ELECTRONIC-PROPERTIES OF THE ORDERED (ROOT-2X-ROOT-2) SUPERLATTICE PHASES LA2CU0.5LI0.5O4 AND LA2AU0.5LI0.5O4

Linear augmented-plane-wave band-structure results for La2Cu0.5Li0.5O4 , an ordered Cu3+-Li+ superlattice phase that can be formed via Li --> Cu substitution within the CuO2 layers of La2CuO4, predict that this compound is an ordinary band semiconductor with cluster-like features near E(F). The calculated semiconductor gap of similar to 0.7 eV separ ates a narrow (similar to 0.4 eV) filled d(3z2-r2) level from a broade r (similar to 1 eV) unoccupied d(x2-y2) subband. Although a low-lying La 5d band eliminates the corresponding gap in isostructural La2Au0.5L i0.5O4, semiconducting properties would be restored if the recently pr oposed T' structure proves to be correct. Electron or hole doping of t hese cluster-type materials should yield interesting transport propert ies, including possible superconductivity.