/2020] [Indexed: 11/16/2022] Open
Abstract
EXAFS spectroscopy is one of the most used techniques to solve the structure of actinoid solutions. In this work a systematic analysis of the EXAFS spectra of four actinyl cations, [UO2]2+, [NpO2]2+, [NpO2]+ and [PuO2]2+ has been carried out by comparing experimental results with theoretical spectra. These were obtained by averaging individual contributions from snapshots taken from classical Molecular Dynamics simulations which employed a recently developed [AnO2]2+/+ -H2O force field based on the hydrated ion model using a quantum-mechanical (B3LYP) potential energy surface. Analysis of the complex EXAFS signal shows that both An-Oyl and An-OW single scattering paths as well as multiple scattering ones involving [AnO2]+/2+ molecular cation and first-shell water molecules are mixed up all together to produce a very complex signal. Simulated EXAFS from the B3LYP force field are in reasonable agreement for some of the cases studied, although the k= 6-8 Å-1 region is hard to be reproduced theoretically. Except uranyl, all studied actinyls are open-shell electron configurations, therefore it has been investigated how simulated EXAFS spectra are affected by minute changes of An-O bond distances produced by the inclusion of static and dynamic electron correlation in the quantum mechanical calculations. A [NpO2]+-H2O force field based on a NEVPT2 potential energy surface has been developed. The small structural changes incorporated by the electron correlation on the actinyl aqua ion geometry, typically smaller than 0.07 Å, leads to improve the simulated spectrum with respect to that obtained from the B3LYP force field. For the other open-shell actinyls, [NpO2]2+ and [PuO2]2+, a simplified strategy has been adopted to improve the simulated EXAFS spectrum. It is computed taking as reference structure the NEVPT2 optimized geometry and including the DW factors of their corresponding MD simulations employing the B3LYP force field. A better agreement between the experimental and the simulated EXAFS spectra is found, confirming the a priori guess that the inclusion of dynamic and static correlation refine the structural description of the open-shell actinyl aqua ions.
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Affiliation(s)
| | | | | | - Enrique Sánchez Marcos
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain; (S.P.-C.); (J.M.M.); (R.R.P.)
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Caralampio DZ, Reeves B, Beccia MR, Martínez JM, Pappalardo RR, den Auwer C, Sánchez Marcos E. Revisiting the cobalt(II) hydration from molecular dynamics and X-ray absorption spectroscopy. Mol Phys 2019. [DOI: 10.1080/00268976.2019.1650209] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
| | - Benjamin Reeves
- Institut de Chimie de Nice, Université Côte d'Azur, CNRS, UMR 7272, Nice, France
| | - Maria R. Beccia
- Institut de Chimie de Nice, Université Côte d'Azur, CNRS, UMR 7272, Nice, France
| | - José M. Martínez
- Department of Physical Chemistry, University of Seville, Seville, Spain
| | | | - Christophe den Auwer
- Institut de Chimie de Nice, Université Côte d'Azur, CNRS, UMR 7272, Nice, France
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Zhang N, Yi H, Zeng D, Zhao Z, Wang W, Costanzo F. Structure evolution of mononuclear tungsten and molybdenum species in the protonation process: Insight from FPMD and DFT calculations. Chem Phys 2018. [DOI: 10.1016/j.chemphys.2018.01.009] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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Ayala R, Martínez JM, R Pappalardo R, Refson K, Sánchez Marcos E. Effect of Basicity on the Hydrolysis of the Bi(III) Aqua Ion in Solution: An Ab Initio Molecular Dynamics Study. J Phys Chem A 2018; 122:1905-1915. [PMID: 29376356 DOI: 10.1021/acs.jpca.7b12402] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Hydrolysis of the Bi(III) aqua ion under a range of solution conditions has been studied by means of ab initio molecular dynamics simulations. While the Bi(III) aqua ion is stable in pure water, there is an increasing degree of hydrolysis with the number of hydroxide anions in the medium. This is accompanied by a monotonic decrease of the total coordination number to an asymptotic value of ∼6, reached under extreme basicity conditions. Comparison of the simulated Bi(III) hydrolyzed species with the experimental species distribution at different degrees of basicity suggests that, at the PBE/DFT level of theory here employed, liquid water shows an overly acidic character. Predictions of theoretical EXAFS and XANES spectra were generated from the AIMD trajectories for different Bi hydrolyzed species, [Bi(HO)m(H2O)n]3-m+, m = 0-3 and n = 7-2. Comparison with available experimental spectra is presented. Spectral features joined to the degree of hydrolysis and hydration are analyzed.
