Ab-initio investigations of icosahedral boron compounds with Al, Mg, C, O, Si atoms

The geometry and cohesive energy of isolated clusters — fragments of icosahedral boron compounds — with Al, Mg, C, O, Si substitution atoms have been calculated within the framework of DFT electron density theory using the Gamess software package. Electron density distribution between atoms has been investigated. The bulk modulus of the B12 cluster has been calculated on the basis of quantum chemical calculations and a thermodynamic series of cluster hardness has been constructed: HB22O2 > HB22C2 > HB24 > HB22Si2 > HB22Al2 > HB22Mg2. The calculated bulk modulus and hardness values based on the results of the first-principles study of the clusters are in good agreement with the experimental data for compounds with similar chemical compositions. The technique is applicable to the prediction of the choice of substitutional atoms in icosahedral boron groupings. Keywords: boron, boride, isolated cluster model, bulk modulus, hardness.