Gaobin Liu

All-electron scalar relativistic calculation of water molecule adsorption onto small gold clusters

AbstractAn all-electron scalar relativistic calculation was performed on AunH2O (n = 1–13) clusters using density functional theory (DFT) with the generalized gradient approximation at PW91 level. The calculation results reveal that, after adsorption, the small gold cluster would like to bond with oxygen and the H2O molecule prefers to occupy the single fold coordination site. Reflecting the strong scalar relativistic effect, Aun geometries are distorted slightly but still maintain a planar structure. The Au–Au bond is strengthened and the H–O bond is weakened, as manifested by the shortening of the Au–Au bond-length and the lengthening of the H–O bond-length. The H–O–H bond angle becomes slightly larger. The enhancement of reactivity of the H2O molecule is obvious. The Au–O bond-lengths, adsorption energies, VIPs, HLGs, HOMO (LUMO) energy levels, charge transfers and the highest vibrational frequencies of the Au–O mode for AunH2O clusters exhibit an obvious odd-even oscillation. The most favorable adsorption between small gold clusters and the H2O molecule takes place when the H2O molecule is adsorbed onto an even-numbered Aun cluster and becomes an AunH2O cluster with an even number of valence electrons. The odd–even alteration of magnetic moments is observed in AunH2O clusters and may serve as material with a tunable code capacity of “0” and “1” by adsorbing a H2O molecule onto an odd or even-numbered small gold cluster. Lowest energy geometry for Au10H2O cluster. The average Au–Au, Au–O, and H–O bond-lengths (in Ångstrom) and the H–O–H bond angle are shown next to the clusterSize dependence of vertical ionization potentials (VIP), HOMO–LUMO gaps (HLG), highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) energy level for AunH2O clusters

A comparative study between all-electron scalar relativistic calculation and all-electron calculation on the adsorption of hydrogen molecule onto small gold clusters

AbstractA comparative study between all-electron relativistic (AER) calculation and all-electron (AE) calculation on the H2 molecule adsorption onto small gold clusters has been performed. Compared with the corresponding AunH2 cluster obtained by AE method, the AunH2 cluster obtained by AER method has much shorter Au–H bond-length, much longer H–H distance, larger binding energy and adsorption energy, higher vertical ionization potentials (VIP), greater charge transfer, higher vibrational frequency of Au–H mode and lower vibrational frequency of H–H mode. The delocalization of the highest occupied molecular orbital (HOMO) and the lowest unoccupied molecular orbital (LUMO) for AunH2 cluster obtained by AER method is obvious. All these characteristics suggest that the scalar relativistic effect might strengthen the Au–H bond and weaken the H–H bond. It is believed that the scalar relativistic effect is favourable to the H2 molecule adsorption onto small gold cluster and the reactivity enhancement of H2 molecule. It may be one of the reasons why the dissociative adsorptions take place in some AunH2 clusters. With increasing size of AunH2 clusters, the influence of scalar relativistic effect becomes more significant. Some further studies focused on the influence of scalar relativistic effect on the adsorption behaviour of other small molecules onto gold clusters are necessary in the future. Graphical AbstractThe adsorption energy of AunH2 cluster obtained by AER method is larger than those of AunH2 cluster obtained by AE method and previous work, indicating that the scalar relativistic effect might promote the adsorption of small gold cluster toward hydrogen molecule.

First-principles study on MRh12 (M = Rh, Fe, Co, AND Ni) clusters

In this paper, a first-principles study on the stability, electronic and magnetic properties of MRh12 (M = Rh, Fe, Co and Ni) clusters is performed. By optimizing the geometrical structure, we find that MRh12 clusters change from a perfect icosahedron to a distorted structure and have an obvious bond length contraction as compared with the corresponding bulk phase; FeRh12, CoRh12, and NiRh12 clusters are more energetically stable than the RhRh12 cluster. The effect of the impurity M on the density of states, valence band width, HOMO and LUMO for MRh12 clusters is not significant, but when the central Rh atom is substituted with M, the magnetic moment of MRh12 reduces dramatically. The Mulliken population analysis indicates that there are more charge transfers from other orbitals to Rh4d and M3d orbitals, and the spd hybrid effect in d orbitals of MRh12 clusters is stronger than that in the RhRh12 cluster. this situation means that the unpaired d electrons have more chance to be paired, and the magnetic moments of MRh12 clusters can be reduced reasonably.

A density functional theory study on the Ti/P binary cluster ions

Under the framework of density functional theory, an all-electron calculation on the geometrical structures and dissociation channels of Ti/P binary cluster ions has been carried out. The P2, P3 and P4 structures are found to be the relatively stable units in these cluster ions. The lowest energy geometries of these Ti/P binary cluster ions may be constructed by bonding Ti, Ti2, Ti3 or Ti4 unit with one or two relatively stable P2, P3 and P4 units. The most possible dissociation channels of these Ti/P binary cluster ions are the detachment of P2, P3 or P4 fragment. It is well consistent with the photodissociation experimental results.

All-electron scalar relativistic calculation of the adsorption of NCO species onto small copper clusters

An all-electron scalar relativistic calculation of CunNCO (n = 1–13) clusters has been made using density functional theory with the generalized gradient approximation at BLYP level. In all CunNCO clusters, the NCO species prefered to occupy the single-fold coordination site and the small copper cluster tended to bond with the nitric. The Cun structures were only distorted slightly and the NCO species retained linear structure. The N-C bond-length contraction and C-O bond-length elongation were observed clearly. The reactivity enhancement of NCO species toward CO2 was obvious. But, no reactivity enhancement of NCO to form N2 related to the N-C bond strength could be observed. It seems that the NCO species is more favorably adsorbed by odd-numbered small copper clusters, relatively. Some discrepancies between our work and earlier works were found which may be explained in terms of the scalar relativistic effect. Further studies to focus on the reactivity enhancement of NCO to form N2 are clearly in order.