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Structural, Elastic, and Electronic Properties of ReB2: A First-Principles Calculation

The structural, elastic, and electronic properties of the hard material ReB2 have been investigated by means of density functional theory. The calculated equilibrium structural parameters of ReB2 are in agreement with the experimental results. Our result of bulk modulus shows that it is a low compressible material. Furthermore, the elastic anisotropy is discussed by investigating the elastic stiffness constants. The charge density and the electronic properties indicate that the covalent bonding of Re-B and B-B plays an important role in formation of a hard material. The good metallicity and hardness of ReB2 might serve as hard conductors.

First principles studies for formation mechanism and properties of ethylene molecule adsorbing on diamond (100) surface

We employed density functional theory within the generalized gradient approximation to investigate the diamond (100) surface, with hydrogen and ethylene terminations. The radical chain reaction is investigated by slab models, and two possible adsorption ways are found according to our calculations. In addition, the electron affinity of H-terminated diamond is also calculated, which indicates that the existence of negative electron affinity of H-C (100) surface provides a necessary condition for initiating radical chain reaction. Our results also imply that ethylene molecules can form strong C-C covalent bonds with diamond surface, which make it more resistant against degradation processes. Furthermore, according to the analysis of electronic structures, we have found localized gap state above the valence band, which is mainly contributed by the interaction between diamond surface and ethylene molecule and can weaken the surface conductivity of the adsorbed diamond.

Native defects and impurities in Zn3 N2: first-principle studies using gradient-correction approximation

First-principle density-functional calculations were performed to investigate the electronic structures, atomic structures and formation energies for native defects, oxygen impurities and related complexes in Zn3N2. The formation energy calculated shows that the configurations of substitutional O for N and O plus a N vacancy complex (ON(1)–VN(2)) are energetically favorable in both N-rich and Zn-rich growth conditions. The electronic structures demonstrate that N vacancy, substitutional O, and ON(1)–VN(2) complex defective Zn3 N2 are of n-type conduction character.

Theoretical Study of Differences between Surface and Bulk Electronic States in Cu Clusters

The size-dependent electronic structures of metal clusters Cun (n=2-20) have been calculated using density functional theory method. The results reveal that their electronic properties are almost the same as bulk material if the cluster size larger than a critical value. The properties can be understood by a surface-noncrystalline-layer model that composed of an interior crystalline-like core and an outer surface noncrystalline layer.

FERMI-ENERGY AND MINIMUM DIAMETER FOR METALLIC SILVER CLUSTER

The Fermi energy and the minimum size for silver (Ag) metallic clusters have been investigated by the electronic structure calculations using density functional theory method. The results reveal that the work function of clusters with metallicity has the same value as that of bulk metals. This result is interpreted by the role of localized surface states in a thin layer and furthermore it is deduced that a nonmetal layer exists at the surface of Ag bulk metals and their clusters. This layer-thickness is about the same as the lattice constant and the minimum diameter for metallic clusters is about twice of the layer-thickness.