Debye Characteristic Temperatures of Certain Noncubic Crystals

The Debye characteristic temperatures of noncubic crystals with a principal axis of symmetry are evaluated by an expansion of the integrand involved in terms of harmonic polynomials having the same symmetry as the corresponding Christoffel equations of elasticity theory. We have applied our method to representative hexagonal, tetragonal, and trigonal crystals and examined the question of its convergence. The absolute values of the characteristic temperatures obtained here are unreliable because of a lack of 0^∘{}K elastic constants for the crystals concerned.