Search

Bimetallic clusters have received extensive attention due to the changes in their properties and structures. Therefore, the structure and electronic configuration of medium-size Sr-doped magnesium clusters were studied in this work. The CALYPSO (crystal structure analysis by particle swarm optimization) algorithm and DFT (density functional theory) were applied to search, correct energy, and optimize geometry for stable low-energy structures. We described the structural evolution and characteristics of SrmMgn0/− (m = 1,2; n = 10–15) clusters, and found that a few ground-state isomers can maintain the same structure framework as the corresponding pure magnesium clusters. Through relative stability analysis, the SrMg13− cluster with a pyramid shape and Sr2Mg11 cluster with a pagoda-like shape were determined to be the most stable structures. Further analysis of the molecular orbitals and bonding characteristics of SrMg13− and Sr2Mg11 clusters also revealed a strong interaction between Sr and Mg atoms and the s–p bonding of Mg–Mg, which may be the main reason for the high stability of these clusters. We hope that this study will provide guidance for future doping of pure magnesium clusters. [ABSTRACT FROM AUTHOR]

• The evolution of the structures for Mg 2 Bn0/– (n = 1–12) clusters has be elucidated. • The corresponding ground state structures are determined. • The local stable ground state structure is found. • The properties of electrons and bonds of the most stable isomers are discussed. In this paper, a global search for the lowest energy structure of Mg 2 B n 0/- (n = 1–12) clusters is performed based on Density functional theory combined with the particle swarm optimization algorithm program CALYPSO. The geometry, stability, charge transfer, and bonding properties of the clusters were analyzed at the B3LYP/def2-tzvp level. Then Mg 2 B 8 with high symmetry D 4h was found to be the magic numbers cluster among them. The doped clusters Mg 2 B n 0/− were compared with the pure boron clusters B n+2 0/− (n = 1–12) at the same level. The following results are obtained: as the number of boron atoms increases, the boron clusters doped with Mg atoms change from a two-dimensional planar or quasi-plane structure to a three-dimensional structure. The doped magnesium atoms are always positively charged in the convex capped position. And the doping of Mg atoms drives the overall stabilization of the boron clusters and makes the clusters more compact. There is a large amount of charge transfer between the Mg atom and the B atom, and the main orbitals involved are the S and p orbitals. There are strong interactions between the two atoms of boron and magnesium. Through the analysis of the bonding properties, it was found that the s-p hybridization mode between Mg B is the main reason for the enhanced cluster stability. [Display omitted] [ABSTRACT FROM AUTHOR]

Using a newly developed particle swarm optimisation technique on crystal structural prediction, we have predicted an orthorhombicImm2 structure for TcN crystal, which is energetically much superior to the previously proposed NbO-type andR-3mstructures. The new phase is stable against decomposition into the mixture of Tc and N at ambient condition. The stability is confirmed by the subsequent calculations on the phonon dispersion curves and elastic constants. An analysis of the mechanical properties indicates thatImm2-TcN is incompressible and common hard material. The evidence of strong covalent bonding of Tc-N, which plays a leading role to form a hard material, is manifested by the partial densities of state analysis. In addition, the thermodynamic properties, such as Debye temperature, heat capacity, thermal expansion coefficient, and Grüneisen parameter of TcN are investigated by the quasi-harmonic Debye model. [ABSTRACT FROM PUBLISHER]

Here we reported the structures, electronic, spectral and thermodynamic properties of MB n −(M = La, Ce, Pr; n = 8, 9) clusters using Crystal structure Analysis by Particle Swarm Optimization (CALYPSO) searching method and density functional theory (DFT). Results found that the lowest structures of MB n −(M = La, Ce, Pr; n = 8, 9) possess the half-sandwich structure with C s symmetry, respectively. Based on the lowest energy structures, the electronic properties are analyzed by calculating charge transfer, electron localization function and polarizability; the photoelectron spectra, infrared spectra, Raman spectra and UV-vis spectra are computationally simulated to facilitate their spectral characterizations. At last, thermodynamic properties are symmetrically investigated for doped systems. We believe that our research will provide useful motivation for further experimental and theoretical investigations of lanthanide-doped boron based nanomaterials. [ABSTRACT FROM AUTHOR]