Firs-principles based atomistic modeling of BiFeO3

M. GRAF; M. SEPLIARSKY; M. G. STACHIOTTI; S. TINTE

Montevideo

Workshop; V Workshop on Novel Methods for Electronic Structure Calculations.; 2013

p { margin-bottom: 0cm; direction: ltr; color: rgb(0, 0, 0); text-align: justify; widows: 2; orphans: 2; }p.western { font-family: "Times New Roman",serif; font-size: 12pt; }p.cjk { font-family: "Times New Roman",serif; font-size: 12pt; }p.ctl { font-family: "Times New Roman",serif; font-size: 10pt; }a:visited { color: rgb(128, 0, 128); }a.western:visited { }a.cjk:visited { }a.ctl:visited { }a:link { color: rgb(0, 0, 255); } The combination of first-principles calculations with classical atomic models is a powerful approach to the investigation of systems where a large number of atoms are involved, to the study of compositional effects in solid solutions, and to the computation of finite temperature properties in oxide materials. Among these methods, molecular dynamics simulations with atomic level models fitted to first-principles calculations have been shown to be very successful for predicting the qualitative behavior of pure compounds and solid solutions. In this work we apply a shell model description in order to study the structural and ferroelectric properties of the multiferroic perovskite BiFeO3 as a function of temperature and under the effects of an external electric field. The developed model is able to capture the delicate structural behavior showed by first-principlescalculations, and it reproduces satisfactorily the temperature behavior observed in experiments. The simulations show that the rhombohedral ground state of R3c symmetry remains stable up to TC = 1100 K. At this temperature a strong first order transition to an orthorhombic phase of Pbnm symmetry takes place. A detailed analysis of the structure and the behavior of the system under an electric field indicate the antiferroelectric nature of this high temperature phase.