The magnitude of the geometric relaxation of surface Ga can be seen from the dihedral angle of Ga(step edge)-N(step edge)-Ga(second layer)-N(second layer) shown in Figures 7b, 8b, 13b, and 14b.

As seen in Figures 7b and 13b, the dihedral angle is changed by about only 10° during the reaction for the case of the side bond processes. On the other hand, for the case of the back bond process, the dihedral angle is changed by as large as 35° for the case of step-terrace selleck chemicals site and 50° for the case of kink site. Table 1 Barrier height and the energy of the final state relative to the initial state     Barrier height/eV Energy difference/eV   Step-terrace structure Side bond 1.35 1.06     Back bond 1.18 0.34   Kinked structure Side bond 0.95 0.58     Back bond 0.81 −0.04   It is found that the dissociative adsorption of water in the back bond process at the kinked structure is the most energetically favorable path we have investigated so far. Therefore, we think that etching reactions take place predominantly at kinked sites. Note that our kinked model represents an extreme case, and the activation barriers of dissociative adsorption of H2O should be somewhat larger than our calculated values but still smaller than those calculated for {Selleck Anti-infection Compound Library|Selleck Antiinfection Compound Library|Selleck Anti-infection Compound Library|Selleck Antiinfection Compound Library|Selleckchem Anti-infection Compound Library|Selleckchem Antiinfection Compound Library|Selleckchem Anti-infection Compound Library|Selleckchem Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|Anti-infection Compound Library|Antiinfection Compound Library|buy Anti-infection Compound Library|Anti-infection Compound Library ic50|Anti-infection Compound Library price|Anti-infection Compound Library cost|Anti-infection Compound Library solubility dmso|Anti-infection Compound Library purchase|Anti-infection Compound Library manufacturer|Anti-infection Compound Library research buy|Anti-infection Compound Library order|Anti-infection Compound Library mouse|Anti-infection Compound Library chemical structure|Anti-infection Compound Library mw|Anti-infection Compound Library molecular weight|Anti-infection Compound Library datasheet|Anti-infection Compound Library supplier|Anti-infection Compound Library in vitro|Anti-infection Compound Library cell line|Anti-infection Compound Library concentration|Anti-infection Compound Library nmr|Anti-infection Compound Library in vivo|Anti-infection Compound Library clinical trial|Anti-infection Compound Library cell assay|Anti-infection Compound Library screening|Anti-infection Compound Library high throughput|buy Antiinfection Compound Library|Antiinfection Compound Library ic50|Antiinfection Compound Library price|Antiinfection Compound Library cost|Antiinfection Compound Library solubility dmso|Antiinfection Compound Library purchase|Antiinfection Compound Library manufacturer|Antiinfection Compound Library research buy|Antiinfection Compound Library order|Antiinfection Compound Library chemical structure|Antiinfection Compound Library datasheet|Antiinfection Compound Library supplier|Antiinfection Compound Library in vitro|Antiinfection Compound Library cell line|Antiinfection Compound Library concentration|Antiinfection Compound Library clinical trial|Antiinfection Compound Library cell assay|Antiinfection Compound Library screening|Antiinfection Compound Library high throughput|Anti-infection Compound high throughput screening| stepped sites. Before closing our discussion, we mention about roles of additional water molecules terminating

empty Ga dangling bonds. As discussed above, 75% of surface Ga dangling bonds are terminated by OH and 25% are by H2O. Selleck NVP-BSK805 These additional H2O molecules initiate proton transfer on the GaN surfaces and promote chemical reactions at surfaces as discussed by TCL Wang and co-workers [13]. Actually, additional water molecules play an active role in two step

processes of H2O dissociation, in which H2O molecule is dissociated, OH is bound to surface Ga, and H is bound to neighboring H2O (MO et al., unpublished results). Following this process, proton transfer takes place to terminate a dangling bond at subsurface N. However, in the direct H2O dissociation we have investigated in the present study, it seems that the additional water molecules are spectator of the reaction, and they play a rather minor role. Conclusions In summary, we have investigated the initial stage of hydrolysis process of Ga-terminated GaN surfaces by using first-principles theoretical calculations. The activation barrier of H2O dissociation at kinked sites of the Ga-terminated GaN(0001) surface is about 0.8 eV, which is significantly lower than that at stepped sites of about 1.2 eV, suggesting that etching reactions take place predominantly at kinked sites of GaN surfaces; and this is consistent with the experimental observation where a step-terrace structure is observed after the etching process of Ga-terminated GaN(0001) surfaces with CARE method.