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Dang LX Schenter GK Glezakou VA Fulton JL 《The journal of physical chemistry. B》2006,110(47):23644-23654
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. 相似文献
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Vassiliki-Alexandra Glezakou Yongsheng Chen John L. Fulton Gregory K. Schenter Liem X. Dang 《Theoretical chemistry accounts》2006,115(2-3):86-99
We investigate the solvation structure of aqueous potassium ions, using a combination of electronic structure calculations,
statistical mechanical simulations with a derived polarizable empirical potential and experimental measurement of the extended
X-ray absorption fine structure (EXAFS) spectra. The potassium K-edge (at 3,608 eV) EXAFS spectra were acquired on the bending
magnet of sector 20 at the Advanced Photon Source, at ambient conditions and for the concentrations of 1 and 4 m KCl. We focus
on the coordination distances and the degree of disorder of the first hydration shell as determined by electronic structure
calculations, molecular dynamics simulations and experimental measurement. Finally, we characterize the changes of the structure
in the first hydration shell with increasing temperature as predicted by molecular simulation 相似文献
3.
Aqueous complexation, adsorption, and redox chemistry of actinide species at mineral surfaces have a significant impact on their transport and reactive behavior in chemically and physically heterogeneous environments. The adsorption configurations and energies of microsolvated uranyl dication species, UO(2)(H(2)O)(n)(2+), were determined on fully hydroxylated and proton-deficient α-alumina(0001)-like finite cluster models. The significant size of the models provides faithful representations of features that have emerged from periodic calculations, but most importantly, they afford us a systematic study of the adsorption mechanism, the effect of secondary solvation shells and an explicit treatment of the total charge. Based on this cluster representation, the energetics computed from the difference between the optimized structures and the appropriate reference states point to a preference for an inner-sphere type complex. 相似文献
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Katherine Koh Udishnu Sanyal Mal‐Soon Lee Guanhua Cheng Miao Song Vassiliki‐Alexandra Glezakou Yue Liu Dongsheng Li Roger Rousseau Oliver Y. Gutirrez Abhijeet Karkamkar Miroslaw Derewinski Johannes A. Lercher 《Angewandte Chemie (International ed. in English)》2020,59(4):1501-1505
Acid functionalization of a carbon support allows to enhance the electrocatalytic activity of Pd to hydrogenate benzaldehyde to benzyl alcohol proportional to the concentration of Brønsted‐acid sites. In contrast, the hydrogenation rate is not affected when H2 is used as a reduction equivalent. The different responses to the catalyst properties are shown to be caused by differences in the hydrogenation mechanism between the electrochemical and the H2‐induced hydrogenation pathways. The enhancement of electrocatalytic reduction is realized by the participation of support‐generated hydronium ions in the proximity of the metal particles. 相似文献
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Dr. Katherine Koh Dr. Udishnu Sanyal Dr. Mal-Soon Lee Dr. Guanhua Cheng Dr. Miao Song Dr. Vassiliki-Alexandra Glezakou Dr. Yue Liu Dr. Dongsheng Li Dr. Roger Rousseau Dr. Oliver Y. Gutiérrez Dr. Abhijeet Karkamkar Dr. Miroslaw Derewinski Prof. Johannes A. Lercher 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2020,132(4):1517-1521
Acid functionalization of a carbon support allows to enhance the electrocatalytic activity of Pd to hydrogenate benzaldehyde to benzyl alcohol proportional to the concentration of Brønsted-acid sites. In contrast, the hydrogenation rate is not affected when H2 is used as a reduction equivalent. The different responses to the catalyst properties are shown to be caused by differences in the hydrogenation mechanism between the electrochemical and the H2-induced hydrogenation pathways. The enhancement of electrocatalytic reduction is realized by the participation of support-generated hydronium ions in the proximity of the metal particles. 相似文献
6.