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Affiliation(s)
- Regla Ayala
- Departamento Química Inorgánica, Universidad de Sevilla , 41012 Seville, Spain
| | | | | | - Keith Refson
- Royal Holloway University of London , Egham Hill, Egham, Surrey TW20 0EX, United Kingdom.,ISIS Facility, Science and Technology Facility Council , Harwell Science Campus, Didcot, OX11 0QX, United Kingdom
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Caralampio DZ, Martínez JM, Pappalardo RR, Marcos ES. The hydration structure of the heavy-alkalines Rb+ and Cs+ through molecular dynamics and X-ray absorption spectroscopy: surface clusters and eccentricity. Phys Chem Chem Phys 2017; 19:28993-29004. [DOI: 10.1039/c7cp05346k] [Citation(s) in RCA: 34] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Hydration shells around Rb+ and Cs+ are not symmetric; the cation and the 1st-shell water mass center are separated by ∼0.4 Å, and this is supported by agreement between the theoretical and experimental EXAFS spectrum.
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Affiliation(s)
| | - José M. Martínez
- Departmento de Quimica Fisica
- Universidad de Sevilla
- 41012-Seville
- Spain
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Galbis E, Hernández-Cobos J, Pappalardo RR, Marcos ES. Collecting high-order interactions in an effective pairwise intermolecular potential using the hydrated ion concept: The hydration of Cf3+. J Chem Phys 2014; 140:214104. [DOI: 10.1063/1.4879549] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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Provost K, Beret EC, Bouvet Muller D, Michalowicz A, Sánchez Marcos E. EXAFS Debye-Waller factors issued from Car-Parrinello molecular dynamics: Application to the fit of oxaliplatin and derivatives. J Chem Phys 2013; 138:084303. [DOI: 10.1063/1.4790516] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Affiliation(s)
- K Provost
- ICMPE, UMR 7182 CNRS, UPEC, PRES Paris Est, Thiais 94320, France.
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Bogatko S, Cauët E, Bylaska E, Schenter G, Fulton J, Weare J. The aqueous Ca2+ system, in comparison with Zn2+, Fe3+, and Al3+: an ab initio molecular dynamics study. Chemistry 2013; 19:3047-60. [PMID: 23315704 DOI: 10.1002/chem.201202821] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Indexed: 11/08/2022]
Abstract
Herein, we report on the structure and dynamics of the aqueous Ca(2+) system studied by using ab initio molecular dynamics (AIMD) simulations. Our detailed study revealed the formation of well-formed hydration shells with characteristics that were significantly different to those of bulk water. To facilitate a robust comparison with state-of-the-art X-ray absorption fine structure (XAFS) data, we employ a 1st principles MD-XAFS procedure and directly compare simulated and experimental XAFS spectra. A comparison of the data for the aqueous Ca(2+) system with those of the recently reported Zn(2+), Fe(3+), and Al(3+) species showed that many of their structural characteristics correlated well with charge density on the cation. Some very important exceptions were found, which indicated a strong sensitivity of the solvent structure towards the cation's valence electronic structure. Average dipole moments for the 2nd shell of all cations were suppressed relative to bulk water.
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Affiliation(s)
- Stuart Bogatko
- Chemistry and Biochemistry Department, University of California, San Diego, 9500 Gilman Dr., La Jolla, CA 92093, USA.
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GUAN QINGMEI, HAN YAN, YANG ZHONGZHI. MOLECULAR DYNAMICS STUDIES ON Fe2+, Co2+, AND Ni2+ AQUEOUS SOLUTIONS BASED ON ABEEM/MM FLUCTUATING CHARGE MODEL. JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY 2011. [DOI: 10.1142/s0219633608004519] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Based on atom-bond electronegativity equalization method fused into molecular mechanics (ABEEM/MM), the intermolecular potential for transition metal ion Fe 2+, Co 2+, and Ni 2+ cations in water has been derived. Parameters for the effective interaction between a cation and a water molecule were determined by reproducing the ab initio results. Many structural and dynamic properties of Fe 2+(aq.), Co 2+(aq.), and Ni 2+(aq.) were studied using these potential parameters. Strong influences of the twofold charged cations on the structures of the hydration shells and some other properties of aqueous ionic solutions are discussed and compared with the results of a previous study of alkali metal and alkaline-earth metal cations in water. At the same time, comparative study of the hydration properties of each cation is also discussed. This work demonstrates that ABEEM/MM provides a useful tool in the exploration of the hydration of transition metal cations in water.
