Lei Xue-Ling

Theoretical study of small Mo clusters and molecular nitrogen adsorption on Mo clusters

This paper studies the small molybdenum clusters of Mon (n = 2–8) and their adsorption of N2 molecule by using the density functional theory (DFT) with the generalized gradient approximation. The optimized structures of Mon clusters show the onset of a structural transition from a close-packed structure towards a body-centred cubic structure occurred at n = 7. An analysis of adsorption energies suggests that the Mo2 is of high inertness and Mo6 cluster is of high activity against the adsorption of N2. Calculated results indicate that the N2 molecule prefers end-on mode by forming a linear or quasi-linear structure Mo—N—N, and the adsorption of nitrogen on molybdenum clusters is molecular adsorption with slightly elongated N-N bond. The electron density of highest occupied molecular orbital and lowest unoccupied molecular orbital, and the partial density of states of representative cluster are also used to characterize the adsorption properties of N2 on the sized Mon clusters.

Equilibrium geometries and electronic properties of BenLi (n = 2–15) clusters from first principles

This paper studies the equilibrium geometries and electronic properties of Ben and BenLi clusters, up to n = 15, by using density-functional theory(DFT) at B3LYP/6–31G(d) level. The lowest-energy structures of Ben and Ben Li clusters were determined. The results indicate that a single lithium impurity enhances the stability and chemical reactivity of the beryllium clusters. It finds that the geometries of the host clusters change significantly after the addition of the lithium atom for n ≥8. The lithium impurity prefers to be on the periphery of beryllium clusters, and occupies vertex sites. Both Be4 Li, Be9Li, and Be13 Li were found to be particularly stable with higher average binding energy, local peaks of second-order energy difference and fragmentation energies. For all the Ben Li clusters studied, we found charge transfers from the Li to Be site and co-existence of covalent and metallic bonding characteristics.

A density-functional theory for (BAs)n clusters (n = 1–14): structures, stabilities and electronic properties

This paper investigates the lowest-energy structures, stabilities and electronic properties of (BAs)n clusters (n = 1–14) by means of the density-functional theory. The results show that the lowest-energy structures undergo a structural change from two-dimensional to three-dimensional when n = 4. With the increase of the cluster size (n ≥ 6), the (BAs)n clusters tend to adopt cage-like structures, which can be considered as being built from B2As2 and six-membered rings with B—As bond alternative arrangement. The binding energy per atom, second-order energy differences, vertical electron affinity and vertical ionization potential are calculated and discussed. The caculated HOMO—LUMO gaps reveal that the clusters have typical semiconductor characteristics. The analysis of partial density of states suggests that there are strong covalence and molecular characteristics in the clusters.

Structures and electronic properties of Mo2nNn (n=1−5): a density functional study

(Received 31 December 2009; revised manuscript received 30 August 2010) The lowest-energy structures and the electronic properties of Mo2nNn (n=1{5) clusters have been studied by using the density functional theory (DFT) simulating package DMol 3 in the generalized gradient approximation (GGA). The resulting equilibrium geometries show that the lowest-energy structures are dominated by central cores which correspond to the ground states of Mon (n = 2, 4, 6, 8, 10) clusters and nitrogen atoms which surround these cores. The average binding energy, the adiabatic electron a‐nity (AEA), the vertical electron a‐nity (VEA), the adiabatic ionization potential (AIP) and the vertical ionization potential (VIP) of Mo2nNn (n=1{5) clusters have been estimated. The HOMO{LUMO gaps reveal that the clusters have strong chemical activities. An analysis of Mulliken charge distribution shows that charge-transfer moves from Mo atoms to N atoms and increases with cluster size.

Appearance of metallic features in small tungsten clusters

The structures and properties of Wn (n = 2–14) clusters were studied by using the density functional theory (DFT) at LSDA level. The most stable structures of Wn (n = 2–14) clusters with global minimum were determined. The average binding energy (Eb), the first and second difference of total energy (ΔE, Δ2E), the vertical detachment energy (VDE), and the HOMO-LUMO gap versus the size were also discussed. The abrupt decrease of VDE and HOMO-LUMO gap at size n = 8 and 10 implied that tungsten clusters of W8 and W10 appeared to have metallic features. These changes were also accompanied by the delocalization of electron charge density and the strong hybridization between 5d and 6s orbits in W8 and W10 clusters. Our results are in good agreement with the available experimental data.