First principle based phase stability in PMN-xPT

TL;DR

This study uses a first-principles based shell model to analyze phase stability in PMN-xPT, revealing three distinct regions with different symmetries and behaviors depending on Ti content, aligning with experimental observations.

Contribution

It introduces a first-principles fitted shell model to predict phase stability and symmetry changes in PMN-xPT across different compositions.

Findings

Identifies three compositional regions with distinct symmetries

Shows low Ti region is rhombohedral with disorder

High Ti region exhibits tetragonal ferroelectric behavior

Abstract

We have applied a shell model potential developed by fitting first principle results to describe the behavior of the relaxor-ferroelectric PMN-xPT as function of concentration. The solid solution exhibits three regions with different characteristics according to Ti content in agreement with the experiments. At low Ti the polar and structural disorder dominates, and the symmetry is rhombohedral. The intermediate region is ferroelectric with easy rotation of the polarization direction, and the symmetry appears orthorhombic. Finally, in the high Ti content region, the solid solution adopts a ferroelectric behavior similar to PT, with tetragonal symmetry.