CRYSTAL BINDING AND ELASTIC CONSTANTS — Charles Kittel
Physics — Solid State · elastic-waves-cubic-crystals
Problem
Determinantal approach. It is known that an R-dimensional square matrix with all elements equal to some constant c has eigenvalues Rc (once) and 0 (R−1 times). Using this result, write down at once the dispersion relation for elastic waves in the [111] direction of a cubic crystal.