Structural evolution of inorganic Si Pd2 (n = 1–17) clusters

The structures of silicon clusters doped with two palladium atoms have been explored using an unbiased global optimization technique, and the candidate structures further analyzed using density functional theory. The optimized geometries, stabilities, and electronic structures of Si 1 Pd 2 – Si 17 Pd 2 are reported, and several new lowest energy isomers are located for the first time impacting the relative cluster stabilities. Based on the relative energies, Si 5 Pd 2 , Si 10 Pd 2 , and Si 16 Pd 2 are predicted to be the most stable clusters for the sizes considered here. A growth pattern in this size range is noted that primarily consists of trigonal and pentagonal structural motifs, the latter dominating for larger clusters once Pd atoms become encompassed in the silicon cluster framework. Palladium atoms bind exohedrally to the base cluster for smaller sized clusters, but begin to bind endohedrally once the cluster size reaches Si 11 Pd 2 (for the first Pd atom) and Si 16 Pd 2 (for the second Pd atom). Detailed analysis of the cluster’s electronic structure indicate that palladium atoms have only a small partial charge, and that the frontier molecular orbitals consist primarily of palladium d and silicon p atomic orbitals. Total electron density plot and structure of the Si 16 Pd 2 cluster. • Si n Pd 2 ( n = 1-17) clusters are studied using hybrid density functional theoretical techniques • Unbiased global optimization method is used for the first time to determine new global minima Si n Pd 2 structures • Si 5 Pd 2 , Si 10 Pd 2 , and Si 16 Pd 2 are determined to be the most stable clusters in this size range • Ground state structures tend to possess trigonal and pentagonal structural motifs • Pd atoms begin to bind endohedrally for Si 11 Pd 2 (first Pd) and Si 16 Pd 2 (second Pd) • Frontier molecular orbitals are composed primarily of palladium d and silicon p atomic orbitals in each cluster