Abstract
We apply a constant-pressure ab initio technique to investigate the high-pressure phase transformation of 6H-SiC and show that it transforms into a rocksalt structure. This phase change proceeds in two stages: 6H-SiC is first compressed along the c-direction and then it undergoes a shear deformation on the a-b planes. This transformation mechanism is quite similar to that of the wurtzite-to-rocksalt observed in 2H-SiC but there is no metastable phase identified along this path. The 6H-to-RS phase transition is also analyzed from the energy volume calculations. The computed transition parameters agree well with the experimental data.