Molecular approach to the modeling of elasticity and piezoelectricity of SiC polytypes

We present the results of a lattice-dynamical treatment of the 3C, 2H, 4H, and 6H structures of SiC, performed within the framework of an unified approach. This includes (i) a simple valence force field, whose parameters were in part derived from the quantum-mechanical calculations of the appropriate molecule, in part from a fitting procedure, and (ii) a charge distribution model regarding the electron transfer between bonded atoms as a response to the change of interatomic separation. A conflict exists in the literature about the elastic properties of 3C-SiC, and our opinion on the most reliable data is given. Complete sets of elastic and piezoelectric tensor elements derived from the model calculations are presented for all materials under consideration. The chemical regularity in the variation of sign of the e₁₄ piezoelectric constants from the I-VII to IV-IV members of the sphalerite family is discussed in light of the present model.