The temperature dependence of high order static elastic module near the structure phase transition

Abstract

In the frame of Landau theory the temperature dependence of the third and the fourth elastic module near the structure phase transition is considered. The general expressions are obtained by taking into account linear and square connection of strain u and the order parameter η. The calculations were performed for the scalar thermodynamic potential. In some particular cases the critical temperature behaviour of the high order elastic module were presented in an evident form. The calculations have been compared with experimental results for proper ferroelectrics and ferroelastics.

Keywords:

• Phase transition
• high order elastic module
• Landau theory
• critical index