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  • 1
    Electronic Resource
    Electronic Resource
    Quantum mechanical geometry optimization in solution using a finite element continuum electrostatics method (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 5472-5484 
    Details
    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
    URL: http://dx.doi.org/10.1063/1.472388
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    Paper (German National Licenses)
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  • 2
    Electronic Resource
    Electronic Resource
    Pseudospectral localized Møller–Plesset methods: Theory and calculation of conformational energies (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 103 (1995), S. 1481-1490 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have developed an algorithm based upon pseudospectral ab initio electronic structure methods for evaluating correlation energies via the localized Møller–Plesset methodology of Pulay and Saebo. Even for small molecules (∼20 atoms) CPU times are diminished by a factor of ∼10 compared to canonical MP2 timings for Gaussian 92 and the scaling is reduced from N4−N5 in conventional methods to ∼N3. We have tested the accuracy of the method by calculating conformational energy differences for 36 small molecules for which experimental data exists, using the Dunning cc-pVTZ correlation consistent basis set. After removing 6 test cases on the grounds of unreliability of the experimental data, an average deviation with experiment of 0.18 kcal/mol between theory and experiment is obtained, with a maximum deviation of ∼0.55 kcal/mol. This performance is significantly better than that obtained previously with a smaller basis set via canonical MP2; it is also superior to the results of gradient corrected density functional theory. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.469769
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  • 3
    Electronic Resource
    Electronic Resource
    Parallel pseudospectral electronic structure: I. Hartree-Fock calculations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1017-1029 
    Details
    ISSN: 0192-8651
    Keywords: pseudospectral ; parallel ; Hartree-Fock ; gradient ; scalable ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We present an outline of the parallel implementation of our pseudospectral electronic structure program, Jaguar, including the algorithm and timings for the Hartree-Fock and analytic gradient portions of the program. We also present the parallel algorithm and timings for our Lanczos eigenvector refinement code and demonstrate that its performance is superior to the ScaLAPACK diagonalization routines. The overall efficiency of our code increases as the size of the calculation is increased, demonstrating actual as well as theoretical scalability. For our largest test system, alanine pentapeptide [818 basis functions in the cc-pVTZ(-f) basis set], our Fock matrix assembly procedure has an efficiency of nearly 90% on a 16-processor SP2 partition. The SCF portion for this case (including eigenvector refinement) has an overall efficiency of 87% on a partition of 8 processors and 74% on a partition of 16 processors. Finally, our parallel gradient calculations have a parallel efficiency of 84% on 8 processors for porphine (430 basis functions).   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1017-1029, 1998
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 4
    Electronic Resource
    Electronic Resource
    Parallel pseudospectral electronic structure: II. Localized Møller-Plesset calculations (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Computational Chemistry 19 (1998), S. 1030-1038 
    Details
    ISSN: 0192-8651
    Keywords: pseudospectral ; parallel ; localized Møller-Plesset, scalable ; Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Computer Science
    Notes: We have developed a parallel version of our pseudospectral localized Møller-Plesset electronic structure code. We present timings for molecules up to 1010 basis functions and parallel speedup for molecules in the range of 260-658 basis functions. We demonstrate that the code is scalable; that is, a larger number of nodes can be efficiently utilized as the size of the molecule increases. By taking advantage of the available distributed memory and disk space of a scalable parallel computer, the parallel code can calculate LMP2 energies of molecules too large to be done on workstations.   © 1998 John Wiley & Sons, Inc.   J Comput Chem 19: 1030-1038, 1998
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
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