Boundary Condition Effect in MD Simulation: A Case of the α→β Phase Transition in Superionic Conductor Ag2Se

The low temperature phase transition in Ag 2 Se is investigated for various sizes of the system by means of a molecular dynamics simulation. It is confirmed that the correct structure of the low temperature phase is orthorhombic and belongs to Pmnb space group. In order to transform successfully to the low temperature phase, it is necessary that more than one MD cell vector is composed of even number times bcc unit cell vector in the superionic phase.