The bonding in hexagonal Ba2/3Pt3B2 and CeCo3B2 type ternary metal borides

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摘要：

Tight-binding calculations with an extended Hückel Hamiltonian were performed on Ba 2/3 Pt 3 B 2 and LuOs 3 B 2 . Hypothetical linear metal boride chains present in these materials are analyzed with a three-dimensional model that contains a trigonal bipyramidal T 3 B 2 (T=transition metal) building unit for the compounds. The geometrical structure for the T 3 B 2 trigonal bipyramids depends on the number of electrons. For systems that have greater than 36 electrons in its trigonal bipyramidal building unit, a structural distortion is expected. Electron back donation from the electron-rich M 3 fragment to the empty e′ set on B 2 creates boron–boron interaction along the z -axis. Boron–boron pairing then participates as an electron sink and causes a trigonal distortion of the platinum Kagome net. On the other hand, a system with <35 electrons should have an undistorted, CeCo 3 B 2 type structure. The electronic factors that create the breathing motion are discussed and analyzed with the aid of molecular and solid-state models. The metal–metal bonding associated with the structural properties also has been examined.

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关键词：

Tight-binding calculations Transition metal borides Band structure calculations Kagome net

DOI：

10.1007/s00214-012-1091-4

年份：

2012