As discussed in section 2.2, the tetragonal distortion factor, A, represents the tetragonal degree of a crystal. For
example, a cell with A>1 means that this crystal has a tetragonal structure, and cubic structure has a tetragonal
distortion factor A=1. In figure 9, the initial tetragonal distortion factor was about 0.017, or the original structure of
this cell was tetragonal, since no compression was applied. As the pressure increased, the tetragonal distortion (A-1)
decreased from 0.017 at 0 GPa to 0 at about 37 GPa, indicating the tetragonal phase was converting to a cubic
phase, since A was getting closer to 1. After the pressure reached 37 GPa, the tetragonal distortion factor A kept
constant at 1, suggesting that after 37 GPa, the cubic structure became a stable phase