Anharmonicity of lattice vibrations in white tin by X-ray measurement of almost-forbidden reflections

The intensities of the almost-forbidden reflections 822, 10 4 2, and 12 2 2 in a single crystal of white tin have been measured at 300 K using Mo Kα radiation. Careful checks for the absence of multiple Bragg reflections were made. The data are interpreted in terms of anharmonic atomic vibrations by applying the effective one-particle potential formalism. The cubic anharmonic force constant α32+ is estimated from the experimental data to be (0.63 ±0.05) × 10−12erg A−3. A considerable discrepancy with another recent study is discussed.