This work presents for the first time the properties of the liquid phase of silicon carbide using ab initio molecular dynamics simulations based on density-functional theory (DFT). Our DFT scheme employs a plane-wave basis to expand the atomic orbitals, pseudopotentials built with the projector augmented wave method, and the local-density approximation to describe the exchange–correlation interactions. With this approach we we determine a melting temperature of the zinc-blend phase of 2678.54 ( ± 41.67) K with a pressure of 0.25 (± 0.40) GPa and a density of 3.06 g/cm3 in good agreement with the experimental normal melting point of 2818.00 (± 40.00) K. At these conditions, the diffusion coefficient of the melt is 6.86 x 10−3 nm2/ps which compares well with the estimated value of 2.46 x 10−3 nm2/ps in the experiments done at atmospheric pressure. Finally, our model shows that silicon carbide has a negative melting curve that qualitatively agrees with experiments, with a slope of -36.93 K/GPa with pressures between 2.56 and 6.48 GPa, which compares well with the -44 K/GPa reported from the laboratory carried out with pressures of up to 7.7 GPa. This work provides a straightforward methodology based on the popular ’Z-method’ to produce liquid systems of silicon carbide, from which amorphous systems can easily be then produced by quenching.
Saiz, F. (2020). An ab initio study on liquid silicon carbide. Journal of Physics and Chemistry of Solids, 137. https://doi.org/10.1016/j.jpcs.2019.109204