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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
    Differences between L3 and L2 x-ray absorption spectra of transition metal compounds (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6570-6576 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The differences between L3 and L2 edges of 3d and 4d transition metal complexes and compounds in octahedral symmetry are discussed. The main origin of these differences are the multiplet effects due to the coupling of the 2p core wave function and the 3d and 4d valence wave functions. The 3d and 4d spin–orbit coupling is a second origin of difference. For 3d systems the multiplet effects dominate all other interactions and the L3 and L2 edge are completely mixed and reordered. For 4d systems the core hole spin–orbit coupling is large and the L3 and L2 are separated by about 100 eV with a ratio close to 2:1. The differences between the L3 and L2 edge originate from the weight transfer between the t2g and eg peaks due to the multiplet effect. This weight transfer is about 25% for the L3 edge and about 5% for the L2 edge, which implies that for a comparison to single-particle calculations the L2 edge is preferable to use. Partly filled 4d systems are low-spin and the occupation of the t2g states implies a decrease of the first peak. This decrease is stronger for the L2 edge, implying an increase in the L3:L2 ratio. For 4d5 systems transitions to the t2g hole are only possible at the L3 edge due to the combined effects of 4d spin–orbit coupling and the dd multiplet effects.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468351
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  • 5
    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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  • 6
    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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  • 7
    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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  • 8
    Electronic Resource
    Electronic Resource
    Resonant photoemission in highly localized versus weakly localized solids (1994)
    Springer
    The European physical journal 94 (1994), S. 1-2 
    Details
    ISSN: 1434-6036
    Keywords: 79.60.Cn ; 78.70.Dm
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We report on comparative study of angle-resolved photoelectron spectra of Ni metal and CeGd at theM III andN IV,V soft-x-ray absorption threshold, respectively. OnM III resonance, the valence-band photoemission (PE) intensity of Ni follows a cos2-behavior, while the intensity of the 6-eV satellite is independent of the angle of emission relative to the E-vector of the incoming beam. On the other hand, the 4f Ce PE signal behaves ∝ cos2 onN IV,V resonance. This clearly shows that the resonant enhancement of the 6-eV PE satellite of Ni is mainly caused by an incoherent Auger decay and cannot be described as a resonant PE process.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01307645
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  • 9
    Electronic Resource
    Electronic Resource
    Resonant photoemission at the 2p thresholds of Fe, Co, and Ni metal (1994)
    Springer
    The European physical journal 95 (1994), S. 9-12 
    Details
    ISSN: 1434-6036
    Keywords: 74.70.Vy ; 78.70.Dm ; 79.60.Eq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract Resonant photoemission studies have been performed at the 2p soft-x-ray absorption thresholds of Fe, Co, and Ni metal. At resonance, the photoelectron intensity exhibits a strong enhancement in the region of the two-hole satellites, which is shown, however, to be mostly due to an incoherent superposition of a photoemission signal with a more intense signal from anL 3 M 4,5 M 4,5 Coster-Kronig decay of the core-ionized state. The resonant enhancement of the valence-band photoemission satellite in Ni metal amounts to a factor of ≃12. In contrast, no photoemission satellites are observed for Fe and Co metal.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01316837
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  • 10
    Electronic Resource
    Electronic Resource
    X-ray absorption spectroscopy study of pulsed-laser-evaporated amorphous carbon films (1995)
    Springer
    Applied physics 61 (1995), S. 111-114 
    Details
    ISSN: 1432-0630
    Keywords: 81.15.Fg ; 68.55.Nq ; 71.25.Mg ; 82.65.My
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Amorphous carbon (a-C) films obtained by pulsed-laser ablation of graphite have been investigated by X-ray Absorption Spectroscopy (XAS). The onset of 1s →σ * transitions in the films lies in the gap between theπ * andσ * bands in graphite and very close to the absorption edge of diamond, indicating a high content ofsp 3 hybridization. A sharp feature at this onset is observed and assigned to a core exciton insp 3-hybridized disordered C atoms. Its shift of 0.5 eV with respect to the core exciton in diamond is probably due to a higher localization of the excited electron induced by disorder. A small peak coming from C−H bonds at the surface is observed and its intensity inereases with the amount ofsp 3-hybridized atoms in the sample. This can be easily explained by associating a higher amount of dangling bonds at the surface to a highersp 3 content. Polarization-dependent XAS measurements show that the angular distribution of these C−H bonds has a mean value close to the normal to the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01538374
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