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  • 1
    Electronic Resource
    Electronic Resource
    Ab Initio Analysis of Water-Assisted Reaction Mechanisms in Amide Hydrolysis (1994)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 116 (1994), S. 3912-3921 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00088a030
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  • 2
    Electronic Resource
    Electronic Resource
    Solvent effects on the mechanism and selectivities of asymmetric Diels-Alder reactions (1993)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 115 (1993), S. 8780-8787 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00072a035
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular dynamics simulation of formamide in water using density functional theory and classical potentials (1999)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 111 (1999), S. 1117-1125 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the first molecular dynamics simulation of an amide in water in which the solute is fully described through quantum mechanics methods (density functional theory in our case). All solute's degrees of freedom are allowed to vary. The solvent is described through a classical potential. We have chosen for our study the simple formamide molecule since it allows hybrid simulations to be carried out at a sophisticated quantum level. More precisely, we have considered two computational schemes: in the first one, we use a small double-ζ basis set and a local approximation of the exchange-correlation functional whereas, in the second, an extended triple-ζ+polarization basis set, as well as a gradient-corrected functional, has been employed. The analysis of the results is focused on both structural and energetic aspects. Particular attention is paid to the time variation of dihedral angles in formamide connected to nitrogen pyramidalization and NH2 subunit rotation. The agreement with available experimental and theoretical data is satisfactory. Nevertheless, the limits of the method are pointed out, in particular the need to improve the description of the nonelectrostatic term of the solute-solvent interaction potential. One of the main advantages of the hybrid approach is that polarization effects are included in a rigorous manner. This renders possible a detailed discussion on the role of hydration effects on amides structure, a point of considerable relevance due to the biochemical importance of the peptidic bond. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.479299
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  • 4
    Electronic Resource
    Electronic Resource
    Symmetry and Cluster Size Effects in XANES Spectra (1995)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 99 (1995), S. 16499-16499 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100044a046
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  • 5
    Electronic Resource
    Electronic Resource
    Nonequilibrium solvent effects on the SN2 reaction using a self-consistent reaction field continuum model based on multipole expansions (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 9249-9260 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple model has been developed that allows analysis of nonequilibrium solvent effects on chemical processes. It is based on the use of a self-consistent reaction field approach using a multipole development of the solvation energy and on the separation of the inertial and noninertial polarization of the solvent. The solute's wave function is computed at the ab initio level. The main advantage with respect to previously reported models is that the inclusion of nonequilibrium or dynamic solvent effects are introduced through the definition of a single solvent coordinate which is related to the chemical system coordinates. Besides, inclusion of polarization effects is straightforward. Results are presented for the SN2 reaction F−+CH3F→FCH3+F−. The frozen-solvent hypothesis and the role of solvent fluctuations are discussed. It is shown that the climb to the transition barrier must be preceded by a convenient fluctuation of the solvent so that its inertial polarization component is suitable to solvate the transition state. Other solvent fluctuations, energetically less favorable, could decrease or even suppress the transition barrier. Nonequilibrium solvation effects on the value of the transmission coefficient are discussed. The methodology proposed in this work may be extended to the study of other rapid processes in solution such as proton transfers or electronic excitations. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469985
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  • 6
    Electronic Resource
    Electronic Resource
    Water dimer in liquid water (1992)
    Springer
    Theoretical chemistry accounts 84 (1992), S. 181-194 
    Details
    ISSN: 1432-2234
    Keywords: Water dimer ; Self-consistent reaction field ; Cooperative phenomenon ; Liquid state ; Water-water potential
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary A Self-Consistent Reaction Field Model is used to study the effect of the molecular environment on the electronic distribution and on the equilibrium geometry of the water dimer in liquid water. Computations are performed at the 6-311G++(2d,2p) MP2 level. Comparison of the results for the monomer and the dimer, in a vacuum and in the liquid, is made in order to gain a deeper insight on the cooperative phenomenon. The discussion emphasizes the trends which should be considered for deriving more sophisticated water-water potentials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01113207
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  • 7
    Electronic Resource
    Electronic Resource
    A multiple-scattering approach to the study of X-ray absorption spectra of anatase and rutile (1993)
    Springer
    Catalysis letters 20 (1993), S. 59-71 
    Details
    ISSN: 1572-879X
    Keywords: EXAFS ; XANES ; TiO2 ; multiple scattering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Theoretical computations of the X-ray absorption spectra of the crystalline forms of TiO2, rutile and anatase, have been carried out in order to analyze the influence of multiple scattering contributions to the absorption coefficient. The cluster size used in the computations after making a detailed study of shell contributions, has been 75 atoms for rutile and 63 for anatase. This work has been envisaged as a suitable starting point to the analysis of experimental data for the more complicated TiO2 amorphous systems involved in catalytic processes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00772597
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  • 8
    Electronic Resource
    Electronic Resource
    2-Nitroethanal conformations in solution: AnAb initio SCRF study (1994)
    Springer
    Structural chemistry 5 (1994), S. 357-360 
    Details
    ISSN: 1572-9001
    Keywords: Cavity model ; solvent effect ; ab initio ; 2-nitroethanal
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The structure of 2-nitroethanal has been studied at the MP2/6-31G* level in the gas phase and in acetonitrile using a continuum model to represent the electrostatic solute-solvent interactions. The relative energies of the two stable conformations obtained are quite dependent on the media. Indeed, our computations predict a change of the most stable conformation from gas to polar solvent. These results are in agreement with experimental data for the axial/equatorial conformational equilibrium of 2-nitrocyclohexanone.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02252893
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  • 9
    Electronic Resource
    Electronic Resource
    A density functional study of pseudotetrahedral metal-nitrosyl complexes (1994)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 52 (1994), S. 1039-1049 
    Details
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Local and nonlocal density functional computations have been carried out to study the electronic structure and the equilibrium geometry of the isoelectronic series Cr(NC)4, Mn(NO)3(CO), Fe(NO)2(CO)2, and Co(NO)(CO)3 and model compounds Fe(NO)2L2 (L = Cl, HCN, NH3, PH3, and C2H4). The structure of Fe(NO)2(C4H6) is also described. The discussion is focused on structural modifications through a change of ligand, in particular those concerning the metal-nitrosyl conformation (linear vs. bent). Though this is a preliminary study of metal-nitrosyl properties by DFT methods and more computations are required to analyze the mechanism of homogeneous catalysis processes, our results support the hypothesis that structural reorganization from linear to bent metal-nitrosyl plays a key role in some reactions, such as in butadiene dimerization. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/qua.560520429
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  • 10
    Electronic Resource
    Electronic Resource
    Influence of environment on proton-transfer mechanisms in model triads from theoretical calculations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1675-1688 
    Details
    ISSN: 0192-8651
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We have carried out theoretical calculations to analyze molecular interactions and proton transfer mechanisms in the formate-imidazole-water system, which may be considered the simplest model of catalytic triads in serine proteases. Computations were carried out at the density functional theory level. The effect of a dielectric environment on energy surfaces is considered using a polarizable continuum model and the self-consistent reaction field approach. The role played by inertial and noninertial polarization of this environment is emphasized. Nonequilibrium solvation effects have been estimated. The results show that there are different reaction mechanisms, concerted or stepwise, that may be competitive, depending on the nature of the molecular environment.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1675-1688, 1998
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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