Local Quantum Theory for Large Molecular Systems

描述（由申请人提供）：Q-Chem是一个分子建模软件包，包含一些当今最先进的计算量子化学方法。它被用于模拟从生物化学到材料科学的各种学科中的原子和分子过程。这个第二阶段项目的目标是开发和实施一个通用的混合方案，以大大扩展分子系统的大小和复杂性，可以有效地用Q-Chem量子力学建模。目标系统包括含有数万个原子的分子，包括酶，含过渡金属的蛋白质和工业重要性的催化剂。新方法将为用户提供将不同计算方法应用于分子不同区域的选择。因此，基于高成本量子力学（QM）的方法可以应用于分子的关键区域（如酶的活性位点），其中精度是必不可少的，并且成本较低的方法可以应用于分子系统的其余部分。其结果是，用户将能够进行高度精确的基于量子力学的计算，而计算成本仅略有增加。该公式是完全通用的，保持了模拟中使用的每个理论的原始公式和性质，并且基于电子密度矩阵的分离，以更有效地处理量子力学和分子力学区域之间的界面。此外，所提出的计划是不限于QM/MM混合模拟，而是很容易扩展到QM/QM混合模拟。相应地，还将开发组合DFT/HF、DFT/SE、MP2/SE和MP2/HF方法。新的混合模型将使Q-Chem能够进入一个更大的市场，在这个市场上需要高水平的量子建模，但目前价格昂贵。

DESCRIPTION (provided by applicant): Q-Chem is a molecular modeling software package that contains some of the most advanced computational quantum chemistry methods available today. It is used to model atomic and molecular processes in a wide variety of disciplines, ranging from biological chemistry to materials science. The goal of this Phase II project is to develop and implement a general hybrid scheme to greatly extend the size and complexity of molecular systems that can be effectively modeled quantum mechanically with Q-Chem. Target systems include molecules containing tens of thousands of atoms, including enzymes, transition metal containing proteins, and catalysts of industrial importance. The new method will provide the user with the option of applying different computational methods to different regions of the molecule. Thus, a high-cost quantum mechanics (QM) based method can be applied to the critical area of the molecule (such as the active site of an enzyme) where accuracy is essential and a less-costly method can be applied to the rest of the molecular system. The result is that the user will be able to carry out highly accurate quantum mechanical based calculations with only minor increases in the computational cost. The formulism is completely general, maintains the original formulas and properties of each of the theories employed in the simulation, and is based on separation of the electron density matrix to more effectively treat the interface between the quantum mechanical and molecular mechanical regions. Furthermore, the proposed scheme is not limited to QM/MM hybrid simulations but rather is easily extended to QM/QM hybrid simulations. Accordingly, combined DFT/HF, DFT/SE, MP2/SE, and MP2/HF methods will also be developed. The new hybrid models will enable Q-Chem to reach a much larger market where high-level quantum modeling is desired but is currently prohibitively expensive.