Efficient algorithms for coupled cluster with approximate triples for larger molecular systems
Doctoral thesis
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https://hdl.handle.net/11250/2979955Utgivelsesdato
2021Metadata
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- Institutt for kjemi [1358]
Sammendrag
Spectroscopic techniques are widely used to study matter in a non-invasive manner. With increasing complexity of the experiments conducted, theoretical simulations become more important to gain additional insight into the electronic structure of the molecules investigated.
Due to its accuracy, coupled cluster theory is often the method of choice for these simulations. However, the high computational cost of these methods severely limits the size of the systems that can be studied.
In this thesis an efficient algorithm for the CC3 method was implemented. Using this algorithm, the transient absorption spectra of the nucleobases could be investigated providing accurate benchmark results for these molecules. To be able to calculate spectroscopic properties of larger molecular systems, the multilevel CC3 method was extended and optimized. In multilevel methods, only a small, active part of a molecule is treated with an accurate but expensive method like CC3, while a less expensive method is applied to the remaining part of the system. By choosing an appropriate active part, the targeted property can be described at significantly reduced cost, while retaining the accuracy of the high-level method.