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The generalized energy-based fragmentation(GEBF)approach[1] has been implemented for the explicitly correlated second-order M(o)ller-Plesset perturbation theory F12(MP2-F12)method,coupled-cluster with the noniterative triples corrections F12a [CCSD(T)-F12a] method,and their multilayer extensions(GEBF-X/Y)for large systems.[2-3] Here X could be any electron correlation method and Y could be GEBF-MP2,Hartree-Fock(HF),and etc.The GEBF-X/HF method is illustrated to be more accurate than the origin GEBF-X method.With the GEBF-MP2-F12/HF and GEBF-CCSD(T)-F12a/HF methods,we can achieve the MP2 and CCSD(T)complete basis set(CBS)limits,respectively.Our test calculations for ten water 20-mers show that for the relative energies of large water clusters,both the basis set and high-level electron correlation effects should be taken into account.The density functional theory(DFT)results are shown to be difficult to predict the relative energies between the isomers of water 20-mers.In addition,we have investigated the long-range interaction in large methanol-(H2O)n clusters up to 747 atoms(10209 basis functions with the aug-cc-pVDZ basis set)at the GEBF-MP2-F12/GEBF-MP2 level or 3351 atoms by further including density-functional tight-binding method.Thus,the GEBF-MP2-F12 and GEBF-CCSD(T)-F12a methods are expected to be practical tools for large system and can provide as benchmarks for DFT and other electron correlation methods.