Brillouin scattering and molecular dynamics study of the elastic properties of Pb(Mg1/3Nb2/3)O3

TL;DR

This study combines Brillouin spectroscopy and molecular dynamics simulations to determine the elastic properties of Pb(Mg1/3Nb2/3)O3, revealing its elastic constants, bulk modulus, optical isotropy, and anisotropy, and comparing different models.

Contribution

It provides comprehensive elastic constants and bulk modulus for PMN using experimental and simulation methods, highlighting the effects of chemical ordering and model differences.

Findings

Brillouin spectroscopy yields a bulk modulus of 103 GPa.

MD simulations overestimate elastic constants but match anisotropy.

PMN is optically isotropic with a refractive index of 2.52.

Abstract

We report the complete set of elastic constants and the bulk modulus for single crystal Pb(Mg1/3Nb2/3)O3 (PMN) at room temperature obtained from Brillouin spectroscopy and molecular dynamics (MD) simulations. The bulk modulus from Brillouin is found to be 103 GPa, in a good agreement with earlier x-ray studies. We also derived the refractive index along all principal axes and found PMN to be optically isotropic, with a refractive index of 2.52 +/- 0.02. PMN shows mechanical anisotropy with A=1.7. The MD simulations of PMN using the random site model overestimate the elastic constants by 20-50 GPa and the bulk modulus is 148 GPa, but the mechanical anisotropy matches the Brillouin results of A = 1.7. We also determined the elastic constants for various models of PMN and we find variation in the elastic constants based on chemical ordering.