Theoretical Study of Electronic Structure and Stability of Mixed AlmBn−mHn2− and CmBn−mHn2−m (n = 6, 10, 12 and m = 1, 2) Clusters

Density functional theory (DFT) method with B3LYP functional and 6-311++G(d,p) basis set has been used to predict the geometries, relative stabilities, electronic structures and bonding analysis of Mixed AlmBn−mHn2− and CmBn−mHn2−m (n = 6, 10, 12 and m = 1, 2) clusters; being compared to the BnHn2− ones. Therefore, the DFT results suggest that the replacing of boron by aluminium or carbon is governed by Natural net charges following Gimar’s and Williams’s rules. The AlmBn−mHn2− structures are relatively distorted compared to those of BnHn2− and CmBn−mHn2−m. In AlmBn−mHn2− structures Al atoms prefer the adjacent sites, however for the C2Bn−2Hn cluster cages, the carbon atoms are positioned at diametrically opposed sites. The large HOMO–LUMO gaps show that the predicted clusters have chemical stabilities, principally, those of AlmBn−mHn2− ones, which are not experimentally isolated. The optimized geometries obtained through boron substitution by Al and C lead to compactness and to contracted structures, respectively, where B–B bonds are the shortest in mono- and di-carbaboranes.