Accessing the applicability of the MBE approach for constructing potential energy surfaces of nitrogen clusters.

The many-body expansion approach (MBE) is employed to build potential energy surfaces (PESs) for nitrogen clusters, which serve as a possible candidate of high energy density materials. The ground-state global PES of N 4 developed by Truhlar's group is utilized to construct the two-body, three-body, and four-body interaction potentials. The energy of nitrogen clusters is thus obtained by summing the many-body interaction energies up to four-body term. This work found that such a many-body expansion could give reasonable energy predictions for loose chain nitrogen molecules while produce bad predictions for compact structures. The failure is caused by the neglect of high-order (n ≥ 5) n -body interactions that are significant in the bonding area. The difficulties in applying the MBE method to construct the potential energy surface of nitrogen clusters are analyzed. [ABSTRACT FROM AUTHOR]