The Equivalents of Unique Ferroelectric Direction in the Paraelectric Crystal Having a Ferroelectric Phase Transition and the Possible Kinds of the Corresponding Ferroelectric Phase

It was found by previous studies that the ferroelectrics are divisible into 25 kinds in accordance with their point groups, space lattices, and types of state transition. With the aid of this result, the ferroelectric phase transition of the paraelectric crystal is investigated in a systematic way. When the point group, and only that, of the paraelectric crystal is specified, a determination is made of the total number of equivalent unique ferroelectric directions, the orientation of one of the equivalent unique ferroelectric directions, the angle between the equivalent unique ferroelectric directions, and the possible kinds of the ferroelectric phase. All of the 32 point groups are taken into consideration as the above point group of the paraelectric crystal. The results are tabulated