Green's function theory of phase transition in squaric acid (H₂C₄O₄) crystal

Abstract

The Green's function method with the symmetry decoupling scheme has been used in the present paper to investigate the antiferroelectric phase transition in squaric acid (H₂C₄O₄) crystal. It is shown that the phase transition is of first order. The transition temperature T_c and the order parameter S_c at transition point are obtained. The dispersion relation, internal energy and transition entropy are derived respectively. Theoretical results are in agreement with those of recent experiments.