The PM7 method is to be used. This keyword is redundant, because the default method in MOPAC2016 is PM7. See also PM7 Accuracy
PM7 uses a "D2" type correction. Elements supported are: H, He, B, C, N, O, F, Ne, P, S, Cl, Ar, Br, and Kr. For the other elements, a core-core Gaussian attractive terms is used to mimic dispersion. This means that some form of dispersion is present for all elements. The core-core Gaussian terms are optimized to reproduce reference geometries and heats of formation.