Quantum Computation with Effective Fragment Potential

描述（由申请人提供）：本第一阶段提案寻求对实施有效片段电位（EFP）方法的支持[J]。理论物理。化学。A， 105页，第293页（2001）]在Q-Chem电子结构程序。EFP方法使我能够处理具有局部相互作用的大型系统，方法是将它们分成量子力学（QM）处理的小“重要”部分（例如，反应中心）和环境，后者进一步细分为所谓的有效片段（EFs）。基于电磁场电子密度的多极展开描述了QM部分与电磁场之间的相互作用，并通过修正的单电子积分进行了描述。从概念上讲，EFP方法类似于流行的QM/MM（分子力学）方案，然而，它用从单个碎片的QM计算中得到的严格相互作用取代了经验的MM力场。一旦预先计算了EF的必要参数并将其存储在辅助数据库中，EF计算的成本与QM/MM计算的成本非常相似。在Q-Chem中实施EFP方法将使研究人员能够应用先进的QM方法（例如，运动方程和耦合簇方法）来研究生物分子、溶液和材料中的开壳和电子激发中心。

DESCRIPTION (provided by applicant): This Phase I proposal seeks support for implementing effective fragment potential (EFP) method [J. Phys. Chem. A, v.105 p.293 (2001)] in the Q-Chem electronic structure program. The EFP approach enables 1 to treat large systems with localized interactions by separating them into a small "important" part (e.g., reaction center) treated quantum mechanically (QM), and the environment, which is further subdivided into the so-called effective fragments (EFs). The interaction between the QM part and EFs is described based on multipolar expansions of EF's electronic density, and is included through the modified one-electron integrals. Conceptually, the EFP method is similar to the popular QM/MM (molecular mechanics) scheme, however, it replaces empirical MM force fields by rigorous interactions derived from QM calculations of individual fragments. Once the necessary parameters of EFs are pre-computed and stored in an auxiliary database, the cost of an EF calculation is very similar to that of a QM/MM one. The implementation of the EFP method in Q-Chem will enable the researchers to apply advanced QM methods (e.g., equation-of-motion and coupled-cluster methods) to study opens-shell and electronically excited centers in biological molecules, solutions, and materials.