Direct derivation of anisotropic atomic displacement parameters from molecular dynamics simulations demonstrated in thermoelectric materials

Atomic displacement parameters (ADPs) are crystallographic information that describe the statistical distribution of atoms around an atom site. Direct derivation of anisotropic ADPs by atom from molecular dynamics (MD) simulations, where the (co)valences of atom positions are taken over recordings at different time steps in a single MD simulation, was demonstrated on three thermoelectric materials, Ag8SnSe6, Na2In2Sn4, and BaCu1.14In0.86P2. Unlike the very frequently used lattice dynamics approach, the MD approach can obtain ADPs in disordered crystals and at finite temperature, but not under conditions where atoms migrate in the crystal. ADPs from MD simulations would act as a tool complementing experimental efforts to understand the crystal structure including the distribution of atoms around atom sites.