S. Fabris et al., Free energy and molecular dynamics calculations for the cubic-tetragonal phase transition in zirconia - art. no. 094101, PHYS REV B, 6309(9), 2001, pp. 4101
The high-temperature cubic-tetragonal phase transition of pure stoichiometr
ic zirconia is studied by molecular dynamics (MD) simulations and within th
e framework of the Landau theory of phase transformations. The interatomic
forces are calculated using an empirical, self-consistent, orthogonal tight
-binding model, which includes atomic polarizabilities up to the quadrupola
r level. A first set of standard MD calculations shows that, on increasing
temperature, one particular vibrational frequency softens. The temperature
evolution of the free-energy surfaces around the phase transition is then s
tudied with a second set of calculations. These combine the thermodynamic i
ntegration technique with constrained MD simulations. The results seem to s
upport the thesis of a second-order phase transition but with unusual, very
anharmonic behavior above the transition temperature.