A DFT based method for calculating the surface energies of asymmetric MoP facets    

MoP is a promising catalyst in heterogeneous catalysis. Understanding its surface stability and morphology is the first and essential step in exploring its catalytic properties. However, traditional surface energy calculation method does not work for the asymmetric termination of MoP. In this work, we reported a useful DFT based method to get the surface energies of asymmetric MoP facets. Under ideal condition, the (101) surface with mixed Mo/P termination is most stable, followed by the (100) surface, while the (001) surface is least stable. Wulff construction reveals the exposure of six surfaces on the MoP nanoparticle, where the (101) has the largest contribution. Atomistic thermodynamics results reveal the changes in surface stability orders with experimental conditions, and the (001)-P termination becomes more and more stable with increasing P chemical potential, which indicates its exposure is possible at defined conditions. Our results agree well with the previous experimental XRD and TEM data. We believe the reported method for surface energy calculation could be extended to other similar systems with asymmetric surface terminations.