Generalized energy-based fragmentation DLPNO-CCSD(T) approach at complete basis set limit and its application to benzene clusters

Accurate description of noncovalent interactions in large systems is challenging due to the requirement of high-level electron correlation methods. The generalized energy-based fragmentation (GEBF) approach, in conjunction with the domain-based local pair natural orbital (DLPNO) method, has been applied to assess the average binding energies (ABEs) of large benzene clusters, specifically (C6H6)13, at the coupled cluster singles and doubles with perturbative triples correction [CCSD(T)] level and the complete basis set (CBS) limit. Utilizing GEBF-DLPNO-CCSD(T)/CBS ABEs as benchmarks, various DFT functionals were evaluated. It was found that several functionals with empirical dispersion correction, including M06-2X-D3, B3LYP-D3(BJ), and PBE-D3(BJ), provide accurate descriptions of the ABEs for (C6H6)13 clusters. Additionally, the M06-2X-D3 functional was used to calculate the ABEs and relative stabilities of (C6H6)n clusters for n=11, 12, 13, 14, and 15 revealing that the (C6H6)13 cluster exhibits the highest relative stability. These findings align with experimental evidence suggesting that n=13 is one of the magic numbers for benzene clusters (C6H6)n, with n ≤ 30.