Mechanical, thermal and optical properties of perovskite borides RRh3B(R = Y, Zr, and Nb)

TL;DR

This study uses ab initio DFT calculations to explore the structural, elastic, thermodynamic, and optical properties of RRh3B perovskite borides, revealing their ductility, anisotropy, and high reflectivity, with implications for coating applications.

Contribution

First comprehensive analysis of thermodynamic and optical properties of RRh3B compounds using DFT and quasi-harmonic Debye model, including temperature and pressure dependence.

Findings

Materials are more ductile than MAX phases.

Strong anisotropy observed, especially in NbRh3B.

High reflectivity in IR-UV spectrum up to ~20 eV.

Abstract

We report here ab initio density functional theory (DFT) calculations of structural, elastic, Peierls stress, thermodynamic and optical properties of RRh3B (R = Y, Zr and Nb) using the plane wave psedudopotential method. The materials possess better ductile behavior in comparison with a selection of layered MAX phases but the anisotropy is strong, particularly in NbRh3B. The Peierls stress, approximately 3-4 times larger than in MAX phases, show that dislocation movement may follow but with much reduced occurrences compared to MAX phases. The temperature and pressure dependence of bulk modulus, specific heats, thermal expansion coefficient, and Debye temperature are calculated for the first time for two of the three compounds using the quasi-harmonic Debye model with phononic effects for elevated temperature and pressure. The obtained results are discussed in comparison to the behavior of other related compounds. Further the features of optical functions obtained for the first time are discussed. The study reveals that the reflectivity is high in the IR-UV regions up to ~ 17.5 eV (YRh3B, ZrRh3B) and 20 eV (NbRh3B), thus showing promise as good coating materials. Keywords: RRh3B; Quasi-harmonic Debye model; Thermodynamic properties; Optical properties