Electronic structure and interatomic bonding in Al10V

On the basis of ab initio calculations we analysed the electron density distribution in the elementary cell of the compound Al10V. We found covalent bonding between certain atoms. The Al–V bonds of enhanced covalency are linked into –Al–V–Al–V– chains that extend over the whole crystal. The chains intersect at each V site and together form a Kagome network of corner-sharing tetrahedra. The large voids of this network are filled by Z16 Friauf polyhedra consisting of Al atoms only. The skeleton of the Friauf polyhedron has the form of a truncated tetrahedron and consists of 12 strongly bonded Al atoms. These Al–Al bonds also have covalent character. The bonding is dominated by sp2 hybridization. The centre of the Friauf polyhedron may be empty or occupied by an Al atom. The thermodynamic stability of the phase is investigated. The Al21V2 phase with occupied voids is at low temperatures less stable than Al10V. The Al10V structure can be considered as a special case of the Al18Cr2Mg3 structural class. We have found the same picture of bonding as we report here for Al10V for several other aluminium-rich alloys belonging to the Al18Cr2Mg3 structural class also.