Genetic-algorithm prediction of the magic-number structure of (C-60)(N) clusters with a first-principles interaction potential

A genetic algorithm has been employed, in combination with the first-princi ples Pacheco-Ramalho intermolecular potential, not only including its two-b ody part but also its dominant three-body term, to predict the magic number structure of neutral (C-60)(N) clusters up to N = 25. The calculated secon d finite difference of the total energy shows that the (C-60)(N) clusters W ith N = 7, 13, 18, and 22 are particularly stable. Present results indicate that the three-body effect is not significant for (C-60)(N) clusters with N less than or equal to 17, but above N = 17 we must consider the role play ed by the three-body dispersion term. It is found that N = 17 is a crossove r from icosahedral to decahedral, and for N greater than or equal to 23 (in clusion of the three-body term) icosahedral structures are always lower in energy than decahedra.