Orthorhombic intermediate state in the zinc blende to rocksalt transformation path of SiC at high pressure.
The mechanism of the B3/B1 phase transition of SiC has been investigated by periodic LCAO-DFT least-enthalpy calculations. A new transformation pathway, based on a Pmm2 orthorhombic intermediate state with two SiC units per cell, is found to be energetically favored over the traditional R3m mechanism. The computed activation enthalpy is 0.75 eV/SiC unit at the predicted transition pressure of 92 GPa (B3LYP functional). Activation enthalpy and activation volume vs pressure are analyzed to characterize the kinetic aspects of the transformation.
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Dipartimento di Scienza dei Materiali, Università di Milano Bicocca, 20125, Milano, Italy.