<i>e</i> <i>T</i> 2.0: An efficient open-source molecular electronic structure program

S Sarai Dery Folkestad (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) E Eirik F. Kjønstad (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) A Alexander C. Paul (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) R Rolf H. Myhre (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) R Riccardo Alessandro (Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia 3 , 06123 Perugia,) S Sara Angelico (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) A Alice Balbi (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) A Alberto Barlini (Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,) A Andrea Bianchi (Scuola Normale Superiore 2 , Piazza dei Cavalieri 7, 56126 Pisa, PI,) C Chiara Cappelli (Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,) M Matteo Castagnola (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) S Sonia Coriani (Department of Chemistry) Y Yassir El Moutaoukal (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) T Tommaso Giovannini (Department of Physics, University of Rome Tor Vergata and INFN 6 , Via della Ricerca Scientifica 1, 00133 Rome,) L Linda Goletto (Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,) T Tor S. Haugland (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) D Daniel Hollas (School of Chemistry, University of Bristol 1 , Bristol BS8 1TS,) I Ida-Marie Høyvik (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) M Marcus T. Lexander (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) D Doroteja Lipovec (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) G Gioia Marrazzini (Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,) T Torsha Moitra (DTU Chemistry—Department of Chemistry, Technical University of Denmark 5 , DK-2800 Kongens Lyngby,) Y Ylva Os (Department of Chemistry, The Arctic University of Norway 9 , 9037 Tromsø,) R Regina Paul (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) J Jacob Pedersen (Department of Chemistry) M Matteo Rinaldi R Rosario R. Riso (Department of Chemistry, Norwegian University of Science and Technology, NTNU 1 , 7491 Trondheim,) S Sander Roet (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) E Enrico Ronca (Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia 3 , 06123 Perugia,) F Federico Rossi B Bendik S. Sannes (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) A Anna Kristina Schnack-Petersen (DTU Chemistry—Department of Chemistry, Technical University of Denmark 5 , DK-2800 Kongens Lyngby,) A Andreas S. Skeidsvoll (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) L Leo Stoll (Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,) G Guillaume Thiam (Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia 3 , 06123 Perugia,) J Jan Haakon M. Trabski (Department of Chemistry, Norwegian University of Science and Technology, NTNU 1 , 7491 Trondheim,) H Henrik Koch (Department of Chemistry, Norwegian University of Science and Technology, NTNU 1 , 7491 Trondheim,)

Abstract

The eT program is an open-source electronic structure program with an emphasis on performance and modularity. As its name suggests, the program features extensive coupled cluster capabilities, performing well compared to other electronic structure programs and, in some cases, outperforming commercial alternatives. However, eT is more than a coupled cluster program; other models based on wave function theory (such as full and reduced-space configuration interaction and a variety of self-consistent field models) and density functional theory are supported. The second major release of the program, eT 2.0, has specialized functionality for strong light–matter coupling conditions. In addition, it includes a wide range of optimizations and algorithmic improvements, as well as new capabilities for exploring potential energy surfaces and for modeling experiments in the ultraviolet and X-ray regimes. Molecular gradients are now available at the coupled cluster level, and high-accuracy spectroscopic simulations are available at reduced computational cost within the multilevel coupled cluster and multiscale frameworks. We present the modifications to the program since its first major release, eT 1.0, highlighting some notable new features and demonstrating the performance of the new version relative to the first release and to other established electronic structure programs.

Article Details

Volume / Issue Vol. 164, Issue 13
Published April 07, 2026
ISSN 0021-9606
Publisher American Institute of Physics

Journal Info

The Journal of Chemical Physics

American Institute of Physics

ISSN: 0021-9606 Physical Sciences

Authors (37)

S

Sarai Dery Folkestad

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

E

Eirik F. Kjønstad

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

A

Alexander C. Paul

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

R

Rolf H. Myhre

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

R

Riccardo Alessandro

Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia 3 , 06123 Perugia,

S

Sara Angelico

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

A

Alice Balbi

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

A

Alberto Barlini

Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,

A

Andrea Bianchi

Scuola Normale Superiore 2 , Piazza dei Cavalieri 7, 56126 Pisa, PI,

C

Chiara Cappelli

Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,

M

Matteo Castagnola

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

S

Sonia Coriani

Department of Chemistry

Y

Yassir El Moutaoukal

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

T

Tommaso Giovannini

Department of Physics, University of Rome Tor Vergata and INFN 6 , Via della Ricerca Scientifica 1, 00133 Rome,

L

Linda Goletto

Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,

T

Tor S. Haugland

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

D

Daniel Hollas

School of Chemistry, University of Bristol 1 , Bristol BS8 1TS,

I

Ida-Marie Høyvik

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

M

Marcus T. Lexander

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

D

Doroteja Lipovec

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

G

Gioia Marrazzini

Scuola Normale Superiore 4 , Piazza dei Cavalieri, 7, 56126 Pisa PI,

T

Torsha Moitra

DTU Chemistry—Department of Chemistry, Technical University of Denmark 5 , DK-2800 Kongens Lyngby,

Y

Ylva Os

Department of Chemistry, The Arctic University of Norway 9 , 9037 Tromsø,

R

Regina Paul

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

J

Jacob Pedersen

Department of Chemistry

M

Matteo Rinaldi

R

Rosario R. Riso

Department of Chemistry, Norwegian University of Science and Technology, NTNU 1 , 7491 Trondheim,

S

Sander Roet

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

E

Enrico Ronca

Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia 3 , 06123 Perugia,

F

Federico Rossi

B

Bendik S. Sannes

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

A

Anna Kristina Schnack-Petersen

DTU Chemistry—Department of Chemistry, Technical University of Denmark 5 , DK-2800 Kongens Lyngby,

A

Andreas S. Skeidsvoll

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

L

Leo Stoll

Department of Chemistry, Norwegian University of Science and Technology 1 , 7491 Trondheim,

G

Guillaume Thiam

Dipartimento di Chimica, Biologia e Biotecnologie, Università Degli Studi di Perugia 3 , 06123 Perugia,

J

Jan Haakon M. Trabski

Department of Chemistry, Norwegian University of Science and Technology, NTNU 1 , 7491 Trondheim,

H

Henrik Koch

Department of Chemistry, Norwegian University of Science and Technology, NTNU 1 , 7491 Trondheim,