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Bimetallic transition metal nanoclusters have attracted significant attention in recent years due to their wide range of applications such as heterogeneous catalysts, electrochemistry and alloy design. However many studies were reported on pure transition metal nanoclusters and bimetallic of late transition metal nanoclusters. In this study the density functional theory (DFT) with PBEsol exchange correlation functional was employed to investigate the structural and electronic properties of TiN-1Os (N = 2-16) nanoclusters. The calculations showed that osmium impurity mostly prefers to be encapsulated by titanium nanoclusters. The binding energies gradually decrease with the cluster size N. The Os dopant was found to enhance the binding energy of titanium nanoclusters. The relative stability or second order energies showed that Ti6Os and Ti12Os clusters are the most stable. Interestingly, osmium dopant converted the nanocluster with 13 atoms to be the most stable. Furthermore, the dissociation energy or first order energies showed an excellent correlation with the relative stability trend. The HOMO-LUMO revealed the lowest energy gap at Ti12Os (N = 13) which correlates well with the predicted binding energy, relative stability and dissociation energy.

Pyrolusite (β-MnO2) was investigated for potential use in energy storage devices due to its promising properties for cathode materials in rechargeable lithium-ion batteries. A combination of evolutionary algorithm search techniques and density functional theory techniques were used to determine the structural stabilities of the β-MnO2 nanoclusters on the energy landscape. However, pyrolusite suffers from some structural defects and impurities that hinder its optimal use. The predicted order of stability for the MnO2 nanoclusters correlates with isostructural TiO2. There is an improvement in the stability and electrical conductivity of the nanoclusters as compared to their β-MnO2 bulk counterparts. The cobalt doped nanoclusters showed a preference toward circular compact bonding patterns. The band-gap energy revealed that the nanoclusters have a metallic characteristic behaviour with narrow band gap energies, indicating their good conductive properties. Cobalt doping was shown to improve the structural properties of the nanoclusters based on the decreased bond lengths and more spherical bond angles. Moreover, it also succeeded in improving the conductivity of the nanoclusters based on the reduced Mulliken and Hirshfeld partial charges. The electronic charge density differences of the cobalt doped β-MnO2 nanoclusters displayed a prevalence of the weaker ionic bonding instead of the preferred stronger covalent bonding. This shows the limited effectiveness of cobalt as a dopant.

First-principles calculations were performed to determine the effect of Pt and Ru ternary alloying on structural, mechanical and dynamical properties of the binary Pm-3m-FeAl. FeAl based alloys are important for high-temperature applications due to their high oxygen corrosion resistance. Moreover, they are a major driver as a component for better infrastructure, industrial coating, and the improvement of automotive parts. The density functional theory (DFT) method within the generalized gradient approximation (GGA) approach was employed to perform all the calculations. The equilibrium cell parameters of the binary FeAl were predicted to be more than 90% in good agreement with the experimental data, warranting the validity of the approach employed. We found that Pt and Ru ternary alloying on FeAl significantly enhances the mechanical hardness, ductility and dynamical stability.

We have performed a genetic algorithm search on the tight-binding interatomic potential energy surface (PES) for small TiN (N = 2–32) clusters. The low energy candidate clusters were further refined using density functional theory (DFT) calculations with the PBEsol exchange–correlation functional and evaluated with the PBEsol0 hybrid functional. The resulting clusters were analysed in terms of their structural features, growth mechanism and surface area. The results suggest a growth mechanism that is based on forming coordination centres by interpenetrating icosahedra, icositetrahedra and Frank–Kasper polyhedra. We identify centres of coordination, which act as centres of bulk nucleation in medium sized clusters and determine the morphological features of the cluster. [ABSTRACT FROM AUTHOR]

Ab initio density functional theory was used to investigate the adsorption of oxygen molecule on the nickel-rich pentlandite (110) surface, which is important for mineral extraction. The three most reactive adsorption sites: Fe-top, Ni-top, and fcc-hollow have been considered. Firstly, the non-adsorbed pentlandite surface reflects the Ni atoms relaxing inwards. Consequently, their electronic structure showed high Fe 3d-orbital contribution than the Ni 3d-orbitals at the EF (indicating that the Fe atoms are more reactive than Ni). Secondly, the O²-adsorbed surface predicted lowest adsorption energy for Fe-top (-1.902 eV), as a more spontaneous reaction is likely to occur than on fcc-hollow (-1.891 eV) and Ni-top (-0.040 eV) sites, suggesting Fe preferential oxidation. The density of states indicates that the O² show prevalence of electrons in the πp* antibonding orbitals, and are reduced to zero states at the valence band on metal-bonded oxygen (O1). The σp* orbital is observed to reside just above the EF for Fe-top and fcc-hollow site, while on Ni-top is half-occupied for both metal-bonded oxygen (O1) and terminal oxygen (O²). Finally, the isosurface charge density difference showed electron (charge) depletion on Ni/Fe metals and accumulation on the O² molecule. Bader analysis indicated that the oxidized Fe and Ni atoms adopt more positive charge, while O² on Fe-top atoms possesses more negative charge than on Ni-top, resulting with O1 possessing a smaller charge than O2 atom. [ABSTRACT FROM AUTHOR]

We have performed a genetic algorithm search on the tight-binding interatomic potential energy surface (PES) for small TiN (N = 2-32) clusters. The low energy candidate clusters were further refined using density functional theory (DFT) calculations with the PBEsol exchange-correlation functional and evaluated with the PBEsol0 hybrid functional. The resulting clusters were analysed in terms of their structural features, growth mechanism and surface area. The results suggest a growth mechanism that is based on forming coordination centres by interpenetrating icosahedra, icositetrahedra and Frank-Kasper polyhedra. We identify centres of coordination, which act as centres of bulk nucleation in medium sized clusters and determine the morphological features of the cluster.