Computer modelling of divalent, trivalent and tetravalent ion doping in LiCaAlF6 and LiSrAlF6

This paper describes a computational study of the mixed metal fluorides LiCaAlF6 and LiSrAlF6, doped with divalent (Pb2+, Co2+ and Ni2+), trivalent (Cr3+, Fe3+ and Y3+) and tetravalent (Si4+) ions. For each of the frameworks, all three cation sites were considered, as well as a range of charge compensation mechanisms. For the divalent dopants, substitution at the divalent host site is preferred, whilst for the trivalent dopants, Co3+ and Fe3+ prefer the Al3+ site, and Y3+ shows behaviour similar to the rare earths. Finally, it is found that Al3+ is the preferred site for substitution by Si4+ in both host frameworks