dc.contributor.advisor | Høyvik, Ida-Marie | |
dc.contributor.author | Folkestad, Sarai Dery | |
dc.date.accessioned | 2019-09-11T10:36:01Z | |
dc.date.created | 2016-06-10 | |
dc.date.issued | 2016 | |
dc.identifier | ntnudaim:14497 | |
dc.identifier.uri | http://hdl.handle.net/11250/2615627 | |
dc.description.abstract | The description of high-spin open-shell systems with coupled cluster (CC) theory presents problems not encountered in the closed-shell case. Spin-contamination and additional computational cost compared to closed-shell calculations are the major challenges, and these have so far only been remedied at the cost of a more complicated CC theory and implementation.
In this work a new CC singles and doubles (CCSD) scheme for doublet systems was developed, where an alternative closed-shell mixed orbital reference was used instead of an open-shell Hartree-Fock reference. The alternative reference makes possible the use of the closed-shell CCSD formalism. The objective is easy implementation and costs approaching that of the comparable closed-shell calculation. The CCSD wave function is spin-contaminated but satisfies ⟨R|S^2|CCSD⟩ = s(s + 1), where |R⟩ is the mixed orbital reference and S^2 is the operator for the total spin of the open-shell system.
The new mixed orbital CCSD (MXO-CCSD) method was implemented by making only a few adaptations to the closed-shell CCSD code of the DALTON software. Energy calculations were performed for the two smallest atomic doublets with electron correlation, Lithium and Boron, and the peroxy radicals O2^−, HO2 and CH3O2. MXO-CCSD results for these doublet systems are comparable to other CCSD methods for open-shell systems. For the atoms more than 89% of the correlation energy is recovered.
The initial steps towards the development of MXO-CCSD for triplet systems were also taken. | en |
dc.language | eng | |
dc.publisher | NTNU | |
dc.subject | Industriell kjemi og bioteknologi, Kjemi | en |
dc.title | Coupled Cluster for High-Spin Open-Shell Systems - A Mixed Orbital Approach | en |
dc.type | Master thesis | en |
dc.source.pagenumber | 65 | |
dc.contributor.department | Norges teknisk-naturvitenskapelige universitet, Fakultet for naturvitenskap,Institutt for kjemi | nb_NO |
dc.date.embargoenddate | 10000-01-01 | |