Polytypic transformations in SiC: An ab initio study

Solid-solid phase transitions in SIC between two polytypes are investigated within an nb initio density-functional scheme, starting from a model based upon dislocations. As an example, the transformation from 6H SiC into the 3C polytype is studied in detail. The energy barrier for twinning a tetrahe dron is calculated to be about 0.77 eV per bond. It indicates that the disl ocation mechanism may be responsible for the temperature- and deformation-i nduced transitions observed experimentally. [S0163-1829(99)14139-0].