Quantum nuclear motion in silicene: Assessing structural and vibrational properties through path-integral simulations

TL;DR

This study uses path-integral simulations to analyze how quantum nuclear motion affects the structural and vibrational properties of silicene across a wide temperature range, highlighting significant deviations from classical predictions.

Contribution

It provides the first detailed quantum simulation analysis of silicene's structural and vibrational properties, emphasizing the importance of quantum effects in 2D materials.

Findings

Quantum delocalization significantly alters silicene's structural parameters.

Quantum effects cause a 14% decrease in the 2D compression modulus at low temperatures.

Quantum nuclear fluctuations influence thermal expansion and phonon spectra.

Abstract

This paper explores the interplay between quantum nuclear motion and anharmonicity, which causes nontrivial effects on the structural and dynamical characteristics of silicene, a two-dimensional (2D) allotrope of silicon with interesting electronic and mechanical properties. Employing path-integral molecular dynamics (PIMD) simulations, we investigate the quantum delocalization of nuclei, unraveling its impact on the behavior of silicene at the atomic scale. Our study reveals that this delocalization induces significant deviations in the structural parameters of silicene, influencing in-plane surface area, bond lengths, angles, compressibility, and overall lattice dynamics. Through extensive simulations, we delve into the temperature-dependent behavior between 25 and 1200 K, unveiling the role of quantum nuclear fluctuations in dictating thermal expansion and phonon spectra. The extent of nuclear quantum effects is assessed by comparing results of PIMD simulations using an efficient tight-binding Hamiltonian, with those obtained from classical molecular dynamics simulations. We compare the magnitude of quantum effects in this material with those in other related 2D crystalline solids, such as graphene and SiC monolayers. The observed quantum effects showcase non-negligible deviations from classical predictions, emphasizing the need for accurate quantum treatments in understanding the material's behavior at finite temperatures. At low $T$, the 2D compression modulus of silicene decreases by a 14% due to quantum nuclear motion.