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Abstract: The electronic structures of the metal-rich phosphides LiCo6P4 and Li2Co12P7 were studied by DFT calculations. Both phosphides consist of three-dimensional [Co6P4] and [Co12P7] polyanionic networks which leave hexagonal channels for the lithium atoms. COOP data show strong Co–P and Co–Co bonding within the polyanions. The lithium atoms have trigonal prismatic phosphorus coordination. Total energy calculations indicate stability upon de-lithiation towards the Co6P4 and Co12P7 substructures [Copyright &y& Elsevier]

Abstract: Despite similarities in formulae and local structures of Zr2CoH5 and Mg2CoH5, they are shown from ab initio calculations to present contrasted electronic, magnetic, mechanical and bonding properties due to the environment of cobalt with hydrogen characterized by negatively charged CoH x entities (x=4, 5 resp.) and to the chemical nature of Zr versus Mg. Zr2CoH5 is found more cohesive, harder and less ductile than Mg2CoH5. High density of states at the Fermi level arises from out-of-plane non-bonding Co-d z 2 in Zr2CoH5 which is found as metallic ferromagnet in the ground state, in contrast with non-magnetic and insulating Mg2CoH5. [Copyright &y& Elsevier]

Abstract: The dimorphism of the intermediate valence ternary cerium silicide CeIr2Si2 in the ThCr2Si2 (α) and CaBe2Ge2 (β) modifications is addressed in the framework of the density functional theory. The geometry optimization is in good agreement with the experiment and the subsequent establishment of the energy–volume equation of state (EOS) indicates a stabilization of the β-type relative to the α-type concomitant with the trend of the cerium valence, changing to tetravalent in β-CeIr2Si2. This is equally shown from the site projected DOS and from the large increase of the electronic contribution to the specific heat. The chemical bonding indicates the strongest bonding interactions within the Ir–Si substructure in both varieties. Stabilization of β-CeIr2Si2 with almost tetravalent cerium is in good agreement with ThIVIr2Si2 which exclusively crystallizes in the CaBe2Ge2 type. The EOS behavior of different RIr2Si2 (R=Th, Ce, La) is comparatively discussed. [Copyright &y& Elsevier]