A first-principles study of structural and elastic properties of bulk SrRuO$_3$

TL;DR

This study uses density functional theory to analyze the structural and elastic properties of bulk SrRuO$_3$ in various phases, revealing phase transitions and stability issues related to shear deformation.

Contribution

It provides a comprehensive first-principles analysis of SrRuO$_3$'s structural and elastic properties, including phase stability and deformation behavior, which was previously lacking.

Findings

Identification of DFT approaches best matching experimental lattice constants

Discovery of a shear-induced isosymmetric phase transition in orthorhombic SrRuO$_3$

Observation of mechanical instability in tetragonal SrRuO$_3$ under shear deformation

Abstract

We present a first-principles investigation of structural and elastic properties of experimentally observed phases of bulk SrRuO$_3$ - namely orthorhombic, tetragonal, and cubic - by applying density functional theory (DFT) approximations. At first, we focus our attention on the accuracy of calculated lattice constants in order to find out DFT approaches that best represent the crystalline structure of SrRuO$_3$, since many important physical quantities crucially depend on change in volume. Next, we evaluate single-crystal elastic constants, mechanical stability, and macroscopic elastic parameters trying to at least partially compensate for the existing lack of information about these fundamental features of SrRuO$_3$. Finally, we analyze the anomalous behavior of low-temperature orthorhombic phase under $C_{44}$ related shear deformation. It turns out that at critical strain values the system exhibits a distinct deviation from the initial behavior which results in an isosymmetric phase transition. Moreover, under $C_{44}$ related shear deformation tetragonal SrRuO3 becomes mechanically unstable raising an open question of what makes it experimentally observable at high temperatures.