Density functional calculations of nickel, palladium and cadmium adsorption onto (10,0) single-walled carbon nanotube.

Adsorption of three heavy metals (Ni, Pd, Cd) onto (10,0) single-walled carbon nanotube (SWCNT) was investigated using density functional theory (DFT). Metals were adsorbed to both inside and outside of SWCNT and their structures and electronic properties [e.g., band structures and density of states (DOS)] were calculated and compared. The effects of substituting one carbon atom of the nanotube with these metals were also investigated. Formation energy results showed that adsorption inside and outside the nanotube is energetically favored. Significant changes were observed in the electronic properties of SWCNT after Ni and Pd adsorptions, and the nanotube changes from being a semi-conductor to a metallic conductor. However, the conductivity did not change markedly after Cd adsorption, indicating its physical adsorption to the nanotube. Spin polarized calculations showed that nickel adsorption inside and outside SWCNT induces magnetization of the system. Different electronic properties were obtained after adsorption of Pd atoms to different sides of SWCNT. Partial DOS were also applied to interpret the changes in electronic properties more precisely.

A DFT study of the structural and electronic properties of periodic forms of aniline and pyrrole polymers and aniline-pyrrole copolymer.

The structural and electronic properties of polyaniline, polypyrrole, and poly(aniline-co-pyrrole) (Ani-co-Py) in periodic form were investigated using calculations based on density functional theory (DFT). One to three monomers of aniline and pyrrole were placed in a supercell, and the effects of dihedral angles between the monomers on the electronic properties of the polymers were explored. All polymer configurations were optimized, and the band structures and densities of states (DOSs) were calculated and compared. The band gap of each polymer was calculated as the smallest energy difference between the HOMO and LUMO bands. The results showed that both sets of homopolymers exhibit semiconducting behavior which becomes less prominent after copolymerization. A comparison of the band structures of the homopolymers and the copolymer indicated that the pyrrole in the copolymer acts as an acceptor. The projected density of states (PDOS) was examined to obtain additional insight into orbital interactions and to identify the atoms that are most influential in the electronic properties of the studied polymers.