IFIS - LITORAL   24734
INSTITUTO DE FISICA DEL LITORAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Development of an atomic level model of BiFeO3 from first-principles
Autor/es:
M. GRAF; M. SEPLIARSKY; M. G. STACHIOTTI; S. TINTE
Lugar:
Cracovia
Reunión:
Congreso; 13th INTERNATIONAL MEETING ON FERROELECTRICITY; 2013
Institución organizadora:
The August Chełkowski Institute of Physics, The Department of Ferroelectrics Physics, University of Silesia, Katowice, Poland & The Institute of Physics, Jagiellonian University, Krak√≥w, Poland & Polish Physical Society
Resumen:
We develop a first-principles atomistic shell model for BiFeO3 to study its ferroelectric and structural properties as a function of temperature. The parameters of our atomistic potential are adjusted to reproduce values of energies, forces and stresses obtained with first-principles calculations in different relevant configurations. The resulting model is then used to carry out molecular dynamics simulations at finite temperature in systems of 12x12x12 5-atom unit cells with periodic boundary conditions. The simulations show that at low temperature the model reproduces the ground-state ferroelectric structure with R3c symmetry, describing the equivalent pseudocubic lattice parameters, a net polarization along [111] direction and oxygen octahedron tilting of a-a-a- in Glazer notation. This rhombohedral R3c phase remains stable up to 750 K, where a clear first-order transition to a paraelectric Pnma symmetry phase takes place. Specifically, at this temperature there is a discontinuous reduction of the lattice parameters, the macroscopic polarization vanishes and the oxygen octahedral tilting becomes a-a-b+. Our results indicate that the developed model captures the delicate structural behavior showed by ab-initio calculations, and remarkably is able to reproduce satisfactorily the temperature behavior observed in experiments.
rds']