Development of local Coupled Cluster Linear Response method for the calculation of excited state properties of extended molecular systems

点击翻译按钮获取中文摘要

During the last decade novel ab initio methods targeting extended molecular systems have been developed. These methods are characterised by comparatively low scalings of the computational cost with molecular size. In the context of the treatment of electron correlation this was achieved by exploiting the short-range nature of dynamic correlation effects by virtue of Local Correlation methods. Local Correlation methods, especially in combination with the Density Fitting approximation for the evaluation of electron repulsion integrals, are nowadays a valuable tool to treat systems at highly correlated levels (e.g. Coupled Cluster (CC) theory), which otherwise would only be accessible by less accurate methods, such as Density Functional Theory. However, presently, these methods are restricted to ’closed shell’ configurations in the electronic Ground State (GS). The aim of the present project is the development of local correlation methods for properties of electronically excited states, based on time-dependent CC (response) theory. As the underlying CC model we choose CC2 and local approximations are introduced only for the costly doubles substitutions.