Quantum effects in two-dimensional silicon carbide

Two-dimensional (2D) silicon carbide is an emergent direct band-gap\nsemiconductor, recently synthesized, with potential applications in electronic\ndevices and optoelectronics. Here, we study nuclear quantum effects in this 2D\nmaterial by means of path-integral molecular dynamics (PIMD) simulations in the\ntemperature range from 25 to 1500~K. Interatomic interactions are modeled by a\ntight-binding Hamiltonian fitted to density-functional calculations. Quantum\natomic delocalization combined with anharmonicity of the vibrational modes\ncause changes in structural and thermal properties of 2D SiC, which we quantify\nby comparison of PIMD results with those derived from classical molecular\ndynamics simulations, as well as with those given by a quantum harmonic\napproximation. Nuclear quantum effects are found to be appreciable in\nstructural properties such as the layer area and interatomic distances.\nMoreover, we consider a {\\em real} area for the SiC sheet, which takes into\naccount bending and rippling at finite temperatures. Differences between this\narea and the in-plane area are discussed in the context of quantum atomic\ndynamics. The bending constant ($\\kappa = 1.0$ eV) and the 2D modulus of\nhydrostatic compression ($B_{xy}$ = 5.5 eV/\\AA$^2$) are clearly lower than the\ncorresponding values for graphene. This study paves the way for a deeper\nunderstanding of the elastic and mechanical properties of 2D SiC.\n