Pressure Induced Structural Changes in Cesium Fluoride: Theory and Experiment

We have investigated pressure induced structural changes in cesium fluoride using density functional theory and synchrotron X-ray diffraction (XRD) measurements. The calculated total energy and enthalpy clearly indicate that the B1 → B2 transition occurs near 5 GPa, which is confirmed by our high pressure synchrotron XRD study of cesium fluoride (CsF), up to 120 GPa. It is found that no phase transitions were observed between 5 -120 GPa experimentally in this study. Unit cell data were determined from the known B2 (CsCl) structure for all of the pressures studied above 5 GPa, and an equation of state (EOS) was fit to the data using a 3rd order Birch–Murnaghan equation in this phase. The Density Functional Theory (DFT) calculations were also carried out to compute an EOS and bulk modulus. Our experimental results agreed very well with the predicted bulk modulus and EOS data from DFT.