Coexistence of Local and Band Characters in the Absorption Spectra of Solids. II. Calculations for the Simple Cubic Lattice

Line shapes of the fundamental absorption and the impurity-induced infrared absorption of lattice vibrations are calculated in order to clarify the complementary interplay of the local and band characters. The shift-broadening matrix method is applied to a monatomic simple cubic lattice with nearest neighbor interaction. As one varies the short range electron-hole attractive potential in the electronic case or the mass and the force constant of the impurity in the vibrational case, Van Hove singularities undergo a metamorphism. A variety of shapes appear in the spectra as the result of the interplay of the both characters. A few remarks are made concerning the available experimental data.