We systematically study the electronic properties of two-dimensional group-V materials, i.e. phosphorene, arsenene, antimonene, and bismuthene. The density functional calculations are performed using generalized gradient approximation. We first clarify that the α structure is the most stable in the cases of phosphorene and bismuthene and the β structure is the most stable in the cases of arsenene and antimonene. We next analyze the band structures based on group theory. As a result, we find that all the bands are doubly degenerated at the boundaries of the first Brillouin zone in the α structures and the degeneracies are due to the symmetry of the materials. The band gaps of the β structures are found to be larger than those of the α structures. This tendency in the band gaps is explained based on the fact that the band gap increases as the sp hybridization becomes large. We find that buckling occurs in the α structures of antimonene and bismuthene due to the electron transfer from the higher atom to the lower atom.

We systematically study geometries and band structures of two-dimensional group-V bilayer materials, i.e. phosphorene, arsenene and antimonene. Among the four stacking structures (AA, AB, AC, and AD), the AB stacking structures are found to be the largest band gaps and to be the most energetically stable. We find novel band structures on the whole Brillouin zone edges: four bands have close energies and two of the four bands have the same energy in many cases. We analyze the characteristic features of the band structures based on the group theory and clarify that the features depend on the space group of each stacking structure. We also find that the band splits due to the interlayer interaction is very small and this interaction becomes large as atoms become heavy.

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We perform density functional theory (DFT) study of CO 2 adsorption on graphene supported Ni catalyst. We implement ordinary PBE functional as well as van der Waals density functional (vdW-DF) to accommodate weakly interaction between CO 2 and graphene. Based on vdW-DF calculations, we obtained that CO 2 is physisorbed on pristine graphene, in contradiction with PBE results. The adsorption energy further increases when we introduce single Ni adatom and small Ni cluster on graphene. The adsorbed CO 2 bond angle and bond length on graphene with single Ni adatom and cluster are deformed from its gas phase condition, indicating that CO 2 is chemically adsorbed on the decorated graphene area. Our results provide useful insight into appropriate design of graphene supported metal catalysts.

Contrary to its name, the "lead" in pencil is predominately made up of combination of graphite and clay or polymer, hence it can be considered as carbon composite. It has been proven that the more amount of carbon, the greater Young Modulus will increase and vice versa. Some researches on electric property of carbon composite also have shown that pencil drawn can be treated as a strain gauges and chemiresistors on paper. It means that in pencil's lead, the mechanical and electrical properties are related to one another. In this study, we applied a compressive load on pencil's lead and measured the effect on its resistivity. The results show that the resistivity will decrease while the strain will increase.