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 $\langle h^2\rangle$ and the height-height correlation function $H\left(q\right)$ 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 Gruneisen parameter are estimated to be 25.2 J mol${}^{-1}$ K${}^{-1}$, $7.2\times {10}^{-6}$ K${}^{-1}$, and 0.89, respectively.

• Received 11 June 2012

DOI:https://doi.org/10.1103/PhysRevB.87.184106