OPTICAL-PROPERTIES OF THE GROUP-IVB REFRACTORY-METAL COMPOUNDS

We have calculated ab initio the direct interband electric dipole tran sitions of the carbides, nitrides, and oxides of Ti, Zr, and Hf in the rocksalt structure using the full-potential linear muffin-tin orbital method. The dipole matrix elements are calculated explicitly. Our res ults are in extraordinarily good agreement with experiment. The optica l spectra are analyzed and we explain the origin of the different stru ctures in the spectra in terms of the calculated electronic structure. We also discuss the trends in the optical properties as the metal and nonmetal atom types are changed and how these trends relate to genera l concepts such as band filling, nuclear charge, and bandwidth.