Therefore, if the coverage of H or OH is 0.75 ML, their dangling bonds are fully occupied by paired electrons, and the remaining 25% of surface dangling bonds become empty, forming a closed-shell electronic structure. A closed-shell Fludarabine manufacturer electronic structure can be also formed by terminating the remaining 25% dangling bonds with H2O. As seen in Figure 2b, the differential adsorption energy of H2O is −1.93 eV, further stabilizing the OH-terminated GaN surface. An empty

Ga dangling bond attracts the lone pairs of H2O as observed at the water/GaN(10 0) interface [13]. Therefore, in the following calculations, we terminated 75% of surface Ga dangling bonds with OH and 25% with H2O. Dissociative adsorption of H2O We investigated two possible dissociative adsorption paths of H2O at stepped and kinked sites of Ga-terminated

LY3039478 chemical structure GaN surfaces as follows: (1) Side bond process: OH of a H2O molecule is bound to Ga at a step edge, and the remaining H of a water molecule is bound to N at a step edge (Figures 3c and 4c). Figure 3 Side bond process in a step-terrace structure. (a) Initial state, (b) transition state, and (c) final state. Figure 4 Side bond process in a kinked structure. (a) Initial state, (b) transition state, and (c) final state.   (2) Back bond process: OH is bound to Ga at a step edge, and the remaining H is bound to N at terrace (Figures 5d and 6d).   Figure 5 Back bond process in a step-terrace structure. (a) Initial state, (b) first transition state (c) second transition state, (d) final state. Figure 6 Back bond process in a kinked structure. (a) Initial state, (b) first transition state, (c) second transition state, and (d) final state. The potential energy profiles for the side bond process and the back bond process in a step-terrace structure are shown in Figures 7c and 8c as a function Idoxuridine of reaction coordinate S. Here, the reaction coordinate S is defined by the distance along the minimum

energy path obtained by the NEB method in the multidimensional configuration space. The side bond process has one transition state, and its reaction barrier is 1.35 eV. Figure 3 shows the atomic structures of the initial state, transition state, and final state of the side bond process. The back bond process has two transition states (Figure 5b,c), and its reaction barrier is 1.18 eV as seen in Figure 8c. Surface structures of the initial state, the first transition state, the second transition state, and the final state of the side bond process are shown in Figure 5. The bond lengths for the side bond and the back bond processes at the step-terrace structure are shown in Figures 7a and 8a, respectively. The positions of transition states are indicated by vertical lines. In the early stage of the side bond process (S≤0.2 nm), a water molecule approaches a surface Ga-N bond, and bond lengths of r(Ga-O) and r(N-H) are reduced, while no bonds are broken.