Structural and Electronic Properties of Neutral and Ionic Ga_nO_n Clusters with n = 4—7

Abstract

We report the results of a theoretical study of neutral, anionic, and cationic Ga n O n clusters (n ) 4-7), focusing on their ground-state configurations, stability, and electronic properties. The structural motif of these small gallium oxide clusters appears to be a rhombus or a hexagonal ring with alternate gallium and oxygen atoms. With the increase in the cluster size from Ga 4 O 4 to Ga 7 O 7 , the ground-state configurations show a transition from planar to quasi-planar to three-dimensional structure that maximizes the number of ionic metal-oxygen bonds in the cluster. The ionization-induced distortions in the ground state of the respective neutral clusters are small. However, the nature of the LUMO orbital of the neutral isomers is found to be a key factor in determining the ordering of the low-lying isomers of the corresponding anionic clusters. A sequential addition of a GaO unit to the GaO monomer initially increases the binding energy, though values of the ionization potential and the electron affinity do not show any systematic variation in these clusters.

Theoretical study of small clusters of manganese-doped gallium oxide: Mn(GaO) n and Mn2(GaO) n with n = 1−7

“…Addition of four Ga atoms to MnO 4 forces all the oxygen atoms to be coplanar with the Mn atom. Each Ga atom binds with two oxygen atoms with a large apex angle which tends to facilitate a stronger coupling between Ga s and O p orbitals in the cluster (Deshpande et al 2006) The calculated binding energy 1 of the clusters is given in Table 1. Mn tends to stabilize the host oxide cluster indicating that the addition of a single Mn atom is energetically preferred.…”

“…The equilibrium geometries of the clusters were obtained by quenching a large number of planar and nonplanar configurations of Mn(GaO) n and Mn 2 (GaO) n clusters using the quasi-Newton method (VASP 1999). The choice of some of the initial geometries was partially dependent upon our previous studies of small clusters of gallium oxide (Gowtham et al 2004;Gowtham et al 2005;Deshpande et al 2006). While doping of Mn atom in the pure gallium oxide clusters we have considered all the possible sites for Mn atom in the cluster.…”