Gaussian Approximation Potential for Gallium Nitride

So far our tests of the Gaussian Approximation Potentials were limited to singlespecies systems, but the framework can be extended to multispecies systems. Here we report our first attempt to model such a system, the cubic phase of gallium nitride. Gallium nitride (GaN) is a two-component semiconductor with a wurtzite or zinc-blende structure. There is a charge transfer between the two species. 

We checked the correlation of the predicted forces of the resulting GAP potential with the ab initio forces, and the results are shown in Fig. 6.20. We used 64-atom configurations where the atoms were randomly displaced by similar amounts to the training conhgurations. The phonon spectmm calculated by GAP is shown in Fig. 6.21 and the elastic moduli are listed in Table 6.6. 

Even this simple GAP model for gallium nitride shows remarkable accuracy in these tests, which we take as evidence that we can adapt GAP to multispecies 

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