Poisson's ratio for cubic crystals

General expressions for Poisson's ratio are derived for cubic crystals; simplified forms are given for cases involving symmetry directions. Crystals of cubic symmetry include many of the binary semiconductor systems with the piezoelectric zincblende structure, such as GaAs and related alloys. These are extremely important for high technology applications such as cellular radio and microwave collision avoidance radar. All cubic classes have the same elastic matrix scheme, so for our purposes it is not necessary to distinguish between the cubic point groups. The cubic elastic matrix scheme is identical in form to that of isotropic substances; the difference is that for isotropic materials the shear coefficient (s(sub 44) or c(sub 44)) is related to the two other independent coefficients, whereas in cubic crystals it is a third independent quantity.