Electronic structure of two crystallographic forms of BaRuO3

Electronic structure calculations have been performed to explain the differ ence in the electronic properties of two crystallographic forms of BaRuO3. The calculations can explain the qualitatively different resistivities of i soelectronic 4H- and 9R-BaRuO3 below 100 K. The difference in symmetry betw een the hexagonal four-layer BaRuO3 and the rhombohedral nine-layer compoun d allows the formation of a gap for the later. The electronic structure of these hexagonal perovskites is compared with the more familiar cubic perovs kite CaRuO3.