Quantum Computation with Effective Fragment Potential

描述（由申请人提供）：本I期提案寻求在Q-Chem电子结构计划中实施有效碎片电位（EFP）方法[J. Phys. Chem. A，v.105 p.293（2001）]的支持。EFP方法使1能够处理具有局部相互作用的大系统，将它们分成一个小的“重要”部分（例如，反应中心）处理的量子力学（QM），和环境，这是进一步细分为所谓的有效片段（EF）。QM部分和EF的电子密度的多极展开的基础上描述的相互作用，并包括通过修改的单电子积分。从概念上讲，EFP方法类似于流行的QM/MM（分子力学）计划，但是，它取代了经验MM力场的严格相互作用来自QM计算的单个片段。一旦EF的必要参数被预先计算并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.