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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical Calculation of the Water Ion Product KW (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 1625-1628 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00110a019
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  • 2
    Electronic Resource
    Electronic Resource
    Cavities in molecular liquids and the theory of hydrophobic solubilities (1990)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 112 (1990), S. 5066-5074 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00169a011
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  • 3
    Electronic Resource
    Electronic Resource
    Ground state densities from electron propagators: Optimized Thomas–Fermi approximation for short wavelength modes (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 92 (1990), S. 6687-6696 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Electron densities obtained from a ground state path integral approach to density functional theory using a primitive Monte Carlo method display large statistical uncertainties when short wavelength fluctuations of the paths are considered directly. An optimized Thomas–Fermi approximation is developed to eliminate these degrees of freedom in a systematic and physically motivated fashion. Beyond improving the precision of the numerical results, this theoretical development permits a simple qualitative discussion of how the calculation pushes electron density into tunneling regions by iteratively renormalizing the Fermi wavelength appropriate to the remaining integrations which involve only long wavelength coordinates.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.458304
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  • 4
    Electronic Resource
    Electronic Resource
    Comparison of the structure of harmonic aqueous glasses and liquid water (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 6070-6077 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Glassy structures of water were generated by rapidly quenching configurations of 64 and 343 molecules of liquid water. The potential energy was then expanded through quadratic order around local minima generated this way and properties of the resulting harmonic system were calculated. The results were used to test the extent to which the structure of liquid water is similar to that of a harmonic aqueous glass. The radial distribution functions for the glass are remarkably similar to those of the liquid. The vibrational density of states for the glassy water exhibits a gap between 300 and 400 cm−1. The normal modes below 300 cm−1 correspond to molecular translations while the modes above 400 cm−1 are ascribed to molecular librations. Translational modes are almost entirely responsible for the broadening of oxygen–oxygen radial distribution function of the quenched configuration. They are also primarily responsible for the broadening of other radial distribution functions. Vibrational density of states leads to classical and quantum free energies for the harmonic system equal −9.62±0.12 and −8.89±0.12 kcal/mol, respectively, at T=300 K. Both free energies were found to be insensitive to sample size and to the configurational differences between the quenched structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453481
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  • 5
    Electronic Resource
    Electronic Resource
    Surface potential of the water liquid–vapor interface (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 3281-3285 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The surface potential of the water liquid–vapor interface is studied by molecular dynamics using the TIP4P model. The surface potential predicted by this empirical model is −(130±50)mV. This value for the surface potential is of reasonable magnitude but of opposite sign to the expectations derived from laboratory experiments. The electrostatic potential displays a nonmonotonic variation with depth into the liquid. This nonmonotonic variation is explained on the basis of the nondipolar charge distribution of the H2O molecule and the observation that the more probable molecular orientations in the interfacial region place the molecular symmetry axis near the plane of the interface. It is shown that minor changes in the assumed molecular charge distribution can bring the computed surface potential into agreement with experimental expectations without qualitatively altering the nonmonotonic variation of the electrostatic potential through the interfacial region. Computed quantum mechanical descriptions of the electron distribution of the isolated H2O molecule are not compatible with the surface structure predicted by the TIP4P model and the experimental expectation that the surface potential of the water liquid–vapor interface is small, roughly of the order of 10–100 mV. The surface potential is sensitive to details in the large distance wings of the molecular electron distribution. It is hypothesized that the surface environment qualitatively alters the wings of the distribution from the result obtained by a superposition of the isolated molecule electron densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453923
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  • 6
    Electronic Resource
    Electronic Resource
    Statistical theory of electron densities (1988)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 88 (1988), S. 1818-1823 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: An optimized Thomas–Fermi theory is proposed which retains the simplicity of the original theory and is a suitable reference theory for Monte Carlo density functional treatments of condensed materials. The key ingredient of the optimized theory is a neighborhood sampled potential which contains effects of the inhomogeneities in the one-electron potential. In contrast to the traditional Thomas–Fermi approach, the optimized theory predicts a finite electron density in the vicinity of a nucleus. Consideration of the example of an ideal electron gas subject to a central Coulomb field indicates that implementation of the approach is straightforward. The optimized theory is found to fail completely when a classically forbidden region is approached. However, these circumstances are not of primary interest for calculations of interatomic forces. It is shown how the energy functional of the density may be constructed by integration of a generalized Hellmann–Feynman relation. This generalized Hellmann–Feynman relation proves to be equivalent to the variational principle of density functional quantum mechanics, and, therefore, the present density theory can be viewed as a variational consequence of the constructed energy functional.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.454105
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  • 7
    Electronic Resource
    Electronic Resource
    Fluctuation method for calculation of elastic constants of solids (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 87 (1987), S. 1245-1247 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This paper derives a method for calculation of the elastic constants of a solid from computer simulation data on atomic displacement correlations at long range. It is shown that principal axes of the elastic constant tensor can be found from a Fourier analysis of the second-rank tensor of displacement correlations together with a numerical search in the reciprocal Fourier k space. The full fourth-rank tensor of elastic constants then can be obtained by rotations after the principal values are calculated. The method is not limited to special crystal symmetries, to pair-decomposable forces, to low temperatures, to thermodynamic states of only slight distortion from the minimum energy configuration, or to harmonic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.453305
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  • 8
    Electronic Resource
    Electronic Resource
    Comment on "Study on the liquid–vapor interface of water. I. Simulation results of thermodynamic properties and orientational structure'' (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 5211-5213 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: This comment on the article by Matsumoto and Kataoka [J. Chem. Phys. 88, 3233 (1988)] identifies a discrepancy between recent calculations of the surface potential of the water liquid–vapor interface. The cited work assumes that the field of a water molecule in the interfacial region is strictly the field of a point molecular dipole, whereas other works have made more detailed assumptions about the molecular charge distributions. The difference between the values for the surface potential obtained from these different assumptions is large compared to the surface potential value in question. It is shown that the numerical difference is associated with the densities of molecular quadrupole moment in the coexisting bulk phases. The correction can be evaluated analytically and applied to the molecular dynamics results after the fact.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456536
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  • 9
    Electronic Resource
    Electronic Resource
    A statistical method for identifying transition states in high dimensional problems (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 5045-5048 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A statistical method based on Monte Carlo sampling of paths associated with Markovian stochastic processes is proposed for the location of transition states in molecularly complex reactions. It is discussed in what respects the proposed method would identify transition state regions, and an algorithm for Metropolis sampling of Metropolis paths (based on the Metropolis random walk process) is devised. Physical aspects of this new algorithm are examined, and the relation of this method to simulated annealing algorithms for physical design of circuits is noted.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451695
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  • 10
    Electronic Resource
    Electronic Resource
    Discretized propagators in Hartree and Hartree–Fock theory. II. Responses to static electric and magnetic fields (1985)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 5084-5088 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Discrete propagator methods that take account of the Pauli exclusion principle through the level of many-body Hartree theory are used to investigate the linear responses of inhomogeneous electron systems to static scalar and vector potentials. The induced densities and currents are obtained in the form of configurational integrals over Bessel functions, in close analogy with classical statistical mechanical partition functions that are configurational integrals over Boltzmann weight functions. In self-consistent field treatments the arguments of these Bessel functions are themselves functionals of the electron densities in the absence of external potentials. Qualitative differences between the magnetic responses predicted by Hartree and Hartree–Fock equations are pointed out. A simplified Hartree–Fock theory for magnetic responses is also derived. Here too, the responses are shown to be configurational integrals over Bessel functions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.448630
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