Thermomechanical properties of a single hexagonal boron nitride sheet

TL;DR

This study uses atomistic simulations to analyze the thermomechanical properties of single-layer hexagonal boron nitride, comparing its behavior to graphene up to 1000 K, revealing differences in stiffness, buckling, and thermal responses.

Contribution

The paper provides the first detailed comparison of thermomechanical properties of h-BN and graphene, highlighting the temperature-dependent stiffness and buckling behavior of h-BN.

Findings

h-BN is less stiff than graphene at room temperature

Buckling transition in h-BN depends on compression direction

Thermal properties like heat capacity and expansion coefficient are quantified

Abstract

Using atomistic simulations we investigate the thermodynamical properties of a single atomic layer of hexagonal boron nitride (h-BN). The thermal induced ripples, heat capacity, and thermal lattice expansion of large scale h-BN sheets are determined and compared to those found for graphene (GE) for temperatures up to 1000 K. By analyzing the mean square height fluctuations $< h^2>$ and the height-height correlation function $H(q)$ we found that the h-BN sheet is a less stiff material as compared to graphene. The bending rigidity of h-BN: i) is about 16% smaller than the one of GE at room temperature (300 K), and ii) increases with temperature as in GE. The difference in stiffness between h-BN and GE results in unequal responses to external uniaxial and shear stress and different buckling transitions. In contrast to a GE sheet, the buckling transition of a h-BN sheet depends strongly on the direction of the applied compression. The molar heat capacity, thermal expansion coefficient and the Gruneisen parameter are estimated to be 25.2 J\,mol$^{-1}$\,K$^{-1}$, 7.2$\times10^{-6}$K$^{-1}$ and 0.89, respectively.