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Affiliation(s)
- QING-MEI GUAN
- Department of Chemistry, Fuyang Teachers College, Fuyang 236041, PR China
| | - YAN HAN
- Department of Chemistry, Fuyang Teachers College, Fuyang 236041, PR China
| | - ZHONG-ZHI YANG
- Department of Chemistry, Liaoning Normal University, Dalian 116029, PR China
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D’Angelo P, Zitolo A, Ceccacci F, Caminiti R, Aquilanti G. Structural characterization of zinc(II) chloride in aqueous solution and in the protic ionic liquid ethyl ammonium nitrate by x-ray absorption spectroscopy. J Chem Phys 2011; 135:154509. [DOI: 10.1063/1.3653939] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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13
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D’Angelo P, Zitolo A, Migliorati V, Bodo E, Aquilanti G, Hazemann JL, Testemale D, Mancini G, Caminiti R. X-Ray absorption spectroscopy investigation of 1-alkyl-3-methylimidazolium bromide salts. J Chem Phys 2011; 135:074505. [DOI: 10.1063/1.3625920] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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14
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Cauët E, Bogatko S, Weare JH, Fulton JL, Schenter GK, Bylaska EJ. Structure and dynamics of the hydration shells of the Zn(2+) ion from ab initio molecular dynamics and combined ab initio and classical molecular dynamics simulations. J Chem Phys 2010; 132:194502. [PMID: 20499974 DOI: 10.1063/1.3421542] [Citation(s) in RCA: 80] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Results of ab initio molecular dynamics (AIMD) simulations (density functional theory+PBE96) of the dynamics of waters in the hydration shells surrounding the Zn(2+) ion (T approximately 300 K, rho approximately 1 gm/cm(3)) are compared to simulations using a combined quantum and classical molecular dynamics [AIMD/molecular mechanical (MM)] approach. Both classes of simulations were performed with 64 solvating water molecules ( approximately 15 ps) and used the same methods in the electronic structure calculation (plane-wave basis set, time steps, effective mass, etc.). In the AIMD/MM calculation, only six waters of hydration were included in the quantum mechanical (QM) region. The remaining 58 waters were treated with a published flexible water-water interaction potential. No reparametrization of the water-water potential was attempted. Additional AIMD/MM simulations were performed with 256 water molecules. The hydration structures predicted from the AIMD and AIMD/MM simulations are found to agree in detail with each other and with the structural results from x-ray data despite the very limited QM region in the AIMD/MM simulation. To further evaluate the agreement of these parameter-free simulations, predicted extended x-ray absorption fine structure (EXAFS) spectra were compared directly to the recently obtained EXAFS data and they agree in remarkable detail with the experimental observations. The first hydration shell contains six water molecules in a highly symmetric octahedral structure is (maximally located at 2.13-2.15 A versus 2.072 A EXAFS experiment). The widths of the peak of the simulated EXAFS spectra agree well with the data (8.4 A(2) versus 8.9 A(2) in experiment). Analysis of the H-bond structure of the hydration region shows that the second hydration shell is trigonally bound to the first shell water with a high degree of agreement between the AIMD and AIMD/MM calculations. Beyond the second shell, the bonding pattern returns to the tetrahedral structure of bulk water. The AIMD/MM results emphasize the importance of a quantum description of the first hydration shell to correctly describe the hydration region. In these calculations the full d(10) electronic structure of the valence shell of the Zn(2+) ion is retained. The simulations show substantial and complex charge relocation on both the Zn(2+) ion and the first hydration shell. The dipole moment of the waters in the first hydration shell is 3.4 D (3.3 D AIMD/MM) versus 2.73 D bulk. Little polarization is found for the waters in the second hydration shell (2.8 D). No exchanges were seen between the first and the second hydrations shells; however, many water transfers between the second hydration shell and the bulk were observed. For 64 waters, the AIMD and AIMD/MM simulations give nearly identical results for exchange dynamics. However, in the larger particle simulations (256 waters) there is a significant reduction in the second shell to bulk exchanges.
