Neutron diffraction study of amorphous (As0.5Te0.5)1-xIx system

Neutron and X-ray diffraction measurements have been carried out on amorphous (As0.5Te0.5)1-xIx alloys with x=0 - 0.2 to elucidate details of structural and bonding features in the amorphous As-chalcohalide system. The first sharp diffraction peak is clearly found at around Q = 1.2 A-1 in the structure factor of the neutron diffraction measurement. The position of the first peak at γ=2.57 A in the pair distribution function of amorphous As0.5 Te0.5 shifts to a larger γ side with increasing x. Interatomic distances in the first coordination shell. γAs-As, γAs-Te and γTe-1, determined by the least squares fitting analysis to the observed structure factor, are 2.51, 2.64 and 2.75 A, respectively, which are in good agreement with those reported in our previous EXAFS study. It has become apparent by the present result that I atoms in the system are preferentially bonded to Te atoms in the AsTe3/2-unit network structure. (author)