Lattice heat capacity and thermal vibrations in alkali metals

The lattice heat capacity c v ( T ) and mean‐square displacement of the ion, {article}{empty}{document}x² ̄{document} ( T ) in alkali metals are calculated on the basis of the pseudopotential model described earlier. Agreement with experiment is in general quite good for Debye temperatures θ and not bad for the dependences c v ( T ). Some conclusions on the phonon spectrum of Cs are drawn from the data on heat capacity. The pseudopotentials giving a good description of the phonon spectra of Na, K, Rb are proposed. Values of {article}{empty}{document}x² ̄{document} ( T ) are discussed in detail and compared with experiment. The sensitivity of all the results to the approximations for the dielectric function ε( q ) and for the pseudopotential V ( q ) and for the pseudopotential V ( q ) is also discussed.