Suchergebnisse

57th European High Pressure Research Group Meeting on High Pressure Science and Technology (EHPRG2019) in Prague, 1-6 september 2019 ; Metavalent or resonant bonding is a recently proposed new class of bonding that is intermediate between p-type covalent bonding and metallic bonding. It characterizes a new family of materials known as "incipient metals" [1]. Metavalent bonding occurs in materials where there is a deficiency of valence electrons in the unit cell to form a large number of bonds, such as in octahedrally-coordinated rocksalt-related structures occurring in GeTe, SnTe, PbSe, PbTe, Sb2Te3, Bi2Te3, Bi2Se3, Sb, Bi and AgSb2Te4. The main characteristics of metavalent bonding are: i) a much higher cation coordination than that assumed with the 8-N rule; ii) very high Born effective charge and optical dielectric constant as compared to typical covalent materials; iii) high mode Grüneisen parameters of phonons and low wavenumbers of optical phonons as compared to typical covalent materials; and iv) a moderately high electrical conductivity caused by thesmall bandgap which stems from the partial delocalization of electrons between several bonds ; This work has been financially supported by Spanish MINECO under projects FIS2017-83295-P and MAT2016-75586-C4-1/2/3-P and by Generalitat Valenciana under project PROMETEO/2018/123-EFIMAT. Supercomputer time has been provided by the Red Española de Supercomputación (RES) and the MALTA cluster. JAS acknowledges "Ramón y Cajal" fellowship (RYC-2015-17482) and E.L.d.S acknowledges Marie Sklodowska-Curie grant No. 785789-COMEX from European Union's Horizon 2020 research and innovation programme. We also thank ALBA synchrotron for funded experiments.