本项目致力于将两种线性标度的电子相关方法与明确相关F12方法相结合，以期望获得复杂体系接近基组极限的精确结果。对于基于能量分块(GEBF)的方法，将把我们初步实现的GEBF-MP2-F12、GEBF-CCSD-F12和GEBF-CCSD(T)-F12方法从中等大小的分子簇等推广到一般性的复杂体系。对于基于局域分子轨道(LMO)的分子中的簇(CIM)方法，拟发展CIM-MP2-F12、CIM-CCSD-F12和CIM-CCSD(T)-F12方法，进一步推广到开壳层体系计算，并用于GEBF方法无法处理的体系如金属氧化物、局域自由基的计算。最后，使用发展的GEBF-X-F12和CIM-X-F12[其中X=MP2、CCSD和CCSD(T)]方法直接计算或作为其它电子结构方法如DFT的标定，结合GEBF-DFT、QM/MM等方法，我们将研究复杂体系(包括生物大分子、超分子、溶液体系等)中的相互作用。

This project aims to combine two linear scaling electron correlation methods with explicitly correlated F12 methods, which are expected to be able to obtain quite accurate results almost at the complete basis set (CBS) limit for complex systems. For the generalized energy-based fragmentation (GEBF) method, we will extend our recent GEBF-MP2-F12, GEBF-CCSD-F12, and GEBF-CCSD(T)-F12 methods from medium-sized molecular clusters to more general complex systems. For the locailized molecular orbital (LMO) based cluster-in-molecule (CIM) method, we will develope CIM-MP2-F12, CIM-CCSD-F12, and CIM-CCSD(T)-F12 methods and extend them to the calculations of open-shell systems. The CIM based F12 methods are expected to be used for the calculations of metal oxides and local radicals, which are not able to be performed with GEBF based F12 methods. Finally, the GEBF-X-F12 and CIM-X-F12 [X=MP2, CCSD, and CCSD(T)] methods will be used for direct calculations or as benchmark calculations to validate other electronic structure methods, such as density functional theory (DFT), for large systems. Then by combining these methods with GEBF-DFT and combined quantum mechanics and molecular mechanics (QM/MM) method, we will investigate the interaction energies in complex systems, including biological molecules, supramolecules, and condensed systems.