SHORT-RANGE STRUCTURE OF AS-S-I SYSTEM

Time-of-flight neutron diffraction and Raman scattering measurements have been carried out for amorphous and partly liquid (As2S3)1-x(AsI3)s in order to investigate the modification of the AsS3/2 network structure by adding iodine atoms. The distribution function for all compositions shows two peaks at 2.27 and 2.62 angstrom in the first-neighbor shell, which correspond to the As-S correlation in AsS3/2 structural units and the As-I correlation in ASI3 Molecules, respectively. The Raman spectrum in the system exhibits two significant components, one of which is considerably broadened and is ascribed to the As-S vibrational mode in ASS3/2 units, and the other is well defined and is ascribed to the As-I stretching and bending modes in AsI3 Molecules. The presence of a prepeak in the neutron intensity curves and the broadened bandshape of the Raman spectrum for AsS3/2 units suggest that the connection of this unit is kept over a wide composition range in the system.