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Affiliation(s)
- Emilie Cauët
- Department of Chemistry and Biochemistry, University of California, San Diego, La Jolla, California 92093, USA
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Beret EC, Provost K, Müller D, Marcos ES. Coupling CP-MD Simulations and X-ray Absorption Spectroscopy: Exploring the Structure of Oxaliplatin in Aqueous Solution. J Phys Chem B 2009; 113:12343-52. [DOI: 10.1021/jp905415v] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Elizabeth C. Beret
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain, and Institut de Chimie et des Matériaux Paris Est, ICMPE/SAX, UMR 7182 CNRS, Université Paris 12, PRES Paris Est, 94320 Thiais, France
| | - Karine Provost
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain, and Institut de Chimie et des Matériaux Paris Est, ICMPE/SAX, UMR 7182 CNRS, Université Paris 12, PRES Paris Est, 94320 Thiais, France
| | - Diane Müller
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain, and Institut de Chimie et des Matériaux Paris Est, ICMPE/SAX, UMR 7182 CNRS, Université Paris 12, PRES Paris Est, 94320 Thiais, France
| | - Enrique Sánchez Marcos
- Departamento de Química Física, Universidad de Sevilla, 41012 Sevilla, Spain, and Institut de Chimie et des Matériaux Paris Est, ICMPE/SAX, UMR 7182 CNRS, Université Paris 12, PRES Paris Est, 94320 Thiais, France
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Frank P, Benfatto M, Hedman B, Hodgson KO. Solution [Cu(amm)]2+ is a Strongly Solvated Square Pyramid: A Full Account of the Copper K-edge XAS Spectrum Within Single-Electron Theory. Inorg Chem 2008; 47:4126-39. [DOI: 10.1021/ic7021243] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Patrick Frank
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
| | - Maurizio Benfatto
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
| | - Britt Hedman
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
| | - Keith O. Hodgson
- Department of Chemistry, Stanford University, Stanford, California 94305-5080, Stanford Synchrotron Radiation Laboratory, SLAC, Stanford University, Stanford, California 94309, and Laboratori Nazionali di Frascati-INFN, P.O. Box 13, 00044 Frascati, Italy
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Nichols P, Bylaska EJ, Schenter GK, de Jong W. Equatorial and apical solvent shells of the UO22+ ion. J Chem Phys 2008; 128:124507. [DOI: 10.1063/1.2884861] [Citation(s) in RCA: 75] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
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18
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Carrera F, Torrico F, Richens DT, Muñoz-Paez A, Martínez JM, Pappalardo RR, Marcos ES. Combined Experimental and Theoretical Approach to the Study of Structure and Dynamics of the Most Inert Aqua Ion [Ir(H2O)6]3+ in Aqueous Solution. J Phys Chem B 2007; 111:8223-33. [PMID: 17583938 DOI: 10.1021/jp0713716] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Quantitative determination of the hydration structure of hexaaquairidium(III), [Ir(H2O)6]3+, in aqueous solution, the most inert aqua ion known, has been achieved for the first time by a combined experimental-theoretical approach employing X-ray absorption spectroscopy and molecular dynamics (MD) simulations. The Ir LIII-edge extended X-ray absorption fine structure (EXAFS) spectrum and LI-, LII-, and LIII-edge X-ray absorption near-edge structure (XANES) spectra of three concentrations of [Ir(H2O)6]3+ in perchloric acid media were measured. To carry out classical MD simulations of the aqua ion in water, a new set of first-principles Ir-H2O intermolecular potentials, based on the hydrated ion concept, has been developed. Structural, dynamics, and energetic properties have been obtained from the analysis of the statistical trajectories generated. The Ir-O radial distribution function shows two well-defined peaks at 2.04 +/- 0.01 and 4.05 +/- 0.05 A corresponding to the first and second hydration shell, respectively; the fundamental frequencies for the aqua ion in water are well reproduced by the MD simulation, and its dynamic properties are similar to the experimental values corresponding to other hexahydrated trivalent ions. Particular attention has been devoted to the experimental determination of the second hydration shell. It has been found that contrarily to what expected on the basis of the inertness of the Ir3+ aquaion, the detection of the second hydration shell by EXAFS for this cation is more difficult than for others less inert aqua ions such as Cr3+ or Rh3+. But when combined with MD simulations it is possible to confirm the coordination distance for this shell at 4.1 +/- 0.1 A. In addition, the computation of LI, LII and LIII XANES spectra were carried out using the structural information obtained from MD. These computations allowed the assignment of special features of the spectra to the second hydration shell on a quantitative basis. Therefore, interestingly XANES spectra have given a stronger support to the second hydration shell than EXAFS. The fit of the LIII-edge EXAFS gives an accurate description of the first hydration shell structure in aqueous solution. The value for Ir-O first shell is 2.04 +/- 0.01 A. The statistical information available with the MD results has allowed the analysis of the standard deviation associated with the computation of the XANES spectrum. It is shown that the standard deviation increases with the number of hydration shells and this increase is nonuniform along the average spectrum.
