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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 5472-5484 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present a new algorithm for performing ab initio solution phase geometry optimizations. The procedure is based on the self consistent-reaction-field method developed in our laboratory which combines electronic structure calculations with a finite element formulation of the continuum electrostatics problem. A gradient for the total solution phase free energy is obtained by combining different contributions from the gradient of the classical polarization free energy and the derivatives of the quantum mechanical energy. The method used in obtaining the classical gradient is based on exact linear algebra relations and a Green function formalism due to Handy and Schaefer. Both the classical and quantum mechanical gradients are validated by comparison with energy finite differences. The result of applications to a number of small organic compounds are discussed. Comparisons between the predicted location and depth of the various solution phase minima of the Ramachandran map for the alanine dipeptide and those reported by Gould et al. are also presented. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 107 (1997), S. 6400-6414 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The derivation of a three-dimensional integral equation for solute molecule-solvent site correlation functions is presented. The equation is obtained by averaging the Ornstein–Zernicke equation for molecular liquids over orientations of the solvent molecule consistent with one site of the solvent remaining at a fixed distance from a solute-based origin. The approach is similar to that adopted in the reduction leading to the reference interaction site model (RISM) equations but retains full three-dimensional information regarding the structure of the reference solute molecule. The proposed equation can be solved using three-dimensional HNC-like closures, of which three different forms are discussed. A formulation which allows the introduction of long range interactions through a renormalization of the equation is also presented. Applications to various molecular liquids indicate that the proposed theory provides pair correlation functions that are in better agreement with molecular dynamics simulations than those obtained using the extended RISM formulation. Furthermore, qualitative errors in the correlation functions, frequently seen in results from RISM calculations are completely eliminated through geometrical averaging of the Mayer function in the 3D HNC closure. Prospects for the development of a novel mean field theory of solvation are also discussed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 1591-1608 
    ISSN: 0192-8651
    Keywords: dielectric continuum ; Poisson-Boltzmann equation ; finite element ; electrostatics ; solvation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: The automatic three-dimensional mesh generation system for molecular geometries developed in our laboratory is used to solve the Poisson-Boltzmann equation numerically using a finite element method. For a number of different systems, the results are found to be in good agreement with those obtained in finite difference calculations using the DelPhi program as well as with those from boundary element calculations using our triangulated molecular surface. The overall scaling of the method is found to be approximately linear in the number of atoms in the system. The finite element mesh structure can be exploited to compute the gradient of the polarization energy in 10-20% of the time required to solve the equation itself. The resulting timings for the larger systems considered indicate that energies and gradients can be obtained in about half the time required for a finite difference solution to the equation. The development of a multilevel version of the algorithm as well as future applications to structure optimization using molecular mechanics force fields are also discussed.   © 1997 John Wiley & Sons, Inc.   J Comput Chem 18: 1591-1608, 1997
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 18 (1997), S. 1570-1590 
    ISSN: 0192-8651
    Keywords: dielectric continuum ; Poisson-Boltzmann equation ; finite element ; mesh generation ; grid generation ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We present an automatic three-dimensional mesh generation system for the solution of the Poisson-Boltzmann equation using a finite element discretization. The different algorithms presented allow the construction of a tetrahedral mesh using a predetermined spatial distribution of vertices adapted to the geometry of the dielectric continuum solvent model. A constrained mesh generation strategy, based on Bowyer's algorithm, is used to construct the tetrahedral elements incrementally and embed the Richards surface of the molecule into the mesh as a set of triangular faces. A direct mesh construction algorithm is then used to refine the existing mesh in the neighborhood of the dielectric interface. This will allow an accurate calculation of the induced polarization charge to be carried out while maintaining a sparse grid structure in the rest of the computational space. The inclusion of an ionic boundary at some finite distance from the dielectric interface can be automatically achieved as the grid point distribution outside the solute molecule is constructed using a set of surfaces topologically equivalent to this boundary. The meshes obtained by applying the algorithm to real molecular geometries are described.   © 1997 John Wiley & Sons, Inc.   J Comput Chem 18: 1570-1590, 1997
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Publication Date: 1996-10-01
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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  • 6
    Publication Date: 1997-10-22
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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  • 7
    Publication Date: 1997-02-08
    Print ISSN: 0021-9606
    Electronic ISSN: 1089-7690
    Topics: Chemistry and Pharmacology , Physics
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