Full geometry optimization of all S₂ intermediates in OEC (oxygen-evolving complex) of PSII (photosystem II) were carried out by using UB3LYP-D3/Def2-TZVP with COSMO solvation effects. Our detail calculations yielded meta-stable structures of six (=3 × 2 (HS (high-spin), IS (intermediate-spin)) intermediates for W₁ = W₂ = H₂O and eight (=4 × 2 (HS, IS)) intermediates for W₁ = OH⁻ or W₂ = OH⁻, and were named to H₂O and OH models, respectively. In the next step, relative stability among these intermediate structures were investigated by hybrid-DFT and DLPNO-CC methods. UB3LYP methods show that right (R)-opened structures (open-cubane) are more stable than left (L)-opened structures (closed-cubane) by about 3.5 kcal/mol, though decreasing of DFT-weights suppresses such energy gaps. DLPNO-CCSD(T0) methods promote stabilization of (L)-structures and finally reproduce near degeneration or more stable (L)-structure. All pattern of spin configurations in four Mn(III) and Mn(IV) ions were assumed and BS (broken-symmetry) solutions were successfully obtained to find the most stable spin structures. This complete sets of all spin conformations enabled us evaluate sets of effective exchange integrals J as magnetic coupling parameters. The calculated J values for the spin Hamiltonian elucidated one g2 (S = 1/2) and two g4 (S = 5/2) molecular structures in the S₂ state in accord with the recent EXAFS results.

通过使用具有COSMO溶剂化作用的UB3LYP-D3 / Def2-TZVP，对PSII（光系统II）的OEC（放氧复合物）中的所有S ₂中间体进行了完整的几何优化。我们的详细计算得出W ₁ = W ₂ = H ₂ O和8（= 4×2（HS ）的六个（= 3×2（HS（高旋转），IS（中间旋转）））中间体的亚稳态结构，IS））的中间体用W ₁ = OH ^-或W ₂ = OH ^- ，和被命名为成H ₂O和OH模型。下一步，通过混合DFT和DLPNO-CC方法研究了这些中间结构之间的相对稳定性。UB3LYP方法显示，右（R）打开结构（开放式古巴）比左（L）打开结构（封闭式古巴）更稳定约3.5 kcal / mol，尽管DFT重量的减小抑制了这种能隙。DLPNO-CCSD（T0）方法可促进（L）结构的稳定，并最终重现近变性或更稳定的（L）结构。假定了四个Mn（III）和Mn（IV）离子中所有自旋构型的模式，并且成功获得了BS（破碎对称）溶液以找到最稳定的自旋结构。所有自旋构象的完整集合使我们能够评估有效交换积分J的集合作为磁耦合参数。自旋哈密顿量的计算J值阐明 了S ₂状态下的一个g 2（S  = 1/2）和两个g 4（S = 5/2）分子结构，这与最近的EXAFS结果一致。