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Affiliation(s)
- Flora Carrera
- Departamento de Química InorgAnica, ICMSE, CSIC, Universidad de Sevilla, 41012 Sevilla, Spain
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Guan QM, Yang ZZ. Theoretical Study on Co3+ in Aqueous Solution in Terms of ABEEM/MM Model. CHINESE J CHEM 2007. [DOI: 10.1002/cjoc.200790136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
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20
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Spezia R, Duvail M, Vitorge P, Cartailler T, Tortajada J, Chillemi G, D'Angelo P, Gaigeot MP. A Coupled Car-Parrinello Molecular Dynamics and EXAFS Data Analysis Investigation of Aqueous Co2+. J Phys Chem A 2006; 110:13081-8. [PMID: 17134169 DOI: 10.1021/jp064688z] [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: 02/05/2023]
Abstract
We have studied the microscopic solvation structure of Co(2+) in liquid water by means of density functional theory (DFT)-based Car-Parrinello molecular dynamics (CPMD) simulations and extended X-ray absorption fine structure (EXAFS) data analysis. The effect of the number of explicit water molecules in the simulation box on the first and second hydration shell structures has been considered. Classical molecular dynamics simulations, using an effective two-body potential for Co(2+)-water interactions, were also performed to show box size effects in a larger range. We have found that the number of explicit solvent molecules has a marginal role on the first solvation shell structural parameters, whereas larger boxes may be necessary to provide a better description of the second solvation shell. Car-Parrinello simulations were determined to provide a reliable description of structural and dynamical properties of Co(2+) in liquid water. In particular, they seem to describe both the first and second hydration shells correctly. The EXAFS signal was reconstructed from Car-Parrinello simulations. Good agreement between the theoretical and experimental signals was observed, thus strengthening the microscopic picture of the Co(2+) solvation properties obtained using first-principle simulations.
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Affiliation(s)
- Riccardo Spezia
- Laboratoire Analyse et Modélisation pour la Biologie et l'Environnement, UMR-CNRS 8587, Université d'Evry Val d'Essonne, Boulevard F. Mitterrand, 91025 Evry Cedex, France
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21
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Dang LX, Schenter GK, Glezakou VA, Fulton JL. Molecular Simulation Analysis and X-ray Absorption Measurement of Ca2+, K+and Cl-Ions in Solution. J Phys Chem B 2006; 110:23644-54. [PMID: 17125322 DOI: 10.1021/jp064661f] [Citation(s) in RCA: 94] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
This paper presents recent advances in the use of molecular simulations and extended X-ray absorption fine structure (EXAFS) spectroscopy, which enable us to understand solvated ions in solution. We report and discuss the EXAFS spectra and related properties governing solvation processes of different ions in water and methanol. Molecular dynamics (MD) trajectories are coupled to electron scattering simulations to generate the MD-EXAFS spectra, which are found to be in very good agreement with the corresponding experimental measurements. From these simulated spectra, the ion-oxygen distances for the first hydration shell are in agreement with experiment within 0.05-0.1 A. The ionic species studied range from monovalent to divalent, positive and negative: K+, Ca2+, and Cl-. This work demonstrates that the combination of MD-EXAFS and the corresponding experimental measurement provides a powerful tool in the analysis of the solvation structure of aqueous ionic solutions. We also investigate the value of electronic structure analysis of small aqueous clusters as a benchmark to the empirical potentials. In a novel computational approach, we determine the Debye-Waller factors for Ca2+, K+, and Cl- in water by combining the harmonic analysis of data obtained from electronic structure calculations on finite ion-water clusters, providing excellent agreement with the experimental values, and discuss how they compare with results from a harmonic classical statistical mechanical analysis of an empirical potential.
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Affiliation(s)
- Liem X Dang
- Chemical Sciences Division, Pacific Northwest National Laboratory, Richland, Washington 99352, USA
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22
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Ayala R, Martínez JM, Pappalardo RR, Muñoz-Páez A, Sánchez Marcos E. The solvation of bromide anion in acetonitrile: a structural study based on the combination of theoretical calculations and X-ray absorption spectroscopy. MOLECULAR SIMULATION 2006. [DOI: 10.1080/08927020601089064] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
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23
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Gutowski KE, Dixon DA. Predicting the Energy of the Water Exchange Reaction and Free Energy of Solvation for the Uranyl Ion in Aqueous Solution. J Phys Chem A 2006; 110:8840-56. [PMID: 16836448 DOI: 10.1021/jp061851h] [Citation(s) in RCA: 150] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The structures and vibrational frequencies of UO2(H2O)4(2+) and UO2(H2O)5(2+) have been calculated using density functional theory and are in reasonable agreement with experiment. The energies of various reactions were calculated at the density functional theory (DFT) and MP2 levels; the latter provides the best results. Self-consistent reaction field calculations in the PCM and SCIPCM approximations predicted the free energy of the water exchange reaction, UO2(H2O)4(2+) + H2O <--> UO2(H2O)5(2+). The calculated free energies of reaction are very sensitive to the choice of radii (O and H) and isodensity values in the PCM and SCIPCM models, respectively. Results consistent with the experimental HEXS value of -1.19 +/- 0.42 kcal/mol (within 1-3 kcal/mol) are obtained with small cavities. The structures and vibrational frequencies of the clusters with second solvation shell waters: UO2(H2O)4(H2O)8(2+), UO2(H2O)4(H2O)10(2+), UO2(H2O)4(H2O)11(2+), UO2(H2O)5(H2O)7(2+), and UO2(H2O)5(H2O)10(2+), were calculated and are in better agreement with experiment as compared to reactions involving only UO2(H2O)4(2+) and UO2(H2O)5(2+). The MP2 reaction energies for water exchange gave gas-phase results that agreed with experiment in the range -5.5 to +3.3 kcal/mol. The results were improved by inclusion of a standard PCM model with differences of -1.2 to +2.7 kcal/mol. Rearrangement reactions based on an intramolecular isomerization leading to a redistribution of water in the two shells provide good values in comparison to experiment with values of Delta G(exchange) from -2.2 to -0.5 kcal/mol so the inclusion of a second hydration sphere accounts for most solvation effects. Calculation of the free energy of solvation of the uranyl cation yielded an upper bound to the solvation energy of -410 +/- 5 kcal/mol, consistent with the best experimental value of -421 +/- 15 kcal/mol.
