Ya-Ru Zhao

Equilibrium Geometries, Stabilities, and Electronic Properties of the Bimetallic M2-doped Aun (M = Ag, Cu; n = 1−10) Clusters: Comparison with Pure Gold Clusters

The density functional method with relativistic effective core potential has been employed to investigate systematically the geometrical structures, relative stabilities, growth-pattern behaviors, and electronic properties of small bimetallic M(2)Au(n) (M = Ag, Cu; n = 1-10) and pure gold Au(n) (n ≤ 12) clusters. The optimized geometries reveal that M(2) substituted Au(n+2) clusters and one Au atom capped M(2)Au(n-1) structures are dominant growth patterns of the stable alloyed M(2)Au(n) clusters. The calculated averaged atomic binding energies, fragmentation energies, and the second-order difference of energies as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. The analytic results exhibit that the planar structure Ag(2)Au(4) and Cu(2)Au(2) isomers are the most stable geometries of Ag(2)Au(n) and Cu(2)Au(n) clusters, respectively. In addition, the HOMO-LUMO gaps, charge transfers, chemical hardnesses and polarizabilities have been analyzed and compared further.

Geometries, Stabilities, and Electronic Properties of Small Anion Mg-Doped Gold Clusters: A Density Functional Theory Study

First-principle density functional theory is used for studying the anion gold clusters doped with magnesium atom. By performing geometry optimizations, the equilibrium geometries, relative stabilities, and electronic and magnetic properties of [Au(n)Mg]⁻ (n = 1-8) clusters have been investigated systematically in comparison with pure gold clusters. The results show that doping with a single Mg atom dramatically affects the geometries of the ground-state Au(n+1)⁻ clusters for n = 2-7. Here, the relative stabilities are investigated in terms of the calculated fragmentation energies, second-order difference of energies, and highest occupied−lowest unoccupied molecular orbital energy gaps, manifesting that the ground-state [Au(n)Mg]⁻ and Au(n+1)⁻ clusters with odd-number gold atoms have a higher relative stability. In particular, it should be noted that the [Au₃Mg]⁻ cluster has the most enhanced chemical stability. The natural population analysis reveals that the charges in [Au(n)Mg]⁻ (n = 2-8) clusters transfer from the Mg atom to the Au frames. In addition, the total magnetic moments of [Au(n)Mg]⁻ clusters exhibit an odd-even oscillation as a function of cluster size, and the magnetic effects mainly come from the Au atoms.

Structural, electronic and magnetic properties of gold cluster doped with calcium: Au(n)Ca (n=1-8)

The geometrical structures, relative stabilities, electronic and magnetic properties of calcium-doped gold clusters Au n Ca (n = 1–8) have been systematically investigated by employing density functional method at the BP86 level. The optimised geometries show that the ground-state structures are planar structures for Au n Ca (n = 3–8) clusters. Ca-substituted Au n +1 clusters, as well as Au-capped Au n −1Ca clusters, are dominant growth patterns for the Au n Ca clusters. The relative stabilities of Au n Ca clusters for the ground-state structures are analysed based on the averaged binding energies, fragmentation energies and second-order difference of energies. The calculated results reveal that the Au2Ca isomer is the most stable structure for small size Au n Ca (n = 1–8) clusters. The HOMO-LUMO energy gaps as a function of the cluster size exhibit a pronounced even–odd alternation phenomenon. Subsequently, charge transfers and magnetic moment of Au n Ca (n = 1–8) clusters have been analysed further.

Ab initio calculation of the geometries, stabilities, and electronic properties for the bimetallic Be2Au(n) (n = 1-9) clusters: comparison with pure gold clusters.

Ab initio methods based on density functional theory at BP86 level were applied to the study of the geometrical structures, relative stabilities, and electronic properties of small bimetallic Be2Aun (n = 1–9) clusters. The optimized geometries reveal that the most stable isomers have 3D structures at n = 3, 5, 7, 8, and 9. Here, the relative stabilities were investigated in terms of the averaged atomic binding energies, fragmentation energies and second-order difference of energies. The results show that the planar Be2Au4 structure is the most stable structure for Be2Aun clusters. The HOMO−LUMO gap, vertical ionization potential, vertical electron affinity and chemical hardness exhibit a pronounced even–odd alternating phenomenon. In addition, charge transfer and natural electron configuration were analyzed and compared.

First-principles studies of the electronic and dynamical properties of monosilicides MSi (M = Fe, Ru, Os)

We study the electronic band structure, dielectric, and lattice dynamical properties of FeSi, RuSi and OsSi from first principles using density functional theory. We performed the band structure calculations for these compounds to confirm they are indirect band-gap semiconductors. Density functional perturbation theory is employed to evaluate the Born effective charge tensors, the dielectric permittivity tensors, the phonon frequencies at the Γ-point, and the phonon dispersion curves as well as the corresponding density of states. These calculated results are in reasonable agreement with the experimental data and theoretical values available. From the present calculation we also predict that there exist longitudinal-transverse optical (LO-TO) splittings by 2–32 cm- 1 for these three compounds, which were not observed in previous experiments.

