Can a linear anisotropic elastic material have a uniform contraction undera uniform pressure?

When a linear isotropic elastic material is under a uniform pressure, it pr oduces a uniform contraction. If the material is anisotropic, it in general does not produce a uniform contraction except for a cubic material. We wil l show that there are special linear anisotropic elastic materials other th an cubic materials for which a uniform contraction is possible under a unif orm pressure. The material can be any one of the eight crystal groups. It m eans that the material can be monoclinic, orthotropic, trigonal, tetragonal , transversely isotropic, and, of course, cubic or isotropic. It can also b e triclinic; that is, the material need not possess a plane of symmetry.