Self-consistent approximation schemes for the treatment of a prototype ferroelectric

Abstract

Abstract As a simple prototype of a ferroelectric crystal we treat a system of coupled anharmonic oscillators in order to determine the range of applicability of different self-consistent approximation schemes. In particular, we examine the self-consistent phonon approximation with an intercell coupling which possesses a variable range of interaction. In the limit where the interaction is of sufficiently long range, the density matrix of the system is obtained numerically exactly.