
[Show abstract] [Hide abstract]
ABSTRACT: Ewald's method of accelerated convergence [Ewald (1921). Ann. Phys. (Leipzig), 64, 253287] 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 freeion model and for the results from a kappa refinement of the experimental data of Howard and Jones [Acta Cryst, (1977), A33, 776783]. The kappa refinement indicates an incomplete charge transfer but gives an electrostatic energy close to that of the pointcharge model with full charge transfer and a lattice energy that is in good agreement with the experimental value. No preview · Article · Jan 1995 · Acta Crystallographica Section A Foundations of Crystallography

[Show abstract] [Hide abstract]
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 chargedensity analysis is described. No preview · Article · Sep 1994 · Acta crystallographica. Section A, Foundations of crystallography

[Show abstract] [Hide abstract]
ABSTRACT: Normalization factors N(lj) for the Kubic harmonics K(lj) defined by [GRAPHICS] have been evaluated numerically for l lessthanorequalto 10. No preview · Article · May 1994 · Acta crystallographica. Section A, Foundations of crystallography

[Show abstract] [Hide abstract]
ABSTRACT: A method for efficiently evaluating integrals of the type AN, l1, l2, k(Z, R) = ×jl2(SR)Sk dS is discussed and closedform expressions for those integrals useful in the calculation of the electrostatic potential, the electric field and the electric field gradient are given. No preview · Article · Feb 1994 · Journal of Applied Crystallography

[Show abstract] [Hide abstract]
ABSTRACT: A method is presented to calculate the electrostatic potential, the electric field and the electricfield gradient in a crystal from the atomic multipole expansion of the experimental charge density, as described by the HansenCoppens formalism [Hansen & Coppens (1978), Acta Cryst. A34, 909921]. The electrostatic properties are expressed in terms of the positions and the chargedensity 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. No preview · Article · Mar 1992 · Acta Crystallographica Section A Foundations of Crystallography

[Show abstract] [Hide abstract]
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 cm3, lambda(Mo Kalpha) = 0.71073 angstrom, mu = 59.6 cm1, F(000) = 806, room temperature, R(F) = 0.051, wR = 0.061 for 2761 unique reflections. The structure consists of pairs of BEDTTTF cations [BEDTTTF = bis(ethylenedithio)tetrathiafulvalene] with an interplanar separation of 3.53 angstrom and Cd2I62 anions formed by two CdI42 tetrahedra sharing one common edge. pipi molecular overlap exists within each pair of BEDTTTF molecules, while different pairs are linked via S...S contacts, which are as short as 3.339 (3) angstrom. No preview · Article · Feb 1991 · Acta Crystallographica Section C Crystal Structure Communications