The crystal structure of γ-P4, one of three modifications hitherto reported on white phosphorus was determined from X-ray powder diffraction data collected atT=123 K on a Guinier-Simon camera equipped with a cold gas blower and an image plate detector. The crystal structure of γ-P4was solved by the method of simulated annealing, and the subsequent Rietveld refinement in the range 12°<2θ<92°employing rigid-body constraints on the P4molecule converged atRp=3.8%, wRp=5.0%, andRF2=14.0%. The asymmetric unit of γ-P4contains three P atoms; two P atoms in a molecule are related by a mirror plane which bisects the molecule. The centers of gravity of these P4molecules show a distorted body-centered cubic (bcc) arrangement. The four apices of the P4tetrahedron point to the largest possible voids formed by neighbor molecules. The difference to the crystal structure of SiF4and GeF4with an exact bcc arrangement of tetrahedral molecules is discussed as well as, in terms of layer stackings, the similarity of the structures of γ- and β-P4.
