Nuclear quadrupole coupling constants in I-III-VI2chalcopyrite semiconductors

The bond-orbital theory of covalent bonding in the ternary chalcopyrite semiconductors has been used to interpret published values for the nuclear quadrupole coupling constants in a number of I-III-${\mathrm{VI}}_2$ materials. Calculations are performed for ${}_{}{}^{63}{}_{}{}^{}\mathrm{Cu}$, ${}_{}{}^{27}{}_{}{}^{}\mathrm{Al}$, and ${}_{}{}^{69}{}_{}{}^{}\mathrm{Ga}$ cations taking account both of lattice and local orbital contributions to electric-field gradients. The theory is shown to be quantitative when applied to those materials for which accurate (single-crystal x-ray) structural details are available. For the others the theory has been used to predict the free intracell chalcopyrite structural parameter for each material and the predictions compared with the less accurately known data from powder x-ray studies. In only one case is any discrepancy apparent.