Browsing by Author "Leoni, Stefano"

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    All-t2g electronic orbital reconstruction of monoclinic MoO2 battery material
    (Basel : MDPI, 2020) Craco, Luis; Leoni, Stefano
    Motivated by experiments, we undertake an investigation of electronic structure reconstruction and its link to electrodynamic responses of monoclinic MoO2. Using a combination of LDA band structure with DMFT for the subspace defined by the physically most relevant Mo 4d-bands, we unearth the importance of multi-orbital electron interactions to MoO2 parent compound. Supported by a microscopic description of quantum capacity we identify the implications of many-particle orbital reconstruction to understanding and evaluating voltage-capacity profiles intrinsic to MoO2 battery material. Therein, we underline the importance of the dielectric function and optical conductivity in the characterisation of existing and candidate battery materials.
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    Novel metastable metallic and semiconducting germaniums
    ([London] : Springer Nature, 2013) Selli, Daniele; Baburin, Igor A.; Martoňák, Roman; Leoni, Stefano
    Group-IVa elements silicon and germanium are known for their semiconducting properties at room temperature, which are technologically critical. Metallicity and superconductivity are found at higher pressures only, Ge β-tin (tI4) being the first high-pressure metallic phase in the phase diagram. However, recent experiments suggest that metallicity in germanium is compatible with room conditions, calling for a rethinking of our understanding of its phase diagram. Missing structures can efficiently be identified based on structure prediction methods. By means of ab initio metadynamics runs we explored the lower-pressure region of the phase diagram of germanium. A monoclinic germanium phase (mC16) with four-membered rings, less dense than diamond and compressible into β-tin phase (tI4) was found. Tetragonal bct-5 appeared between diamond and tI4. mC16 is a narrow-gap semiconductor, while bct-5 is metallic and potentially still superconducting in the very low pressure range. This finding may help resolving outstanding experimental issues.