Abstract
A full inclusion of the connected single (S), double (D) and triple (T) excitations into the equation-of-motion (EOM) coupled-cluster (CC) approach is discussed in the context of the calculations of excitation energies (EE), ionization potentials (IP) and electron affinity (EA). The EOM-CC formalism relies on the diagonalization of the CI-like matrix representing similarity transformed Hamiltonian H , defined as where T is a cluster operator. The H operator is non-Hermitian and – in the case of the EOM-CCSDT model – includes also three- and four-body elements which have to be treated in a special factorized manner to avoid very high scaling of the method and – at the same time – to keep the method fully rigorous. An analysis of the results indicates that the inclusion of triples for the EE reduces the average error twice and for the IP – three times. The performance of the EOM-CCSDT scheme for the electron affinity is more difficult to assess due to scarcity of the experimental data.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
