Raman and photoelastic constants and impurity absorption in valency crystals

Abstract

The vibrational absorption of a charged impurity in valency crystals has recently been discussed by the authors. It was concluded that the absorption by the impurity is determined mainly by non- electrostatic short-range effects, while the actual charge on the impurity is only of secondary importance. A part of this argument was based on a relation which contained the photoelastic constants of the pure valency crystals; in that relation the fact was neglected that in a diamond lattice an xy shear induces an 'optical' displacement in the z direction and that the measured photoelastic constant p₄₄ includes the effect of this optical displacement. In the present paper the effect of the optical displacement is investigated and it is shown that it does not affect the previous conclusions.