Effect of preparation and reaction conditions on the performance of In/H-Beta for selective catalytic reduction of NOx with CH4.

In/H-Beta catalyst was prepared by optimizing the support, concentration of ion exchange liquid and calcination temperature to investigate the effects of synthesis conditions on catalytic activity of selective catalytic reduction of NOx with CH4. The results showed that the In/H-Beta catalyst exhibited the superior activity when concentration of exchange liquid was 0.033 M and calcination temperature was 500 °C, the NOx removal ratio could reach 97.6%. In addition, reaction conditions could affect the catalytic performance. When O2 concentration was 10%, CH4:NO ratio was no less than one, space velocity was lower than 23600 h-1 and NO initial concentration was no more than 700 ppm, In/H-Beta could exhibit superior catalytic activity. Moreover, the catalytic performances of In/H-Beta catalysts were discussed after enduring H2O or/and SO2. This novel strategy could open the door for selective catalytic reduction of NOx with CH4.

Conductive path formation in the Ta2O5 atomic switch: first-principles analyses.

The conductive path formed by the interstitial Cu or oxygen vacancies in the Ta(2)O(5) atomic switch were investigated in detail by first-principles methods. The calculated results indicated that the defect state induced by the interstitial Cu is located just at the Fermi level of the Cu and Pt electrodes in the Cu/Ta(2)O(5)/Pt heterostructure and that a conduction channel is formed in the Ta(2)O(5) film via the interstitial Cu. On the other hand, oxygen vacancies in Ta(2)O(5) do not form such a conduction channel because of the lower energy positions of their defect states. The above results suggest that the conductive path could be formed by interstitial Cu in the Ta(2)O(5) atomic switch, whereas the oxygen vacancies do not contribute to the formation of the conductive path.

The complex structure of liquid Cu(6)Sn(5) alloy.

By applying ab initio molecular dynamics simulation to liquid Cu(6)Sn(5) alloy, the hetero-coordination tendency is discovered by Bathia-Thornton partial correlation functions and a chemical short-range parameter. However the local structural environment of Sn in l-Cu(6)Sn(5) alloy resembles that of liquid Sn by Voronoi analysis. A new feature, i.e. a subpeak in between the first and second peaks, is discovered by the present method which implies that topologically disordered ß-Sn-type structural units may exist in l-Cu(6)Sn(5) alloy. The local density states of electrons show that both Cu-Sn and Sn-Sn bonding exist in l-Cu(6)Sn(5) alloy. This work suggests that chemical short-range order between unlike atoms and self-coordination between Sn atoms coexists in l-Cu(6)Sn(5) alloy.

Migration of Ag in low-temperature Ag2S from first principles.

Using the density-functional theory combined with the nudged elastic band method, we have calculated migration pathways and estimated the activation energy barriers for the diffusion of Ag ions in low-temperature Ag2S. The activation energy barriers for four essential migrations for an Ag ion, namely, from a tetrahedral (T) site to an adjacent T vacancy (VT), from an octahedral (O) site to an adjacent O vacancy (VO), from T to VO, and from O to VT, are estimated as 0.461, 0.668, 0.212, and 0.318 eV, respectively, which are comparable to experimental values. This means that diffusions of Ag ions between nonequivalent sites are preferable to those between equivalent sites, and that direct T-VT and O-VO diffusions are less likely to occur than indirect T-VO-T and O-VT-O diffusions. These diffusion behaviors between nonequivalent sites have also been supported by ab initio molecular dynamics simulations, in which the diffusion pathways are directly observed.

Structure change of liquid GaSb under pressure: an ab initio molecular-dynamics simulation.

We have performed ab initio molecular-dynamics simulation of liquid GaSb (l-GaSb) up to 20.0 GPa. The calculated structure factors are consistent with the recent experimental results, and the partial structure parameters show that the structure of l-GaSb under pressure contracts nonuniformly. In the whole calculated pressure region, the contraction of l-GaSb can be divided into three substages: 1.8-5.4, 5.4-10.0, and 10.0-20.0 GPa. It is further confirmed by analyzing the bond-angle distributions of Ga-Ga-Ga and Sb-Sb-Sb that the rearrangement of Sb atoms under pressure plays a crucial role in the structure change of l-GaSb.