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Affiliation(s)
- Keith E Gutowski
- Department of Chemistry and Center for Green Manufacturing, Shelby Hall, Box 870336, The University of Alabama, Tuscaloosa, Alabama 35487, USA
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Chaboy J, Muñoz-Páez A, Merkling PJ, Sánchez Marcos E. The hydration of Cu2+: Can the Jahn-Teller effect be detected in liquid solution? J Chem Phys 2006; 124:64509. [PMID: 16483222 DOI: 10.1063/1.2165189] [Citation(s) in RCA: 98] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The long elusive structure of Cu(II) hydrate in aqueous solutions, classically described as a Jahn-Teller distorted octahedron and recently proposed to be a fivefold coordination structure [Pasquarello et al., Science 291, 856 (2001)], has been probed with x-ray-absorption spectroscopy by performing a combined theoretical and experimental analysis. Two absorption channels were needed to obtain a proper reproduction of the x-ray-absorption near-edge structure (XANES) region spectrum, as already observed in other Cu(II) complexes [Chaboy et al., Phys. Rev. B 71, 134208 (2005)]. The extended x-ray-absorption fine-structure (EXAFS) spectrum was analyzed as well within this approach. Quite good reproductions of both XANES and EXAFS spectra were attained for several distorted and undistorted structures previously proposed. Nevertheless, there is not a clearly preferred structure among those including four-, five-, and sixfold coordinated Cu(II) ions. Taking into account our results, as well as many more from several other authors using different techniques, the picture of a distorted octahedron for the Cu(II) hexahydrate in aqueous solution, paradigm of the Jahn-Teller effect, is no longer supported. In solution a dynamical view where the different structures exchange among themselves is the picture that better suits the results presented here.
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Affiliation(s)
- Jesús Chaboy
- Instituto de Ciencia de Materiales de Aragón, CSIC-Universidad de Zaragoza, Spain
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25
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Hydration Structure and Dynamic Properties of the Square Planar Pt(II) Aquaion Compared to the Pd(II) Case. Theor Chem Acc 2005. [DOI: 10.1007/s00214-005-0059-z] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/25/2022]
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Purans J, Fourest B, Cannes C, Sladkov V, David F, Venault L, Lecomte M. Structural Investigation of Pd(II) in Concentrated Nitric and Perchloric Acid Solutions by XAFS. J Phys Chem B 2005; 109:11074-82. [PMID: 16852349 DOI: 10.1021/jp045489n] [Citation(s) in RCA: 59] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
XAFS spectra of palladium(II) in concentrated HNO3/HClO4 acid mixtures have been recorded and analyzed. Structural parameters of the Pd(H2O)4(2+) complex and the mixed nitric Pd(NO3)2(H2O)2 complex, for the first time, were determined by the XAFS method. For pure 5 M HClO4 and for mixtures (0-0.3 M HNO3), the XAFS spectra of the 0.02 M Pd solutions are indeed very similar and originated from four Pd-O(w) equivalent distances. For the Pd(H2O)4(2+) square-planar aqua ion in strong perchloric acid, the use of an FEFF6 theoretical approach led to a first-shell Pd-O(w) distance of 2.00 (1) A and a Debye-Waller (DW) factor of sigma2 = 0.0030 (3) A2. Four water molecules are tightly bound to the Pd2+ ion in the equatorial plane, while two (or one) axial water molecules are weakly bound to the metal ion at 2.5 A with a DW factor of 0.015 (5) A2. For highly concentrated mixtures (4-6 M HNO3) and for pure concentrated (4-6 M) nitric acid as well as for crystalline powder Pd(NO3)2(H2O)2, the XAFS spectra are very similar and are determined by the mixed nitric complex Pd(NO3)2(H2O)2: four Pd-O near-equivalent distances of 2.01 (1) A from two H2O and two NO3 molecules with a total DW factor of sigma2 = 0.0037 (3) A2. Moreover, two Pd---N distances of 2.8-2.9 A were determined in the second coordination shell. Finally, for intermediate mixtures (1-3 M HNO3 in 5 M HClO4), the XAFS spectra are a superposition of the XAFS of Pd(H2O)4(2+) and Pd(NO3)2(H2O)2 complexes. The mean ligand number NO3(-) around Pd2+ has been calculated, and the XAFS results at pH close to zero confirm the spectrophotometric results previously published.
