Open Access

ABSTRACT

The structure of BaZrO$_3$: a comparative first-principles study

by ,

1 e-mail: bilica@ihpc.a-star.edu.sg. Materials Theory and Simulation Laboratory, Institute of High Performance Computing, 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632

The International Conference on Computational & Experimental Engineering and Sciences 2009, 13(1), 13-14. https://doi.org/10.3970/icces.2009.013.013

Abstract

Using several popular first-principles packages for materials modeling the nature of the cubic lattice of barium zirconate has been investigated. The evaluated vibrational spectra typically exhibit an extended and prominent dynamical instability. The instability manifests through imaginary frequency optical modes along the whole R-M edge of the Brillouin zone. The experimentally observed simple cubic structure is found to be dynamically unstable against an antiferro-distortive transformation. The computations predict an orthorhombic crystal structure of the material, only slightly distorted from the cubic lattice, with an eight times larger unit cell and alternate ZrO₆ octahedra slightly rotated in opposite directions around the cartesian axes. The neglect of the barium 5s² and 5p⁶ electrons in the valence configuration of Ba is found to be responsible for the previously reported incorrect results. Possible reasons for the observations of a stable cubic structure are discussed as well as the implications for the previously reported results. The ways to recover correct results from several previous studies that predicted the cubic structural model of BaZrO3 and to avoid potential pitfalls in the future are suggested.

---