First-principles study of Ga7As7 ionic cluster and influence of multi-charge on its structure

This paper investigates the structures and stabilities of neutral Ga₇As₇ cluster and its ions in detail by using first-principles density functional theory. Many low energy structures of Ga₇As₇ cluster are found. It confirms that the ground state structure of neutral Ga₇As₇ cluster is a pentagonal prism with four face atoms like a basket structure, as reported by previous works. The ground state structures of positive Ga₇As₇ cluster ions are different from that of the neutral cluster. These investigations suggest that Ga atoms occupy the capping positions more easily than As atoms. Mulliken population analyses also show that Ga atoms can lose or obtain charge more easily than As atoms. It finds that the neutral Ga₇As₇ cluster can become more stable by gaining one or two additional electrons but further more electrons would cause the decrease of binding energy. The ionisation energy increases with the increase of the number of the removed electrons. These calculated results indicate that the net magnetic moment of the neutral Ga₇As₇ cluster is zero because all electrons are paired together in their respective molecular orbits. But for the ionic Ga₇As₇ cluster with odd number of electrons, the net magnetic moment is 1.0 μ_B due to an unpaired electron.