Neutron diffraction of liquid arsenic-tellurium mixtures near the semiconductor-metal transition

Neutron scattering measurements have been carried out for liquid As-Te mixtures containing 10, 20 and 30 at.% As in the temperature range between 400 and 600 °C. The local structure was analyzed by combining the information available from our previous EXAFS results. The partial coordination number for As-Te, n_As-Te, for the mixture containing 20 at.% As decreases from 3.0-2.5 at 400 °C to 2.0-1.7 at 600 °C, suggesting that a 'network-chain' structural transformation occurs on the semiconductor to metal transition at high temperature. We propose that the first sharp diffraction peak observed around 1.4 Å^-1 in S(Q) indicates the presence of small chain clusters. It is found that the position of the second peak of g(r) shifts to smaller r at high temperature, which leads to volume contraction.