Ab initio molecular dynamics simulations of structural change in liquid Se30Te70 from low- to high-density phases

The temperature dependence of atomic and electronic structures in liquid Se30Te70 is studied using ab initio molecular dynamics simulations. Our work verifies the structural change from low- to high-density phases observed in experiments. Moreover, we show that the structure of low-density liquid is an open twofold coordinated chain structure, which can be discussed by Peierls distorted local structures around both Se and Te atoms, and that of high-density liquid is a denser threefold coordinated structure. The structural change is due to the increasing interchain charge transfer with increasing temperature, which causes the breakup of Peierls distorted local structure. Our work also presents that a higher temperature is needed to destroy the Peierls distorted local structures around Se atoms than that around Te atoms. Thus, with increasing Se concentration in liquid SexTe1-x, the percent of Peierls distorted local structures around Se atoms gradually increases and the structural change moves toward higher temperature. These results suggest that the collapse of the open atomic configuration plays an important role in the structural change in liquid Se-Te alloy, which shows a rough resemblance to that in liquid P and supercooled H2O.