Structure and stability of the frank-kasper W@Si₁₂, and Ti@Si₁₅ and Ti@Si₁₆ clusters

Ab initio density functional theory plane wave and linear combination of atomic orbitals pseudopotential methods are used to study the stabilities of W@Si₁₂, Ti@Si₁₅ and Ti@Si₁₆ encapsulated clusters. It is shown that three stable W@Si₁₂ isomers and four stable isomers for Ti@Si₁₅ and Ti@Si₁₆ belong to the Frank-Kasper configuration space. Good agreement of the calculated electron affinities with the experimental data provides a clue on the structures of Ti@Si₁₅ which is shown to resemble that for the dimerised Si(001)2 × 1 surface.