Path-integral molecular dynamics simulation of 3C-SiC

TL;DR

This study uses path-integral molecular dynamics with quantum mechanical treatment of electrons and nuclei to simulate 3C-SiC, accurately reproducing experimental thermal expansion, bulk modulus, and electronic gap behavior, highlighting nuclear quantum effects at low temperatures.

Contribution

It introduces a quantum mechanical simulation approach combining tight-binding and path integral methods for 3C-SiC, assessing nuclear quantum effects on its properties.

Findings

Realistic reproduction of thermal expansion and bulk modulus.

Good agreement of electronic gap with experimental data.

Quantum effects on nuclei are significant below 250 K.

Abstract

Molecular dynamics simulations of 3C-SiC have been performed as a function of pressure and temperature. These simulations treat both electrons and atomic nuclei by quantum mechanical methods. While the electronic structure of the solid is described by an efficient tight-binding Hamiltonian, the nuclei dynamics is treated by the path integral formulation of statistical mechanics. To assess the relevance of nuclear quantum effects, the results of quantum simulations are compared to others where either the Si nuclei, the C nuclei or both atomic nuclei are treated as classical particles. We find that the experimental thermal expansion of 3C-SiC is realistically reproduced by our simulations. The calculated bulk modulus of 3C-SiC and its pressure derivative at room temperature show also good agreement with the available experimental data. The effect of the electron-phonon interaction on the direct electronic gap of 3C-SiC has been calculated as a function of temperature and related to results obtained for bulk diamond and Si. Comparison to available experimental data shows satisfactory agreement, although we observe that the employed tight-binding model tends to overestimate the magnitude of the electron-phonon interaction. The effect of treating the atomic nuclei as classical particles on the direct gap of 3C-SiC has been assessed. We find that non-linear quantum effects related to the atomic masses are particularly relevant at temperatures below 250 K.