Ferroelectric transitions, molecular dynamics and intrinsic surface problems

Conventional supercell molecular dynamics, if applied to a system where one has reasonable potentials and which is known experimentally to have a ferroelectric ground state, can fail to reproduce that state. We shall show that such behavior stems from a failure, intrinsic in this type of molecular dynamics, to handle the surface effects intrinsic to Coulomb interactions. We will discuss how this limitation can be addressed and its possible implication for ground state energies calculated by using periodic boundary conditions.