Molecular-Dynamics Simulation of the Structural Phase Transition in Rb\u3csub\u3e2\u3c/sub\u3eCaCl\u3csub\u3e4\u3c/sub\u3e

We have simulated the structural phase transition of one member of A2BX4 layered perovskite-like compounds, Rb2CaC14. This family of compounds may be thought of as being constructed from normal perovskite unit cells but with a different stacking arrangement. In recent months, this structural family has become extremely important since it is the parent structure from which the new class of high-temperature superconductors comes from. The simulation was done using ab initio potentials with no adjustable parameters. Our calculations show a specific-heat anomaly at 400 K which corresponds to an observed pseudorotation of the CaCl6 octahedral group. This rotation is similar to the structural phase transitions observed in the perovskite-structure family. We also postulate a dynamically disordered high-temperature structure for this compound