Equilibrium geometries, stabilities, and electronic properties of the cationic AunBe+ (n=1-8) clusters: comparison with pure gold clusters

Ab initio method based on density functional theory at PW91PW91 level has been applied in studying the geometrical structures, relative stabilities, and electronic properties of small bimetallic AunBe+ (n = 1–8) cluster cations. The geometrical optimizations indicate that a transition point from preferentially planar (two-dimensional) to three-dimensional (3D) structures occurs at n = 6. The relative stabilities of AunBe+ clusters for the ground-state structures are analyzed based on the averaged binding energies, fragmentation energies, and second-order difference of energies. The calculated results reveal that the AuBe+ and Au5Be+ clusters possess higher relative stability for small size AunBe+ (n = 1–8) clusters. The HOMO-LUMO energy gaps as a function of the cluster size exhibit a pronounced even-odd alternation phenomenon. Sequently, the natural population analysis and polarizability for our systems have been analyzed and compared further.

A systematic search for the structures, stabilities, and electronic properties of bimetallic Ca 2 -doped gold clusters: comparison with pure gold clusters

The local meta-GGA exchange correlation density functional (TPSS) with a relativistic effective core potential was employed to systematically investigate the geometric structures, stabilities, and electronic properties of bimetallic Ca2Aun (n = 1–9) and pure gold Aun (n ≤ 11) clusters. The optimized geometries show that the most stable isomers for Ca2Aun clusters have 3D structure when n > 2, and that one Au atom capping the Ca2Aun−1 structure for different-sized Ca2Aun (n = 1–9) clusters is the dominant growth pattern. The average atomic binding energies and second-order difference in energies show that the Ca2Au4 isomer is the most stable among the Ca2Aun clusters. The same pronounced even–odd alternations are found in the HOMO–LUMO gaps, VIPs, and hardnesses. The polarizabilities of the Ca2Aun clusters show an obvious local minimum at n = 4. Moreover, the inverse corrections to the polarizabilities versus the ionization potential and hardness were found for the gold clusters.

Structural and electronic properties of silver-doped gold clusters Au n Ag v (2 ≤ n ≤ 10; v = 0, ±1): comparison with pure gold clusters

The structural and electronic properties of silver-doped gold clusters Au n Ag v (2 ≤ n ≤ 10; v = 0, ±1) have been systematically investigated using density functional theory. The results show that the ground state optimal structures of the cationic and neutral clusters are found to be planar up to n = 3 and 9, respectively. However, for the anionic clusters, no three-dimensional lowest-energy structures are obtained according to DFT calculations. The calculated binding energy and dissociation energy as a function of cluster size exhibit odd–even alternations. The natural population analysis indicates that in Au n Ag v clusters charges transfer from the Ag atom to the Au frames. The trends for the vertical detachment energies, adiabatic electron affinities, adiabatic ionization potentials, and chemical hardness of Au n Ag v clusters, as the cluster size increases, are studied in detail and compared with the available experimental data.

Theoretical investigation on the high-pressure structural transition and thermodynamic properties of cadmium oxide

A theoretical investigation on the structural and thermodynamic properties of CdO under high pressure is performed by employing the pseudopotential plane-wave method in the framework of the density functional theory. Some structural parameters of CdO in both B1 and B2 phases are reported. According to the third-order Birch-Murnaghan equation of states, the transition pressure P(t) of CdO from the B1 structure to the B2 structure is determined. The calculated results are found to be in good agreement with the available experimental data and theoretical values. Based on the quasi-harmonic Debye model, the Debye temperature of CdO under high pressure is derived from the average sound velocity. This is a quantitative theoretical prediction of the elastic and thermodynamic properties of CdO and it still awaits experimental confirmation. Copyright (C) EPLA, 2010

A DFT study on equilibrium geometries, stabilities, and electronic properties of small bimetallic Na-doped Au(n) (n = 1-9) clusters: comparison with pure gold clusters.

A systematic study on the geometric structures, relative stabilities, and electronic properties of small bimetallic AunNa (n = 1-9) clusters has been performed by means of first-principle density functional theory calculations at the PW91PW91 level. The results show that the optimized ground-state isomers adopt planar structures up to n = 5, and the Na-capped geometries are dominant growth patterns for n = 6-9. Dramatic odd-even alternative behaviors are obtained in the second-order difference of energies, fragmentation energies, highest occupied-lowest unoccupied molecular orbital energy gaps, and chemical hardness for both AunNa and Aun+1 clusters. It is found that Au5Na and Au6 have the most enhanced stability. Here, the size evolutions of the theoretical ionization potentials are in agreement with available experimental data, suggesting a good prediction of the lowest energy structures in the present study. In addition, the charge transfer has been analyzed on the basis of natural population analysis.