Electron Density Study of a New Non-linear Optical Material: L-Arginine Phosphate Mono-hydrate (LAP). Comparison Between X-X and X-(X + N) Refinements

摘要

The crystal structure, thermal vibrations and electron density of L-arginine phosphate monohydrate (formally C_6H_(15)N_4O_2~+.H_2PO_4~-.H_2O) have been analysed using 130 K single-crystal X-ray diffraction data to a resolution of (sin#/A)max = 1.20A~'. A multipolar pseudo-atom density model was fitted against the 6805 observed data with I > 3a(I), [R(F) = Q.O16,RW(F) = 0.014,5 = 1.39] in order to map the static valence-electron density distribution. Positional and thermal vibration parameters for H atoms were taken from neutron diffraction results. A comparison between the electron density p(r), V2p(r) and the electrostatic potential calculated from X-X and X-(X + N) refinements shows that reliable results may be obtained from X-X data only.