Path-integral Monte Carlo simulations on the thermodynamic properties of single-layer hexagonal boron nitride
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2022
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We investigate the quantum effects and anharmonicity on the thermodynamical properties of single-layer hexagonal boron nitride (SL-hBN) using quantum path-integral Monte Carlo (PIMC) and classical Monte Carlo (CMC) simulations in the isothermal–isobaric ensemble at zero pressure. The quantum effects are extracted from the differences between the results obtained from the PIMC and CMC calculations. Our numerical simulations show that the out-of-plane motion of the atoms plays a decisive role in the negative thermal expansion of the SL-hBN crystal and the quantum zero-point vibrational energy greatly enhances the negative thermal expansion coefficients. We demonstrate for the first time the anisotropic thermal expansions in SL-hBN crystal manifested in the different linear thermal expansion coefficients in the zig-zag and armchair directions. Such an anisotropic effect can be significant at high temperatures. From an analysis of the atomic kinetic and potential energy contributions in the thermal vibration energy of the crystal lattice, we find that the anharmonicity of the SL-hBN crystal lies on the ground of the asymmetric thermal vibrations of the boron and nitrogen atoms and their coupling in the same unit cell of the hexagonal lattice.
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Single-layer hexagonal boron nitride, Path integral Monte Carlo, Thermodynamic properties
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BRITO, B. G. A. et al. Path-integral Monte Carlo simulations on the thermodynamic properties of single-layer hexagonal boron nitride. Computational Condensed Matter, Amesterdam, v. 31, e00660, 2022. DOI: 10.1016/j.cocom.2022.e00660. Disponível em: https://www.sciencedirect.com/science/article/pii/S235221432200020X. Acesso em: 19 jan. 2024.