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; Josefine H Andersen; Alice Balbi; Sonia Coriani; Tommaso Giovannini; Linda Goletto; Tor S Haugland; Anders Hutcheson; Ida-Marie Høyvik; Torsha Moitra; Alexander C Paul; Marco Scavino; Andreas S Skeidsvoll; Åsmund H Tveten; Henrik Koch

doi:10.1063/5.0004713

e^T 1.0: An open source electronic structure program with emphasis on coupled cluster and multilevel methods

J Chem Phys. 2020 May 14;152(18):184103. doi: 10.1063/5.0004713.

Authors

Sarai D Folkestad¹, Eirik F Kjønstad¹, Rolf H Myhre¹, Josefine H Andersen², Alice Balbi³, Sonia Coriani², Tommaso Giovannini¹, Linda Goletto¹, Tor S Haugland¹, Anders Hutcheson¹, Ida-Marie Høyvik¹, Torsha Moitra², Alexander C Paul¹, Marco Scavino³, Andreas S Skeidsvoll¹, Åsmund H Tveten¹, Henrik Koch¹

Affiliations

¹ Department of Chemistry, Norwegian University of Science and Technology, NO-7491 Trondheim, Norway.
² DTU Chemistry-Department of Chemistry, Technical University of Denmark, DK-2800 Kongens Lyngby, Denmark.
³ Scuola Normale Superiore, Piazza dei Cavalieri, 7, IT-56126 Pisa, PI, Italy.

PMID: 32414265
DOI: 10.1063/5.0004713

Abstract

The e^T program is an open source electronic structure package with emphasis on coupled cluster and multilevel methods. It includes efficient spin adapted implementations of ground and excited singlet states, as well as equation of motion oscillator strengths, for CCS, CC2, CCSD, and CC3. Furthermore, e^T provides unique capabilities such as multilevel Hartree-Fock and multilevel CC2, real-time propagation for CCS and CCSD, and efficient CC3 oscillator strengths. With a coupled cluster code based on an efficient Cholesky decomposition algorithm for the electronic repulsion integrals, e^T has similar advantages as codes using density fitting, but with strict error control. Here, we present the main features of the program and demonstrate its performance through example calculations. Because of its availability, performance, and unique capabilities, we expect e^T to become a valuable resource to the electronic structure community.