Open Access. Powered by Scholars. Published by Universities.®
Articles 1 - 1 of 1
Full-Text Articles in Physics
Theoretical Study Of The Structural Phase Transition In Rbcaf3, L. L. Boyer, John R. Hardy
Theoretical Study Of The Structural Phase Transition In Rbcaf3, L. L. Boyer, John R. Hardy
John R. Hardy Papers
We have made a first-principles study of the structural phase transition at Tc = 193 K in RbCaF3, using interionic potentials derived by the Gordon-Kim approach, and a new extension of the quasiharmonic approximation for the free energy. The transition is caused by instability of a triply degenerate R-point vibration which leads to a coordinated rotation of the CaF6 octahedra. We find that, as the lattice contracts, the quasiharmonic frequency of the R-point vibrations becomes imaginary at approximately 1280 K: Below this temperature the static lattice energy, as a function of CaF6 rotation, has a …