Nuclear quantum effects in structural and elastic properties of cubic silicon carbide

TL;DR

This study investigates the influence of nuclear quantum effects on the structural and elastic properties of cubic silicon carbide using path-integral molecular dynamics, revealing significant reductions in elastic constants and bulk modulus due to quantum vibrations.

Contribution

It introduces a path-integral molecular dynamics approach with a tight-binding Hamiltonian to quantify nuclear quantum effects in SiC, addressing a gap in conventional calculations.

Findings

Quantum effects cause up to 10% reduction in elastic constants.

Zero-point oscillations lead to 7% decrease in bulk modulus.

Quantum effects persist beyond room temperature, affecting material properties.

Abstract

Silicon carbide, a semiconducting material, has gained importance in the fields of ceramics, electronics, and renewable energy due to its remarkable hardness and resistance. In this study, we delve into the impact of nuclear quantum motion, or vibrational mode quantization, on the structural and elastic properties of 3C-SiC. This aspect, elusive in conventional {\it ab-initio} calculations, is explored through path-integral molecular dynamics (PIMD) simulations using an efficient tight-binding (TB) Hamiltonian. This investigation spans a wide range of temperatures and pressures, including tensile stress, adeptly addressing the quantization and anharmonicity inherent in solid-state vibrational modes. The accuracy of the TB model has been checked by comparison with density-functional-theory calculations at zero temperature. The magnitude of quantum effects is assessed by comparing PIMD outcomes with results obtained from classical molecular dynamics simulations. Our investigation uncovers notable reductions of 5%, 10%, and 4% in the elastic constants $C_{11}$, $C_{12}$, and $C_{44}$, respectively, attributed to atomic zero-point oscillations. Consequently, the bulk modulus and Poisson's ratio of 3C-SiC exhibit reduced values by 7% and 5% at low temperature. The persistence of these quantum effects in the material's structural and elastic attributes beyond room temperature underscores the necessity of incorporating nuclear quantum motion for an accurate description of these fundamental properties of SiC.