The results are 0.015 and -0.027 e, respectively, which are fairly low values indicating that intermolecular charge transfer is completely negligible. Furthermore, the total Mayer bond order for all atomic pairs between C18 and C60 fullerene was calculated to estimate effective number of shared electron pairs between the two molecules. The very small value of 0.041 reflects that the C60C18 interaction is undeniable non-covalent.