Ming-Min Zhong

Theoretical search for potential candidates as building blocks of hyperhalogens: BS2 and CrO4 molecules

Previous works have shown that hyperhalogens can be created by changing the building blocks from halogens to superhalogens, e.g. hyperhalogens (Cu(BO2)2, Na(BO2)2 and Au(BO2)2) are created by replacing halogens of superhalogens MX2 (M = Cu, Na and Au; X = F, Cl and Br) with the superhalogen BO2, which has a higher electron affinity of 4.46 eV. Thus we explore the possibility of creating new hyperhalogens by using BS2 and CrO4 as building blocks. Our results show that although both BS2 and CrO4 are superhalogens, just as BO2 is, among their dimers only (CrO4)2 is a superhalogen, while (BS2)2 is not. When a Au atom is decorated with BO2, BS2 or CrO4, we found that Au(BO2)2 and Au(BS2)2 clusters can be termed hyperhalogens as their respective EA is larger than their corresponding building block BO2 and BS2, while Au(CrO4)2 is not. This is because the extra electron charge mostly goes to high electronegative BO2 and BS2 in anionic Au(BO2)2 and Au(BS2)2 clusters, while in anionic Au(CrO4)2 the extra charge is primarily located on the Au site. Moreover, the study of the interaction of superhalogen BS2 with Li or K atoms further confirms the ability of BS2 to act as a building block for hyperhalogens. The calculated fragmentation energies indicate that all of the clusters are stable against any fragmentation.

Probing the structural and electronic properties of aluminum-sulfur Al n S m (2 ≤ n + m ≤ 6) clusters and their oxides

Using the first-principle density functional calculations, the equilibrium geometries and electronic properties of anionic and neutral aluminum-sulfur AlnSm (2 ≤ n + m ≤ 6) clusters have been systematically investigated at B3PW91 level. The optimized results indicate that the lowest-energy structures of the anionic and neutral AlnSm clusters prefer the low spin multiplicities (singlet or doublet) except the Al2‾, Al2, S2, Al4 and Al2S4 clusters. A significant odd-even oscillation of the highest occupied-lowest unoccupied molecular orbital (HOMO-LUMO) energy gaps for the AlnSm‾ clusters is observed. Electron detachment energies (both vertical and adiabatic) are discussed and compared with the photoelectron spectra observations. Furthermore, a good agreement between experimental and theoretical results gives confidence in the most stable clusters considered in the present study and validates the chosen computational method. In addition, the variation trend of chemical hardness is in keeping with that of HOMO-LUMO energy gaps for the AlnSm clusters. Upon the interaction of oxygen with the stable AlSm‾ clusters, the dissociative chemisorptions are favorable in energy. The binding energy and Gibbs free energy change show completely opposite oscillating behaviors as the cluster size increases.

Evolution of geometrical structures, stabilities and electronic properties of neutral and anionic Li n Cu λ (n = 1–9, λ = 0, −1) clusters: compare with pure lithium clusters

The structural evolution, stabilities, and electronic properties of copper-doped lithium Li n Cuλ (n = 1–9, λ = 0, −1) clusters have been systematically investigated using a density functional method at PW91PW91 level. Extensive searches for ground-state structures were carried out, and the results showed the copper tends to occupy the most highly coordinated position and form the largest probable number of bonds with lithium atoms. By calculating the binding energies per atom, fragmentation energies and the HOMO-LOMO gaps, we found LiCu, Li7Cu, LiCu−, Li2Cu− and Li8Cu− clusters have the stronger relative stability and enhanced chemical stability. The content and pattern of frontier MOs for the most stable doped isomers were analysed to investigate the bond nature of interaction among Li and Cu atoms. The results show some σ-type and π-type bonds are formed among them, and with small admixture of the Cu d characters. To achieve a deep insight into the electron localization and reliable electronic structure information, the natural population analysis and electron localization function were performed and discussed.

Density functional study of the structural and electronic properties of tetra-aluminum oxide image omitted (3 n 8,=0,-1) clusters

The geometric structures, relative stabilities, and electronic properties of a series of tetra-aluminum oxide clusters, ( , ), were systematically investigated using density functional theory calculations at the B3LYP level. The optimized geometries reveal a structural transition from a two-dimensional to a three-dimensional structure for n ≤5 for the neutral species, but the three-dimensional structures are preferable for all negative clusters with the exception of . The dissociation energy, the second difference energy and the highest occupied–lowest unoccupied molecular orbital gaps as a function of the cluster size exhibit a significant even–odd alternation phenomenon. It is found that the neutral cluster is relatively stable and exhibits strong chemical stability. Furthermore, the calculated (vertical and adiabatic) electron detachment energies are also compared with previous experimental data obtained from photoelectron spectra.

