Neutron-Diffraction Studies of Network Structure in Amorphous Phosphorus

Neutron diffraction studies have been made for three samples of amorphous phosphorus. The structure factor data have been transformed to give the real-space correlation function, d(r). All samples were found to contain a small proportion of hydrogen and corrections were made before the data was analysed. The violet form was found to give a typical amorphous pattern which had a sharp main diffraction peak at 1.1 angstrom-1. On heat-treating the sample, this peak increased in intensity but the rest of the pattern was unaltered. The red-brown form exhibited some Bragg peaks, but the overall shape of the pattern was similar to that of the violet material. The d(r) function exhibits a sharp peak at 2.21 angstrom corresponding to the PP-bondlength and a second peak at 3.45 angstrom defining a mean bond-angle of 102.6-degrees with a spread of 4-degrees. At higher values there is a distinct three-peak characteristic which is not reproduced in current models based on a three-bonded CRN scheme.