Theoretical study of the structures, stabilities, and electronic properties of neutral and anionic Ca2Si n λ (n = 1–8, λ = 0, +1) clusters

Abstract

The structures, stabilities and electronic properties of neutral and cationic, calcium-doped, small silicon clusters Ca2Si (n = 1–8, λ = 0, +1) have been systematically investigated by using the density functional theory method at the B3LYP/6-311G (d) level. The results show that the ground state optimal structures of the cationic and neutral clusters favour the three-dimensional structures for n = 3−8 respectively, and that the cationic Ca2Si + clusters have the lowest-energy structures similar to those of neutral Ca2Si n clusters with the exception of Ca2Si 6 + . The main configurations of the Ca2Si n isomers are not affected by removal of an electron, but the order of their stability is reversed. Based on the optimised geometries, the averaged binding energy (E b ), fragmentation energy (E f ), second-order energy difference (Δ 2 E), HOMO-LUMO energy gap (E gap ), adiabatic ionisation potential (AIP) and vertical ionisation potential (VIP) are analysed for the most stable structures. We found that Ca2Si5, Ca2Si7 and Ca2Si 7 + clusters have the strongest relative stability, and that the positive charged clusters are more stable than the corresponding neutral ones.