Adsorption and desorption of an oxygen molecule on carbon nanotubes are investigated using density functional calculations. Several precursor states exist at the edge of armchair nanotubes, whereas an exothermic adsorption takes place at the edge of zigzag nanotubes. We also estimate desorption barriers of a CO molecule from nanotubes as well as fullerenes and amorphous phases. Our calculations suggest that carbon nanotubes can survive selectively during the oxidative etching process with a precise control of annealing temperature, in good agreement with experimental results of purification process of carbon nanotubes.
We investigate atomic and electronic structures of the threading edge dislocations of GaN using selfconsistent-charge density-functional tight-binding approaches. Full-core, open-core, Ga-vacancy, and N-vacancy edge dislocations are fully relaxed in our total-energy scheme. The Ga-vacancy dislocation is the most stable in a wide range of Ga chemical potentials, whereas full-core and open-core dislocations are more stable than others in the Ga-rich region. Partial dehybridization takes place during the lattice relaxation near the dislocation in all cases. The dangling bonds at Ga atoms mostly contribute to the deep-gap states, whereas those at N atoms contribute to the valence-band tails. All the edge dislocations can act as deep trap centers, except the Ga-vacancy dislocation, which may act as an origin of yellow luminescence.
The
applications of the novel anion-functionalized protic ionic
liquid (ILs), prepared from superbase 1,8-diazabicyclo[5.4.0]undec-7-ene
(DBU) with imidazole, in the CO2 absorption have been investigated.
It has been detected that this ionic liquid can reversibly capture
about 1 mol of CO2 per mole ionic liquid. In addition,
the influence of temperature, pressure, water, and substituent of
anions has been uncovered. The capture of CO2 was significantly
affected by the substituents in imidazole-based anion, suggesting
that electric-charge distribution in imidazole ring system can play
an important role in determining the reaction of ILs with CO2.
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