The epoxidation of different bonds with the same bond curvature in one nanotube including armchair, zigzag and chiral tubes was studied. The calculated results showed that for the adducts with opened C-O--C configuration, the magnitude of the binding energies was related with their corresponding bonding characteristics in HOMO, and the larger binding energies were attributed to stronger orbital interaction between one O atom and the nanotube; whereas for the adducts with 3MR structures, the binding energies were related with the changes of C-C bond length and independent of the frontier orbital interaction before and after epoxidation.
The absorption and emission spectra of the wurtzite Mn-doped GaN were calculated with cluster models.The predicted lattice parameters become slightly larger than those of undoped cluster.The average bond length of Mn–N is longer than that of Ga–N.Spin density shows that one Mn atom in these clusters has four single electrons with the same direction of the spin polarity.The new energy level with light Mn-doping appears at 1.37 eV above the valance band.The absorption spectra of Mn-doped GaN cover the visible light region.The calculated emission spectra show that the green luminescence of GaN material in experiment did not result from Mn dopant.With the increase of Mn doping,the emission intensity of yellow or blue band increases to different extent and the band-to-band emission band shows red shift from peak at 3.34 to 3.24 eV.
The adsorption and reaction of O ＋ CN → OCN on Cu（100） are studied by using density functional theory and cluster model. Cu14 cluster model is used to simulate the surface. The calculated results show that the OCN species with the molecule perpendicular to the surface via N atom （N-down） is more favorable than other adsorption models, and the N-down at the bridge site is the most favorable. For N-down, calculated OCN symmetric and asymmetric stretching frequencies are all blue-shifted compared with the calculated values of free and in good agreement with the experiments. The charge transfer from the surface to the OCN species leads to that the bonding of OCN to the metal surface is largely ionic. The present studies also show that CN with the molecule perpendicular to the surface via C atom （NC-down） at the top site is the most stable. Except NC-down at the top site, the calculated CN stretching frequencies are all red-shifted. With O coadsorbed at the hollow site, the adsorption of NC-down at the next nearest bridge or top site is energetically more favorable than that at the adjacent hollow site. The reaction of O ＋ CN → OCN on Cu（100） has no energy barrier via both Eley-Rideal and Langmuir-Hinshelwood processes.
