ZW SU

University at Buffalo, The State University of New York, Buffalo, New York, United States

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Publications (6)12.76 Total impact

  • ZW SU · P. Coppens
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    ABSTRACT: Ewald's method of accelerated convergence [Ewald (1921). Ann. Phys. (Leipzig), 64, 253-287] is generalized to calculate the electrostatic potential of a crystal in which the atoms have overlapping spherical densities, The algorithm is applied to the cubic NaF crystal. The potentials at the Na and F nuclei are calculated for the free-ion model and for the results from a kappa refinement of the experimental data of Howard and Jones [Acta Cryst, (1977), A33, 776-783]. The kappa refinement indicates an incomplete charge transfer but gives an electrostatic energy close to that of the point-charge model with full charge transfer and a lattice energy that is in good agreement with the experimental value.
    Acta Crystallographica Section A Foundations of Crystallography 01/1995; 51(1):27-32. DOI:10.1107/S0108767394004447 · 2.07 Impact Factor
  • ZW SU · P. Coppens
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    ABSTRACT: Formulae for the rotation of real spherical harmonic functions are presented. To facilitate their application, values of the matrices d m ' m (l) (π/2), which occur in the equations, are tabulated for 1≤l≤8 and 0≤m ' , m≤l. The application of the equations to spherical harmonic functions with the normalization commonly used in charge-density analysis is described.
    Acta crystallographica. Section A, Foundations of crystallography 09/1994; 50(5). DOI:10.1107/S0108767394003077 · 2.07 Impact Factor
  • ZW SU · P. Coppens
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    ABSTRACT: Normalization factors N(lj) for the Kubic harmonics K(lj) defined by [GRAPHICS] have been evaluated numerically for l less-than-or-equal-to 10.
    Acta crystallographica. Section A, Foundations of crystallography 05/1994; 50(3):408-409. DOI:10.1107/S0108767393013017 · 2.07 Impact Factor
  • ZW SU · P. Coppens
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    ABSTRACT: A method for efficiently evaluating integrals of the type AN, l1, l2, k(Z, R) = ×jl2(SR)Sk dS is discussed and closed-form expressions for those integrals useful in the calculation of the electrostatic potential, the electric field and the electric field gradient are given.
    Journal of Applied Crystallography 02/1994; 27(1):89-91. DOI:10.1107/S0021889893007009 · 3.95 Impact Factor
  • ZW SU · P Coppens
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    ABSTRACT: A method is presented to calculate the electrostatic potential, the electric field and the electric-field gradient in a crystal from the atomic multipole expansion of the experimental charge density, as described by the Hansen-Coppens formalism [Hansen & Coppens (1978), Acta Cryst. A34, 909-921]. The electrostatic properties are expressed in terms of the positions and the charge-density parameters of the individual atoms. Contributions due to the procrystal charge density and the deformation charge density are compared. The method is illustrated by the calculation of the electrostatic potential maps of fully deuterated benzene and of iron(II) tetraphenylporphyrin.
    Acta Crystallographica Section A Foundations of Crystallography 03/1992; 48 ( Pt 2):188-97. DOI:10.1107/S0108767391009820 · 2.07 Impact Factor
  • XH BU · ZW SU · P. Coppens
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    ABSTRACT: (C10H8S8)2[Cd2I6], M(r) = 1755.60, triclinic, P1BAR, a = 9.067 (2), b = 10.515 (1), c = 12.441 (2) angstrom, alpha = 97.12 (1), beta = 103.43 (1), gamma = 106.13 (1)-degrees, V = 1085 (1) angstrom 3, Z = 1, D(x) = 2.69 g cm-3, lambda-(Mo K-alpha) = 0.71073 angstrom, mu = 59.6 cm-1, F(000) = 806, room temperature, R(F) = 0.051, wR = 0.061 for 2761 unique reflections. The structure consists of pairs of BEDT-TTF cations [BEDT-TTF = bis(ethylenedithio)tetra-thiafulvalene] with an interplanar separation of 3.53 angstrom and Cd2I62- anions formed by two CdI42- tetrahedra sharing one common edge. pi-pi molecular overlap exists within each pair of BEDT-TTF molecules, while different pairs are linked via S...S contacts, which are as short as 3.339 (3) angstrom.
    Acta Crystallographica Section C Crystal Structure Communications 02/1991; 47(2):279-282. DOI:10.1107/S0108270190008071 · 0.54 Impact Factor