Planar vs. three-dimensional X-6(2-), X2Y42-, and X3Y32- (X, Y = B, Al, Ga) metal clusters: an analysis of their relative energies through the turn-upside-down approach

Despite the fact that B and Al belong to the same group 13 elements, the B-6(2-) cluster prefers the planar D-2h geometry, whereas Al-6(2-) favours the Oh structure. In this work, we analyse the origin of the relative stability of D2h and Oh forms in these clusters by means of energy decomposition analysis based on the turn-upside-down approach. Our results show that what causes the different trends observed is the orbital interaction term, which combined with the electrostatic component do (Al-6(2-) and Ga-6(2-)) or do not (B-6(2-)) compensate the higher Pauli repulsion of the Oh form. Analysing the orbital interaction term in more detail, we find that the preference of B-6(2-) for the planar D-2h form has to be attributed to two particular molecular orbital interactions. Our results are in line with a dominant delocalisation force in Al clusters and the preference for more localised bonding in B metal clusters. For mixed clusters, we have found that those with more than two B atoms prefer the planar structure for the same reasons as for B-6(2-)

Structure, reactivity and electronic properties of V-doped Co clusters

Structures, physical and chemical properties of V doped Co$_{13}$ clusters have been studied in detail using density functional theory based first-principles method. We have found anomalous variation in stability of the doped clusters with increasing V concentration, which has been nicely demonstrated in terms of energetics and electronic properties of the clusters. Our study explains the nonmonotonic variation in reactivity of Co$_{13-m}$V$_m$ clusters towards H$_2$ molecules as reported experimentally [J. Phys. Chem. {\bf 94}, 2744 (1990)]. Moreover, it provides useful insight into the cluster geometry and chemically active sites on the cluster surface, which can help to design better catalytic processes.Comment: 10 pages, 9 figures, 4 table

Theoretical Studies of the Structure and Stability of Metal Chalcogenide CrnTem (1≤n≤6, 1≤m≤8) clusters

In the presented work, first principle studies on electronic structure, stability, and magnetic properties of metal chalcogenide, CrnTem clusters have been carried out within a density functional framework using generalized gradient functions to incorporate the exchange and correlation effects. The energetic and electronic stability was investigated, and it was found that they are not always correlated as seen in the cluster Cr6Te8 which has smaller gap between its HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) and a high electron affinity of 3.39 eV indicating lower electronic stability whereas higher fragmentation energy indicating energetic stability. The high electron affinity shows that the stability of Cr6Te8 cluster can be enhanced by adding charge donating ligands including PEt3 to form stable Cr6Te8(PEt3)6 clusters as seen in experiments. The other cluster of interest was Cr4Te6 in which energetic stability was accompanied with electronic inertness marked by its large HOMO-LUMO gap, non-magnetic ground state and high fragmentation energy