Temperature variation of the Debye-Waller factors of Ba⁺⁺ and F^- ions in BaF₂ powder by X-ray diffraction

Abstract

The temperature variation of the Debye-Waller factors of Ba⁺⁺ and F^- ions in BaF₂ powder has been studied using x-ray powder diffraction over the temperature range 77°-298°K. A continuous flow cryostat has been specially fabricated for this purpose for the YPC 50 NM powder diffractometer available in the department. The Debye-Waller factors of Ba⁺⁺ and F^- between room temperature and 879°K have been measured using single crystal neutron diffraction by Cooperet al. Theoretical lattice dynamics shell model calculations using a 7-parameter model in a quasiharmonic approximation have been done over a temperature range 77° to 879°K. The theoretical values have been compared with the present x-ray measurements and the single crystal neutron diffraction values and the results are discussed.