SOME FACTORS INFLUENCING METAL-INSULATOR TRANSITIONS

Three problems are studied. (i) The optimal shape of the electronic de nsities of states of metal and gapped insulator related by a geometric al distortion, for a temperature induced transition between them. (ii) The dependence of valence band width on cation identity and the tempe rature of the metal-Mott-Hubbard insulator transition in the series RE NiO(3) (RE = Rare Earth). (iii) Electronic insights into the loss of a Jahn-Teller distortion at Mn during the insulator-metal transition in La1-xSrxMnO3 as x increases but not at Cu for La2-xSrxCuO4.