Open AccessX‐ray charge density study of p ‐amino‐ p ′‐nitrobiphenyl at 20 K using a CCD area detector and synchrotron radiation: a very large dipole moment enhancement in the solid state
Author(s) -
Wu Guang,
Volkov Anatoliy,
Coppens Philip
Publication year - 1999
Publication title -
journal of synchrotron radiation
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.172
H-Index - 99
ISSN - 1600-5775
DOI - 10.1107/s0909049599005166
Subject(s) - beamline , synchrotron radiation , synchrotron , dipole , cryostat , detector , chemistry , physics , atomic physics , optics , beam (structure) , condensed matter physics , superconductivity , organic chemistry
Accurate 20 K intensity data were collected on a crystal of p ‐amino‐ p ′‐nitrobiphenyl [ a = 24.348(1), b = 5.802 (1), c = 7.158 (1) Å, α = β = γ = 90°, space group Pca 2 1 ] at the SUNY X3A1 beamline at the National Synchrotron Light Source, using a CCD area detector and a DISPLEX cryostat. The sharp vertical profile of the synchrotron beam, combined with a slight instability of the cryostat, necessitates a ϕ‐dependent correction, made possible by a large redundancy in the data set, the average multiplicity of the measurements being 8.02. In the multipole refinement, net atomic charges were constrained to those from a κ‐refinement, corresponding to a more local definition of the pseudoatoms in the crystal. Both localized and unrestricted refinements show a very large (more than threefold) enhancement of the dipole moment in the solid state compared with that of the isolated molecule.