7 papers
Oscillator strengths in the framework of equation of motion multilevel CC3
Alexander C. Paul, Sarai D. Folkestad, Rolf H. Myhre +1
We present an efficient implementation of the equation of motion oscillator strengths for the closed-shell multilevel coupled cluster singles and doubles with perturbative triples…
Combining Multilevel Hartree Fock and Multilevel Coupled Cluster with Molecular Mechanics: a Study of Electronic Excitations in Solutions
Linda Goletto, Tommaso Giovannini, Sarai D. Folkestad +1
We investigate the coupling of different quantum-embedding approaches with a third molecular-mechanics layer, which can be either polarizable or non-polarizable. In particular, suc…
Equation-of-motion MLCCSD and CCSD-in-HF oscillator strengths and their application to core excitations
Sarai D. Folkestad, Henrik Koch
We present an implementation of equation-of-motion oscillator strengths for the multilevel CCSD (MLCCSD) model where CCS is used as the lower level method (CCS/CCSD). In this model…
Multilevel CC2 and CCSD in reduced orbital spaces: electronic excitations in large molecular systems
Sarai D. Folkestad, Eirik F. Kjønstad, Linda Goletto +1
We present efficient implementations of the multilevel CC2 (MLCC2) and multilevel CCSD (MLCCSD) models. As the system size increases, MLCC2 and MLCCSD exhibit the scaling of the lo…
Accelerated multimodel Newton-type algorithms for faster convergence of ground and excited state coupled cluster equations
Eirik F. Kjønstad, Sarai D. Folkestad, Henrik Koch
We introduce a multimodel approach to solve coupled cluster equations, employing a quasi Newton algorithm for the ground state and an Olsen algorithm for the excited states. In the…
eT 1.0: an open source electronic structure program with emphasis on coupled cluster and multilevel methods
Sarai D. Folkestad, Eirik F. Kjønstad, Rolf H. Myhre +14
The eT program is an open source electronic structure package with emphasis on coupled cluster and multilevel methods. It includes efficient spin adapted implementations of ground…