Calculation of zero-field splitting parameters by density functional theory and ab-initio methods

激发态三重态的光谱分析在众多研究领域中占有重要的地位。特别是，研究这种状态对于理解许多重要的生物系统的结构和反应性是必不可少的。理论处理可以从多个方面促进这方面的研究：(1)计算电子激发态的结构和能面。(2)对激发态电子结构的定性分析。(3)计算激发三重态的光谱性质，用于(A)检验计算的波函数(更确切地说是电子和自旋密度)的质量，以及(B)解释复杂的实验光谱。这项建议旨在基于Hartree-Fock(HF)和密度泛函理论(DFT)以及关联从头计算方法计算激发三重态的磁性。零场分裂张量是EPR实验中可获得的重要参数之一，它描述了零场作用下S=1态的MS=0，±1分量的分裂。用于计算大系统ZFS参数的可靠的量子化学方法和程序仍然很少。将开发和测试用于计算这些性质的通用程序。要完成的任务包括：1.开发和实施恒等式解析(或密度拟合)技术，以加快大系统自旋-自旋相互作用的计算；2.在完整的活动空间自洽场从头计算水平上，同时考虑自旋-自旋和自旋-轨道相互作用的全变分处理；3.新实施方法的验证；4.在生物相关系统中的应用。

The spectroscopic analysis of the excited triplet states plays an important role in diverse research fields. In particular, studying such states is essential for understanding the structure and reactivity of many important biological systems. Theoretical treatments can contribute to this research in various directions: (1) Calculation of the structure and energy surfaces of electronically excited states. (2) Qualitative analysis of the electronic structure of excited states. (3) Calculation of spectroscopic properties of excited triplet states, for (a) testing the quality of the calculated wave function or rather the electron and spin densities, and (b) the interpretation of the complex experimental spectra.This proposal is aimed at the calculation of the magnetic properties of the excited triplet states on the basis of Hartree-Fock (HF) and density functional theory (DFT) as well as correlated ab initio approaches. One of the important accessible parameters from EPR experiments is the zerofield splitting tensor, which describes the splitting of the MS= 0, ±1 components of the S = 1 state in zero applied magnetic field. Reliable quantum chemical methods and programs for the calculation of ZFS parameters for large systems are still scarce. A generally applicable program for the calculation of such properties will be developed and tested. Tasks to be completed include:1. Development and implementation of a resolution of identity (or density fitting) technique to speed up calculations of the spin-spin interaction for large systems;2. Implementation of a fully variational treatment that simultaneously accounts for the spin-spin and spin-orbit interactions on the complete active space self-consistent field ab initio level;3. Validation of the newly implemented methods;4. Application to biologically relevant systems.