We investigated the adsorption of diatomic molecules, CO, NO, and O 2 , denoted by XO on iron tapeporphyrin ͑FeTP͒ using first-principles calculations based on density functional theory. In this work, we present the structure and electronic properties of iron tape-porphyrin and its complexes with CO, NO, and O 2 . The binding of such diatomic molecules to FeTP gave rise to significant changes on both the geometric structure and electronic properties of FeTP. We found that in all FeTP complexes with diatomic molecules, the Fe atom moves out of the porphyrin plane toward the adsorbed molecule. The energy of the iron-diatomic molecule bond increases in the order of Fe-O 2 ͑0.554 eV͒ Ͻ Fe-CO ͑1.225 eV͒ Ͻ Fe-NO ͑1.719 eV͒. At its stable position, the Fe-X-O angle increases in the order of Fe-C-O Ͼ Fe-N-O Ͼ Fe-O-O. The changes in geometric structure are in accordance with other density functional theory calculations and experimental results for porphyrin molecule. As regards the electronic properties, there appears an energy gap between the conduction band and valence band in CO-adsorbed and NO-adsorbed cases with a more pronounced energy gap in the former, while none was observed in the O 2 -adsorbed case. We attribute these changes in electronic properties to the strong interaction involving the d orbitals of the Fe atom and the * orbitals of diatomic molecules. Specifically, for the CO and NO adsorbed on FeTP cases, the change in electronic properties is attributed to the strong hybridization of d xz and d yz orbitals of the Fe atom and * orbitals. For O 2 adsorbed on FeTP, the hybridization of the d z 2 orbital of the Fe atom and * orbitals plays the key role in O 2 -iron tape-porphyrin interaction.

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The behavior of a hydrogen atom on a Pd 3 Ag(111) surface is investigated by calculating the quantum states of the hydrogen atom via the first principles calculation methods. The calculation results show that the ground state wave function for the motion of hydrogen atom is localized on the fcc hollow site surrounded by three Pd atoms. Moreover, activation energies for the diffusion of the hydrogen atom on the whole Pd 3 Ag(111) surface are estimated as 394 and 520 meV via quantum and classical methods, respectively. Compared with our previous study on the behavior of hydrogen atom on the Pd(111) surface, the adsorption energy of hydrogen atom becomes smaller, while the activation energy becomes larger as a result of Ag alloying.

We have investigated the electronic properties of iron tape-porphyrin and its complex with NO. We found that at the stable position, Fe-N-O angle is about 148• . As regards the electronic properties, there appears an energy gap between conduction band and valence band. We attribute these changes in electronic properties to the strong interaction involving the d xz , d yz and d zz orbitals of the Fe atoms and the π * orbitals of NO molecule.

We have investigated the electronic and magnetic properties of ð3; 3Þ and ð4; 4Þ single-walled carbon nanotubes (SWNTs) filled with 3d transition metal (TM) monatomic chains, using first-principles calculations based on the density functional theory to get a thorough understanding of metal atom-filled carbon nanotubes. We have found that the magnetic moment of 3d TM-filled SWNTs decreases when the TM atom changes from smaller atomic radius to larger atomic radius or, when the diameter of the SWNT decreases. Specifically, the magnetic moment increases as the bonding strength between a TM atom and carbon atoms decreases.