On the role of Al-Si ordering in the cubic-tetragonal phase transition of leucite

Abstract

The cubic-tetragonal phase transition in leucite has been examined using static lattice energy calculations with realistic, tested interatomic potentials. The calculations have demonstr~ted that the ~ransitio~ is not triggered by AI-Si ordering and can occur without any ordenng. Any AI-Sl order w1l1have only a minor effect on the observed spontaneous strain and structure distortion. Calculations show that any long-range AI-Si order is associated with the energetics of next-nearest AI-O-AI linkages rather than nearest neighbor interactions, leading to a low ordering temperature.