Windisch CF Glezakou VA Martin PF McGrail BP Schaef HT 《Physical chemistry chemical physics : PCCP》2012,14(8):2560-2566
We report the first Raman spectra of fully (18)O-labeled supercritical CO(2) (scCO(2)) and various isotopic mixtures. The experimental results, coupled with ab initio molecular dynamics calculations, demonstrate that the frequencies assigned to the Fermi dyad of the CO(2) molecule transpose upon isotopic labeling of both oxygen atoms. Although the transposition of the Fermi dyad of CO(2) gas due to isotopic substitution has been discussed before, this is the first confirmation of the effect in the Raman spectrum of the supercritical fluid and provides necessary groundwork for future Raman spectroscopy studies of reactions in this important medium. More importantly, the work yields a quantitative assessment of the mixing of states upon labeling that provides the needed clarification concerning the pedigree of the assignments for the dyad of CO(2) under supercritical conditions. 相似文献
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Vassiliki‐Alexandra Glezakou Maria Soutzidou Christos Loukoutos Ioannis Xexakis Kyriakos G. Viras 《Journal of Polymer Science.Polymer Physics》1999,37(13):1351-1356
The polymer polyvinylchloride has been studied in binary solvent mixtures and as a function of temperature in solution. A discontinuity of the polymer chain dimensions has been observed, as measured by hydrodynamic methods. This phenomenon is further examined by infrared and Raman spectroscopy. © 1999 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 37: 1351–1356, 1999 相似文献
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Udishnu Sanyal Simuck F. Yuk Katherine Koh Mal‐Soon Lee Kelsey Stoerzinger Difan Zhang Laura C. Meyer Juan A. Lopez‐Ruiz Abhi Karkamkar Jamie D. Holladay Donald M. Camaioni Manh‐Thuong Nguyen Vassiliki‐Alexandra Glezakou Roger Rousseau Oliver Y. Gutirrez Johannes A. Lercher 《Angewandte Chemie (International ed. in English)》2021,60(1):290-296
The hydrogenation of benzaldehyde to benzyl alcohol on carbon‐supported metals in water, enabled by an external potential, is markedly promoted by polarization of the functional groups. The presence of polar co‐adsorbates, such as substituted phenols, enhances the hydrogenation rate of the aldehyde by two effects, that is, polarizing the carbonyl group and increasing the probability of forming a transition state for H addition. These two effects enable a hydrogenation route, in which phenol acts as a conduit for proton addition, with a higher rate than the direct proton transfer from hydronium ions. The fast hydrogenation enabled by the presence of phenol and applied potential overcompensates for the decrease in coverage of benzaldehyde caused by competitive adsorption. A higher acid strength of the co‐adsorbate increases the intensity of interactions and the rates of selective carbonyl reduction. 相似文献
9.
Structure and thermodynamics of carbon and carbon/silicon precursors to nanostructures 总被引:1,自引:0,他引:1
The structures at the Hartree-Fock level, as well as the energetics, are reported for the unsaturated system C(36)H(16), its Si-doped analogue C(32)Si(4)H(16), and several smaller, unsaturated fragments. Structural effects on the electronic distribution are discussed in terms of a localized orbital energy decomposition. The standard heats of formation are calculated based on homodesmic and isodesmic reactions and the G2(MP2,SVP) method with a valence double-zeta plus polarization basis. The origin of the observed explosion of the all-carbon system (C(36)H(16)) to form carbon nanotubes was investigated by exploring a possible initial reactive channel (dimerization), which could lead to the formation of the observed onion-type nanostructures. 相似文献
10.
Dr. Guoju Yang Dr. Sneha A. Akhade Xi Chen Dr. Yue Liu Dr. Mal‐Soon Lee Dr. Vassiliki‐Alexandra Glezakou Dr. Roger Rousseau Prof. Dr. Johannes A. Lercher 《Angewandte Chemie (Weinheim an der Bergstrasse, Germany)》2019,131(11):3565-3570
The thermodynamic state of H2 adsorbed on Pt in the aqueous phase was determined by kinetic analysis of H2 reacting with D2O to HDO, HD, and D2, and by DFT‐based ab initio molecular dynamics simulations of H2 adsorption on Pt(111), Pt(110), and Pt nanoparticles. Dissociative adsorption of H2 on Pt is significantly weakened in the aqueous phase compared to adsorption at gas–solid interfaces. Water destabilizes the adsorbed H atoms, decreasing the heat of adsorption by 19–22 kJ while inducing an additional entropy loss of 50–70 J K?1. Upon dissociative adsorption of H2, the average distance of water from the Pt surface increases and the liquid adopts a structure that is more ordered than before close to the Pt surface, which limits the translation mobility of the adsorbed H atoms. The presence of hydrated hydronium ions next to the Pt surface further lowers the H?Pt bond strength. 相似文献
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