Anharmonicity and the low-temperature phase in lithium metal

Neutron diffraction experiments have been carried out on high-purity ⁷Li at various temperatures between 4.2 and 300 K. Certain features of the diffraction data indicate that the low-temperature structure is more complicated than simple hcp. The Debye-Waller factor has also been measured using the incoherent elastic scattering by ⁷Li and large anharmonic contributions at all temperatures have been found.