Abstract

The Debye-Waller factors of KBr have been determined both by X-ray and by neutron diffraction methods. Previous experiments have been carried out at or above room temperature. No such measurements have been reported at 4.2 K. Neutron diffraction experiments on a KBr powder at 295 and 4.2 K are reported here. The experimental results obtained were BK = 2.55 plus or minus 0.07, BBr = 2.20 plus or minus 0.04 A2 at T = 295 K, and BK = 0.43 plus or minus 0.05, BBr = 0.35 plus or minus 0.02 A2 at 4.2 K. These values differ from the theoretical estimates of Reid & Smith J. Phys. Chem. Solids (1970), 31, 2689-2697, based on a quasiharmonic approximation using the shell model. The discrepancy may be attributed to the partial neglect of anharmonicity in the theoretical estimates.