A dynamic-correlation doubles correction to CASSCF linear response excitation energies

该项目的目标是引入对CASSCF线性响应(MCRPA)激发能量的双重(D)校正。这种激发-能量校正以微扰的方式引入了动力学关联，将显著提高MCRPA的精度。结合MCRPA(D)方法，可以在局域激发和电荷转移激发下精确计算中型开壳过渡金属络合物的核激发能和价激发能。用现有的方法，这些计算目前还不可能以令人满意的方式进行。此外，我将致力于对可能发生在开壳轨道-近简并TMC中的自旋-翻转跃迁的(D)校正的公式和实现。为了能够进行更大的活动空间(D)计算，将寻求对所谓的库普曼矩阵进行有效的重新表述。

The goal of the project is the introduction of a doubles (D) correction to CASSCF linear response (MCRPA) excitation energies. This excitation-energy correction introduces dynamical correlation in a perturbative manner and will significantly improve the accuracy of MCRPA. With the combined MCRPA(D) method, the calculation of accurate core and valence excitation energies of medium-sized open-shell transition metal complexes will be possible for both local and charge-transfer excitations. With existing methods, these calculations are currently not yet possible in a satisfactory fashion. Moreover, I will work on a formulation and implementation of a (D) correction for spin-flip transitions that occur likely in open-shell orbital-near degenerate TMC. To enable larger-active space (D) calculations, an efficient reformulation of so-called Koopmans matrices will be pursued.