An X-ray diffraction study of lithium

An accurate X-ray diffraction investigation has been carried out on two single crystals of lithium. The data from crystal 1 were obtained at temperatures of 248 and 296 K, and those for crystal 2 in the temperature range 293 to 423 K. The measured integrated intensities have been analysed for the presence of anharmonicity in the atomic vibrations by using a temperature factor based on a one-particle potential of the form V(u) = ½ αu² + γu⁴ + δ(u⁴_x + u_y⁴ + u_z⁴ - ⅗u⁴). An average value for the parameter δ of 290 ± 140 eV nm^-4 was found. No significant value of γ was found in the analysis of data from crystal 1, but a value of -360 ± 40 eV nm^-4 was obtained from the higher-temperature data of crystal 2.