Phonon dispersion and defect energies for rubidium chloride, bromide, iodide, and sulphide

New crystal potentials have been developed for rubidium chloride, bromide,i odide, and sulphide, and also strontium chloride, by first calculating the pair-interactions in the electron-gas approximation and then refitting the potential parameters to available crystal properties. These potentials were then further tested by calculating the phonon dispersion in these material s along principal symmetry directions, with generally good agreement with e xperiment (except for rubidium sulphide for which no experimental neutron s cattering data are available). The potentials were then used in the HADES c omputer code to calculate the energies of formation and migration of point defects in these materials. Our calculations indicate that several transpor t mechanisms may be important in the Rb halides and this has been verified in the case of RbCl by a recent very detailed analysis of the ionic conduct ivity of pure and doped RbCl.