60 citations · 60 across the 2 of their papers we have counts for
8 papers
A biorthonormal formalism for nonadiabatic coupled cluster dynamics
Eirik F. Kjønstad, Henrik Koch
In coupled cluster methods, the electronic states are biorthonormal in the sense that the left states are orthonormal to the right states. Here we present an extension of this form…
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…
Coupled Cluster Theory for Molecular Polaritons: Changing Ground and Excited States
Tor S. Haugland, Enrico Ronca, Eirik F. Kjønstad +2
We present an ab initio correlated approach to study molecules that interact strongly with quantum fields in an optical cavity. Quantum electrodynamics coupled cluster theory provi…
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…
An efficient algorithm for Cholesky decomposition of electron repulsion integrals
Sarai D. Folkestad, Eirik F. Kjønstad, Henrik Koch
We present an algorithm where only the Cholesky basis is determined in the decomposition procedure. This allows for improved screening and a partitioned matrix decomposition scheme…