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.