Electrical, Mechanical and Electromechanical Orders of State Shifts in Nonmagnetic Ferroic Crystals

Abstract

The concepts “ferromagnetic,” “ferroelectric” and “ferroelastic” can be unified and generalized into “ferroic.” In a previous paper it has been found that there are, in all, 773 possible species of ferroic crystals, 212 of which are nonmagnetic. In the present paper, only nonmagnetic ferroic crystals are dealt with. The concepts of electrical, mechanical and electromechanical orders are introduced for state shifts. The ferroelectric (or ferroelastic) state shifts are recognized as electrically (or mechanically) first-order state shifts. Higher-order state shifts are also possible. The three kinds of orders are group-theoretically determined for each state shift in each species. It is seen from this that no species can have more than two unequal electrical orders, more than three unequal mechanical orders or more than two unequal electromechanical orders of state shift. Every species with unequal orders of states shift is “factorized” into species with a single order of state shift.