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Fourth-order many-body corrections to matrix elements for atoms with one valence electron are derived. The obtained diagrams are classified using coupled-cluster-inspired separation into contributions from n-particle excitations from the…

Atomic Physics · Physics 2009-11-07 Andrei Derevianko , Erik D. Emmons

Unitary Coupled Cluster (UCC) theory is a promising variational method for electronic structure calculations, especially for strongly correlated systems and quantum computers. However, its practical application is limited by the steep…

Chemical Physics · Physics 2026-02-05 Prateek Vaish , Brenda Rubenstein

The previously proposed ansatz for density cumulant theory that combines orbital-optimization and a parameterization of the 2-electron reduced density matrix cumulant in terms of unitary coupled cluster amplitudes (OUDCT) is carefully…

Chemical Physics · Physics 2020-12-23 Jonathon P. Misiewicz , Justin M. Turney , Henry F. Schaefer , Alexander Yu. Sokolov

Here we demonstrate workably accurate estimation of optical excitation threshold for large systems comprising of hundreds of atoms through an anti-causally corrected(ACC) real-time dynamics(RTD) approach implemented in a minimal…

Materials Science · Physics 2023-06-13 Joydev De , Manoar Hossain , Joydeep Bhattacharjee

The tailored coupled cluster (TCC) approach is a promising ansatz that preserves the simplicity of single-reference coupled cluster theory, while incorporating a multi-reference wave function through amplitudes obtained from a preceding…

Chemical Physics · Physics 2021-01-07 Maximilian Mörchen , Leon Freitag , Markus Reiher

We describe the time-dependent restricted-active-space self-consistent-field (TD-RASSCF) method for a system of interacting bosons. We provide the theory of the method and discuss its numerical implementation. The method provides a general…

Quantum Physics · Physics 2017-04-28 Camille Lévêque , Lars Bojer Madsen

We present an implementation of the multiconfiguration time-dependent Hartree-Fock method based on the adaptive finite element method for molecules under intense laser pulses. For efficient simulations, orbital functions are propagated by a…

Quantum Physics · Physics 2023-01-09 Yuki Orimo , Takeshi Sato , Kenichi L. Ishikawa

Coupled cluster methods based exclusively on double excitations are comparatively "cheap" and interesting model chemistries, as they are typically able to capture the bulk of the dynamical electron correlation effects. The trade-off in such…

Quantum Physics · Physics 2024-06-14 Zachary W. Windom , Daniel Claudino , Rodney J. Bartlett

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

We introduce a non-iterative energy correction, added on top of the rank-reduced coupled-cluster method with single, double, and triple substitutions, that accounts for excitations excluded from the parent triple excitation subspace. The…

Chemical Physics · Physics 2022-01-06 Michał Lesiuk

We present a new formulation of the time-dependent self-interaction correction (TDSIC). It is derived variationally obeying explicitly the constraints on orthonormality of the occupied single-particle orbitals. The thus emerging rather…

Quantum Physics · Physics 2009-03-02 J. Messud , P. M. Dinh , P. -G. Reinhard , E. Suraud

The (T) and [T] perturbative corrections are derived for multicomponent coupled-cluster theory with single and double excitations (CCSD). Benchmarking shows that multicomponent CCSD methods that include the perturbative corrections are more…

Chemical Physics · Physics 2022-07-01 Dylan Fowler , Kurt R. Brorsen

This chapter provides a basic introduction to excited-state extensions of density functional theory (DFT), including time-dependent (TD-)DFT in both its linear-response and its explicitly time-dependent formulations. As applied to the…

Chemical Physics · Physics 2023-05-02 John M. Herbert

The structure of approximate two electron wavefunction is deeply investigated, both theoretically and numerically, in the strong-field driven ionization dynamics. Theoretical analyses clarify that for two electron singlet systems, the…

Atomic Physics · Physics 2014-11-13 Takeshi Sato , Kenichi L Ishikawa

Charged excitations of the oligoacene family of molecules, relevant for astrophysics and technological applications, are widely studied and therefore provide an excellent system for benchmarking theoretical methods. In this work, we…

Chemical Physics · Physics 2016-05-18 Tonatiuh Rangel , Samia M. Hamed , Fabien Bruneval , Jeffrey B. Neaton

A new method that accurately describes strongly correlated states and captures dynamical correlation is presented. It is derived as a modification of coupled-cluster theory with single and double excitations (CCSD) through consideration of…

Chemical Physics · Physics 2013-07-15 Daniel Kats , Frederick R. Manby

We adopted the time-dependent density functional theory (TDDFT) within the linear augmented Slater-type orbitals (LASTO) basis and the cluster averaging method to compute the {\color{red}excitation} spectra of III-V ternary alloys with…

Computational Physics · Physics 2017-09-14 Zhenhua Ning , Ching-Tarng Liang , Yia-Chung Chang

A novel reduced-scaling, general-order coupled-cluster approach is formulated by exploiting hierarchical representations of many-body tensors, combined with the recently suggested formalism of scale-adaptive tensor algebra. Inspired by the…

Chemical Physics · Physics 2018-03-14 Dmitry I. Lyakh

Accurately resolving many-body satellite features in molecular core-level spectra requires theoretical approaches that capture electron correlation both efficiently and systematically. The recently developed time-dependent double…

Quantum Physics · Physics 2026-05-12 Vibin Abraham , Priyabrata Senapati , Himadri Pathak , Bo Peng

The phenomenon of orbital relaxation upon excitation of core electrons is a major problem in the linear-response treatment of core-hole spectroscopies. Rather than addressing relaxation through direct dynamical correlation of the excited…

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