The local mean field approximation is applied to an inhomogeneous 3D spin crossover (SCO) nanoparticle configuration with a special focus on its systemic effect on molecules in the bulk, at the corner, at the edge and at surface. The matrix effect at the surface is introduced through a specific interaction term, L. The partition function for each region allows the determination of the total free-energy F from which the stability of each configuration is analyzed through thermodynamic considerations.