Pressure induced ferroelastic phase transition in LuLiF4 compound
  The behavior of LuLiF4 sheelite (I41/a, Z = 4) under hydrostatic pressure was investigated by means of the first principles calculations. The ferroelastic phase transition from the tetragonal structure of LuLiF4 to fergusonite structure (C12/c1, Z = 4) has been found at 10.5 GPa. It has been determined that this is the second order phase transition. 
Anastasia Petrova, Oleg Nedopekin, Dmitrii Tayurskii, Benoit Minisini
cond-mat.mtrl-sci physics.comp-ph