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In this paper, we report on the implementation of CC2 and CC3 in the context of molecules in finite magnetic fields. The methods are applied to the investigation of atoms and molecules through spectroscopic predictions and geometry…

Chemical Physics · Physics 2024-03-08 Marios-Petros Kitsaras , Laura Grazioli , Stella Stopkowicz

Using resonantly excited photoluminescence along with photoluminescence excitation spectroscopies, we study the carrier excitation processes in CdTe/ZnTe and CdSe/ZnSe self-assembled quantum dots. Photoluminescence excitation spectra of…

Use of density-functional theory in a $\Delta$self-consistent field framework result in both the ground- and two lowest electronicly excited states of the NaCl and LiCl. The accuracy of this method is confirmed using a multi-configuration…

Chemical Physics · Physics 2007-05-23 A. Hellman , M. Slabanja

We study the ground and low-lying excited states of O-15, O-17, N-15, and F-17 using modern two-body nucleon-nucleon interactions and the suitably designed variants of the ab initio equation-of-motion coupled-cluster theory aimed at an…

Nuclear Theory · Physics 2009-11-11 J. R. Gour , P. Piecuch , M. Hjorth-Jensen , M. Wloch , D. J. Dean

To expand the existing QUEST database of accurate vertical transition energies [\href{https://doi.org/10.1002/wcms.1517}{V\'eril et al.~\textit{WIREs Comput.~Mol.~Sci.} \textbf{2021}, \textit{11}, e1517}], we have modeled more than 100…

Chemical Physics · Physics 2024-01-26 Pierre-François Loos , Denis Jacquemin

We revisit the connection between equation-of-motion coupled cluster (EOM-CC) and random phase approximation (RPA) explored recently by Berkelbach [J. Chem. Phys. 149, 041103 (2018)] and unify various methodological aspects of these diverse…

Chemical Physics · Physics 2020-12-17 Varun Rishi , Ajith Perera , Rodney J. Bartlett

We consider a fermionic system for which there exist a single-reference configuration-interaction (CI) expansion of the ground state wave function that converges, albeit not necessarily rapidly, with respect to excitation number. We show…

Strongly Correlated Electrons · Physics 2020-01-13 Dominic Bergeron

By correlating only the 1-particle states occupied in the reference determinant the conventional design for the single-reference R12/F12 explicitly-correlated methods biases them towards the ground state description thereby making treatment…

Chemical Physics · Physics 2025-10-13 Conner Masteran , Bimal Gaudel , Edward F. Valeev

We study the excitation spectroscopy of few-electron, parallel coupled double quantum dots (QDs). By applying a finite source drain voltage to a double QD (DQD), the first excited states observed in nonequilibrium charging diagrams can be…

Mesoscale and Nanoscale Physics · Physics 2013-07-01 T. Hatano , Y. Tokura , S. Amaha , T. Kubo , S. Teraoka , S. Tarucha

Despite their high accuracy, standard coupled cluster models cannot be used for nonadiabatic molecular dynamics simulations because they yield unphysical complex excitation energies at conical intersections between same-symmetry excited…

Chemical Physics · Physics 2025-04-16 Leo Stoll , Sara Angelico , Eirik F. Kjønstad , Henrik Koch

The development of a quadratic unitary coupled-cluster singles and doubles (qUCCSD) based self-consistent polarization propagator method is reported. We present a simple strategy for truncating the commutator expansion of the UCC…

Chemical Physics · Physics 2024-06-19 Junzi Liu , Lan Cheng

We reveal limitations of several standard coupled-cluster (CC) methods with perturbation-theorybased noniterative or approximate iterative treatments of triple excitations when applied to thedetermination of highly accurate potential energy…

Chemical Physics · Physics 2021-10-04 Jan Schnabel , Lan Cheng , Andreas Köhn

Employing high accuracy fixed node diffusion Monte Carlo (DMC) method we calculated the lowest triplet collective excitation (spin gap), as well as an upper bound for the singlet excitations (charge gap) in a series of charge neutral planar…

Strongly Correlated Electrons · Physics 2011-10-19 K. Haghighi Mood , S. A. Jafari , E. Adibi , G. Baskaran , M. R. Abolhassani

Ab initio methods based on the second-order and higher connected moments, or cumulants, of a reference function have seen limited use in the determination of correlation energies of chemical systems throughout the years. Moment-based…

Chemical Physics · Physics 2023-08-25 Brad Ganoe , Martin Head-Gordon

Quantum chemistry simulations offer a cost-effective way for computational design of BODIPY photosensitizers with potential use in photodynamic therapy (PDT). However, accurate predictions of photophysical properties, such as excitation…

Coupled-cluster theory with single and double excitations (CCSD) is a promising ab initio method for the electronic structure of three-dimensional metals, for which second-order perturbation theory (MP2) diverges in the thermodynamic limit.…

Materials Science · Physics 2021-06-16 James M. Callahan , Malte F. Lange , Timothy C. Berkelbach

The accurate calculation of excited state properties of interacting electrons in the condensed phase is an immense challenge in computational physics. Here, we use state-of-the-art equation-of-motion coupled-cluster theory with single and…

Chemical Physics · Physics 2019-07-10 Alan M. Lewis , Timothy C. Berkelbach

We have studied electron correlations in the doped two-dimensional (2D) Hubbard model by using the coupled-cluster method (CCM) to investigate whether or not the method can be applied to correct the independent particle approximations…

Strongly Correlated Electrons · Physics 2009-10-31 Yoshihiro Asai , Hideki Katagiri

The issue of orbital relaxation in computational core-hole spectroscopy, specifically x-ray absorption, has been a major problem for methods such as equation-of-motion coupled cluster with singles and doubles (EOM-CCSD). The…

Chemical Physics · Physics 2025-03-26 Megan Simons , Devin A. Matthews

Density functional calculations of Rydberg excited states up to high energy are carried out for several molecules using an approach where the orbitals are variationally optimized by converging on saddle points on the electronic energy…