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Affiliation(s)
- J Purans
- Institut de Physique Nucléaire, 91406 Orsay Cedex, France.
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27
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Boyanov MI, Kemner KM, Shibata T, Bunker BA. Local Structure around Cr3+ Ions in Dilute Acetate and Perchlorate Aqueous Solutions. J Phys Chem A 2004. [DOI: 10.1021/jp049444y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Maxim I. Boyanov
- Environmental Research, Argonne National Laboratory, Argonne, Illinois 60439, and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556
| | - Kenneth M. Kemner
- Environmental Research, Argonne National Laboratory, Argonne, Illinois 60439, and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556
| | - Tomohiro Shibata
- Environmental Research, Argonne National Laboratory, Argonne, Illinois 60439, and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556
| | - Bruce A. Bunker
- Environmental Research, Argonne National Laboratory, Argonne, Illinois 60439, and Department of Physics, University of Notre Dame, Notre Dame, Indiana 46556
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Chen K, Yuldasheva S, Penner-Hahn JE, O'Halloran TV. An atypical linear Cu(I)-S2 center constitutes the high-affinity metal-sensing site in the CueR metalloregulatory protein. J Am Chem Soc 2004; 125:12088-9. [PMID: 14518983 DOI: 10.1021/ja036070y] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
CueR is a copper-responsive genetic switch that regulates transcription of genes encoding the primary copper-exporting system in E. coli, CopA and CueO. Although a member of the MerR family of regulatory proteins, CueR has four cysteines in an array that is distinct from those in Hg(II)-sensing MerR or in Zn-sensing ZntR. A recent crystal structure showed one copper atom in CueR bound to cysteines Cys112 and Cys120 in a linear CuS2 structure, but left open the questions of whether the other half of the CueR dimer has the same structure, and of whether these structures depend on the two additional C-terminal cysteines. Metal binding, transcription runoff, and cysteine modification studies show that only Cys112 and Cys 120 are necessary and sufficient to make the transcriptionally active Cu-sensing site. X-ray absorption spectroscopy shows that this site binds Cu(I) in a strictly linear CuS2 site in solution, a structure that is rarely observed in copper proteins. This structure does not depend either on additional metal loading or upon the presence of additional C-terminal cysteine ligands and is well suited for an ultrasensitve receptor site that discriminates against the binding of other metal ions.
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Affiliation(s)
- Kui Chen
- Department of Chemistry, Northwestern University, Evanston, Illinois 60208, USA
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30
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Merkling PJ, Ayala R, Martı́nez JM, Pappalardo RR, Sánchez Marcos E. Interplay of computer simulations and x-ray absorption spectra in the study of the bromide hydration structure. J Chem Phys 2003. [DOI: 10.1063/1.1603719] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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31
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Merkling PJ, Muñoz-Páez A, Sánchez Marcos E. Exploring the capabilities of X-ray absorption spectroscopy for determining the structure of electrolyte solutions: computed spectra for Cr(3+) or Rh(3+) in water based on molecular dynamics. J Am Chem Soc 2002; 124:10911-20. [PMID: 12207547 DOI: 10.1021/ja025729h] [Citation(s) in RCA: 65] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Extended X-ray absorption fine structure (EXAFS) spectra of Cr(3+) and Rh(3+) in aqueous solution are analyzed and compared with computed spectra derived from structural results obtained by molecular dynamics (MD) simulation. This procedure quantifies the reliability of the EXAFS structural determination when applied to ions in solution. It provides guidelines for interpreting experimental spectra of octahedrally coordinated metal cations in aqueous solution. A set of relationships among Debye-Waller factors is proposed on the basis of MD results to reduce the number of independent fit parameters. The determination of the second hydration shell is examined. Calculated XANES spectra compare well with experimental ones. Indeed, the splitting observed on the main peak of the Rh K-edge was anticipated by the calculations. Simulated spectra from MD structures of increasing cluster size show a relationship between the second hydration shell and features of the XANES region at energies just above the edge. The combination of quantum and statistical calculations with the XANES spectrum is found to be very fruitful to get insight into the quantitative estimation of structural properties of electrolyte solutions.