Probing the structural, electronic and magnetic properties of multicenter Fe2S2 0/−, Fe3S4 0/− and Fe4S4 0/− clusters

The structural, electronic and magnetic properties of neutral and anion Fe2S2, Fe3S4 and Fe4S4 have been investigated with the aid of previous photoelectron spectroscopy and density functional theory calculations. Theoretical electron detachment energies (both vertical and adiabatic) of anion clusters for the lowest energy structure were computed and compared with the experimental results to verify the ground states. The optimized structures show that the ground state structures of Fe2S20/−, Fe3S40/− and Fe4S40/− favor high spin state and are similar to their structures in proteins. The electron delocalization pattern for all the clusters and the nature of bonding between Fe and S atoms were studied by analyzing molecular orbitals. Natural population analysis demonstrates that Fe atoms act as an electron donor in all clusters, and the electron density difference map clearly shows the direction of the electron flow over the whole complex. Furthermore, the investigated magnetism shows that the Fe atoms carried most of the magnetic moments, which is due mainly to the 3d state, while only very small magnetic moments are found on S atoms.

Probing the structural and electronic properties of small aluminum dideuteride clusters.

Adsorption of deuterium on the neutral and anionic Aln(λ) (n=1-9, 13; λ=0, -1) clusters has been investigated systematically using density functional theory. The comparisons between the Franck-Condon factor simulated spectra and the measured photoelectron spectroscopy (PES) of Cui and co-workers help to search for the ground-state structures. The results showed that D2 molecule tends to be dissociated on aluminum clusters and forms the radial AlD bond with one aluminum atom. By studying the evolution of the binding energies, second difference energies and HOMO-LUMO gaps as a function of cluster size, we found Al2D2, Al6D2 and Al7D2(̄) clusters have the stronger relative stability and enhanced chemical stability. Also, considering the larger adsorption energies of these three clusters, we surmised that Al2, Al6 and Al7(̄) may be the better candidates for dissociative adsorption of D2 molecule among the clusters we studied. Furthermore, the natural population analysis (NPA) and difference electron density were performed and discussed to probe into the localization of the charges and reliable charge-transfer information in AlnD2 and AlnD2(̄) clusters.

Interdot Coulomb correlation effects and spin-orbit coupling in two carbon nanotube quantum dots

Transport properties of the two-level Kondo effect involving spin, orbital, and pseudospin degrees of freedom are examined in a parallel carbon nanotube double quantum dot with a sufficient interdot Coulomb interaction and small interdot tunneling. The interdot Coulomb correlation effects are taken into account, and it plays an important role in forming bonding and antibonding states. Attached to ferromagnetic leads, the Kondo effect is observed at the interdot Coulomb blockade region with degeneracy of spin, orbital, and pseudospin degrees of freedom. A crossover from a two-level Kondo state involving the fivefold degeneracy of the double quantum dots to an SU(4) spin-orbit Kondo state and to an SU(2) spin-Kondo effect is demonstrated. At finite magnetic field, the splitting of the spin, orbital, and pseudospin Kondo resonance can be restored. For finite intradot Coulomb interaction U, there is a competition between the single-dot Kondo effect and the antiferromagnetic exchange coupling JAFM, resulting i...

Topological phase transition and gate-controlled charge transfer in minimal topological-spin qubit circuit

We propose a minimal topological-spin qubit circuit to investigate the non-Abelian rotations within the degenerate ground-state manifold, as well as the topological phase transition and charge transfer. From a quantum dot, the state of the Majorana system can be read out. Along with the splitting of the degenerate ground-state manifold of a topological qubit, a topological phase transition is observed, showing the existence of a Majorana fermion. By choosing the phase difference across the dots, the non-Abelian rotations and the required energetically degenerate state in the qubit can be achieved, which results in universal quantum computation. Moreover, on the basis of the measurement of the electron in quantum dots and topological qubit, this demonstrates that topologically protected tunnel braids between dots and MBSs are critical to non-Abelian rotations.