Phenomenological theory of high-pressure induced phase transitions in Ga-, In-, and Al-mononitrides

Discovery of a new phase transition in gallium nitride at 22 GPa

“…The phenomenological the ory of phase transitions under pressure with a change in symmetry is very different from the theory of phase tran sitions upon a change in temperature [11][12][13].…”

“…Con sidering the changes in symmetry in the models of [11][12][13] allowed us to better match the numerical val ues of the second order modulus of elasticity to the data from acoustic measurements. Technically, how ever, it could be seen as a result of introducing an addi tional phenomenological parameter into the theory.…”