Electron energy bands and cohesive properties of CsCl, CsBr, and CsI

Results of self-consistent first-principles calculations of the electronic band structures of the three cesium halides within the local-density functional formalism are presented. The calculations were done with the linear muffin-tin orbital (LMTO) method and relativistic effects were taken into account. The general features of the electron bands in the three compounds are very similar. In all cases the isotropic Γ₆⁺ state forms the conduction-band bottom as has been speculated earlier. Effective-mass parameters for the valence and conduction bands are obtained by fitting our bands with the results of k{·}p perturbation theory. The nature of cohesion in the three compounds is discussed within the LMTO framework. The calculated total energy fits very well with the total energy as given by the Born-Mayer model for ionic compounds over a large range of crystal volume.