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Affiliation(s)
- Patrick J Merkling
- Departamento de Química Física, Universidad de Sevilla-CSIC, 41012 Seville, Spain
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32
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D'Angelo P, Barone V, Chillemi G, Sanna N, Meyer-Klaucke W, Pavel NV. Hydrogen and higher shell contributions in Zn2+, Ni2+, and Co2+ aqueous solutions: an X-ray absorption fine structure and molecular dynamics study. J Am Chem Soc 2002; 124:1958-67. [PMID: 11866609 DOI: 10.1021/ja015685x] [Citation(s) in RCA: 155] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
A detailed investigation of the hydration structure of Zn2+, Ni2+, and Co2+ in water solutions has been carried out combining X-ray absorption fine structure (EXAFS) spectroscopy and Molecular Dynamics (MD) simulations. The first quantitative analysis of EXAFS from hydrogen atoms in 3d transition metal ions in aqueous solutions has been carried out and the ion-hydrogen interactions have been found to provide a detectable contribution to the EXAFS spectra. An accurate determination of the structural parameters associated with the first hydration shell has been performed and compared with previous experimental results. No evidence of significant contributions from the second hydration shell to the EXAFS signal has been found for these solutions, while the inclusion of the hydrogen signal has been found to be important in performing a quantitative analysis of the experimental data. The high-frequency contribution present in the EXAFS spectra has been found to be due to multiple scattering (MS) effects inside the ion-oxygen first coordination shell. MD has been used to generate three-body distribution functions from which a reliable analysis of the MS contributions to the EXAFS spectra of these systems has been carried out.
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Affiliation(s)
- Paola D'Angelo
- Dipartimento di Chimica, Università di Roma La Sapienza, P. le A. Moro 5, 00185 Roma, Italy
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Ayala R, Marcos ES, Díaz-Moreno S, Solé VA, Muñoz-Páez A. Geometry and Hydration Structure of Pt(II) Square Planar Complexes [Pt(H2O)4]2+and [PtCl4]2-as Studied by X-ray Absorption Spectroscopies and Quantum-Mechanical Computations. J Phys Chem B 2001. [DOI: 10.1021/jp010326+] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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34
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Spångberg D, Hermansson K, Lindqvist-Reis P, Jalilehvand F, Sandström M, Persson I. Model Extended X-ray Absorption Fine Structure (EXAFS) Spectra from Molecular Dynamics Data for Ca2+ and Al3+ Aqueous Solutions. J Phys Chem B 2000. [DOI: 10.1021/jp000247i] [Citation(s) in RCA: 44] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
| | | | | | | | | | - Ingmar Persson
- Department of Chemistry, Swedish University of Agricultural Sciences, P.O. Box 7015, S-750 07 Uppsala, Sweden
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Muñoz-Páez A, Díaz-Moreno S, Sánchez Marcos E, Rehr JJ. Importance of multiple-scattering phenomena in XAS structural determinations of [Ni(CN)4]2- in condensed phases. Inorg Chem 2000; 39:3784-90. [PMID: 11196770 DOI: 10.1021/ic000274n] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A quantitative analysis of the XAS spectra of the tetracyanonickelate complex [Ni(CN)4]2- has been carried out. The simultaneous study of the EXAFS and XANES regions yielded complementary information regarding the geometric and electronic structures of the complex. XANES spectra were modeled by applying recently developed self-consistent, full multiple-scattering algorithms in the FEFF8 code (version 8 x 34). XANES spectra for clusters of different sizes (from 9 to 125 atoms) were computed and compared with experimental spectra. This region of the spectra was proportional to a broadened Ni p-density of states diagram above the Fermi level. Although the main features of the XANES spectra were reasonably reproduced by computations, the weak dependence of the theoretical spectra on cluster size contrasts with the close similarity between the experimental spectra of the solid and solution systems. Because of the special geometry of the complex, calculations with polarized light parallel and perpendicular to the molecular plane were carried out, yielding a reasonable reproduction of the experimental data from another report for cluster sizes equal to or higher than 45 atoms. The highly symmetric square planar structure of the complex was found to be responsible for the unusual amplitude of the multiple-scattering (MS) contributions to the EXAFS spectra. Spectra in this region were fitted using the FEFFIT EXAFS analysis program, taking into account only the MS paths that simultaneously have both a high amplitude, as calculated with the ab initio code FEFF, and a small Debye-Waller factor, as estimated by the independent-vibration approximation model. Fitting results yielded very similar structures for the Ni2+ complex in the solid state and in solution, though the larger Debye-Waller factors found for the solid suggest higher static disorder in this state.
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Affiliation(s)
- A Muñoz-Páez
- Instituto de Ciencia de Materiales and Departamento de Química Inorgánica, CSIC-Universidad de Sevilla, c/Américo Vespucio s/n, 41092 Sevilla, Spain.
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