TY - JOUR
T1 - Influence of intermolecular interactions on multipole-refined electron densities
AU - Spackman, MA
AU - Byrom, PG
AU - Alfredsson, M
AU - Hermansson, K
PY - 1999/1
Y1 - 1999/1
N2 - This work examines the effect of intermolecular interactions on molecular properties derived from simulated X-ray diffraction data. Model X-ray data are computed from a superposition of ab initio molecular electron densities in the crystal, as well as from periodic crystal Hartree-Fock electron densities, for the hydrogen-bonded systems ice VIII, formamide and urea, as well as the weakly bound acetylene. The effects of intermolecular interactions on the electron density are illustrated at both infinite and finite data resolution, and it is concluded that multipole models are capable of quantitative retrieval of the interaction density, despite the known shortcomings of the radial functions in the model. Multipole refinement reveals considerable enhancement of the molecular dipole moment for hydrogen-bonded crystals, and negligible change in molecular second moments. Electric field gradients at H nuclei are significantly reduced in magnitude upon hydrogen bonding, and this change is also faithfully represented by the rigid pseudoatom model.
AB - This work examines the effect of intermolecular interactions on molecular properties derived from simulated X-ray diffraction data. Model X-ray data are computed from a superposition of ab initio molecular electron densities in the crystal, as well as from periodic crystal Hartree-Fock electron densities, for the hydrogen-bonded systems ice VIII, formamide and urea, as well as the weakly bound acetylene. The effects of intermolecular interactions on the electron density are illustrated at both infinite and finite data resolution, and it is concluded that multipole models are capable of quantitative retrieval of the interaction density, despite the known shortcomings of the radial functions in the model. Multipole refinement reveals considerable enhancement of the molecular dipole moment for hydrogen-bonded crystals, and negligible change in molecular second moments. Electric field gradients at H nuclei are significantly reduced in magnitude upon hydrogen bonding, and this change is also faithfully represented by the rigid pseudoatom model.
KW - QUADRUPOLE COUPLING-CONSTANTS
KW - PERIODIC HARTREE-FOCK
KW - DYNAMIC STRUCTURE FACTORS
KW - AB-INITIO CALCULATIONS
KW - OXALIC-ACID DIHYDRATE
KW - RAY-DIFFRACTION DATA
KW - FIELD GRADIENTS
KW - NEUTRON-DIFFRACTION
KW - LIQUID WATER
KW - MOLECULAR-CRYSTALS
U2 - 10.1107/S0108767398007181
DO - 10.1107/S0108767398007181
M3 - Article
SN - 0108-7673
VL - 55
SP - 30
EP - 47
JO - Acta Crystallographica Section A
JF - Acta Crystallographica Section A
ER -