Theory for the first-order vibrational spectra of disordered solids

Expressions are derived in the harmonic approximation which relate the first-order Raman and infrared spectra of a disordered solid to a common set of vibrational densities of states. The calculations assume no periodicity, and using standard approximations lead to expressions involving explicitly defined matrix elements. The results extend those of Shuker and Gammon from Raman to infrared response, and show that the matrix elements involved must be frequency dependent.