Structures and magnetic properties of transition metal （TM） Fe or Ni monoatomic chains （MACs） encapsulated by a Au （5, 5） nanotube （Fe@Au and Ni@Au） are investigated using the density functional theory （DFT）. The calculated results show that both Fe@Au and Ni@Au prefer to adopt ferromagnetic （FM） orders as ground states. In particular, the Fe@Au keeps the magnetic properties of free-standing Fe MAC, indicating that this system may be viewed as a new candidate in electromagnetic devices.
The structural, electronic, and optical absorption properties of TiO2 nanotube （TiO2NT） with Cun clusters （n =1-4） adsorbed on its surface have been investigated based on density functional theory calculations. The TiO2NT is constructed by rolling up a （101） sheet of anatase TiO2 around the [ 1-01 ] direction; the ground states of Cun/TiOzNT systems are determined by analyzing the average adsorption energies. Calculation results show that odd-even oscillations occur for the average adsorption energy, the Cu-O bond length, and the amount of transferred electrons, with the increase in Cu. cluster size; and the Cun/TiO2NTs with odd n＇s demonstrate stronger interaction between the Cu. cluster and the TiO2NT. Also, the impurity states introduced by the Cun cluster to the band gap of TiOzNT cause an obvious redshift of the optical absorption spectrum toward the visible light region, especially for the even n cases.
