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A dynamical formulation of coupled cluster theory is derived using a variational principle. By allowing time-dependent single-particle functions, a high degree of adaptivity is introduced, allowing complex systems to be simulated with high…

Quantum Physics · Physics 2014-11-25 Simen Kvaal

We present a spin-adapted time-dependent coupled cluster singles and doubles model for the molecular response to a sequence of ultrashort laser pulses. The implementation is used to calculate the electronic response to a valence-exciting…

Chemical Physics · Physics 2020-08-28 Andreas S. Skeidsvoll , Alice Balbi , Henrik Koch

In this work we present a coupled-cluster theory for the propagation of multireference electronic systems initiating at general quantum mechanical states. Our formalism is based on the infinitesimal analysis of modified cluster operators,…

Chemical Physics · Physics 2025-05-09 Martín A. Mosquera

We present the development and implementation of the relativistic coupled cluster linear response theory (CC-LR) which allows the determination of molecular properties arising from time-dependent or time-independent electric, magnetic, or…

We study time-dependent coupled-cluster theory in the framework of nuclear physics. Based on Kvaal's bi-variational formulation of this method [S. Kvaal, arXiv:1201.5548], we explicitly demonstrate that observables that commute with the…

Nuclear Theory · Physics 2012-07-04 D. A. Pigg , G. Hagen , H. Nam , T. Papenbrock

The formulation of the time-dependent Schrodinger equation in terms of coupled-cluster theory is outlined, with emphasis on the bivariational framework and its classical Hamiltonian structure. An indefinite inner product is introduced,…

Chemical Physics · Physics 2019-04-16 Thomas Bondo Pedersen , Simen Kvaal

We introduce a simple definition of the weight of any given Slater determinant in the coupled-cluster state, namely as the expectation value of the projection operator onto that determinant. The definition can be applied to any…

Chemical Physics · Physics 2025-03-05 Håkon Emil Kristiansen , Håkon Kvernmoen , Simen Kvaal , Thomas Bondo Pedersen

Time-dependent response theories are foundational to the development of algorithms that determine quantum properties of electronic excited states of molecules and periodic systems. They are employed in wave-function, density-functional, and…

Chemical Physics · Physics 2022-11-23 Martín A. Mosquera

We review time-dependent multiconfiguration self-consistent-field (TD-MCSCF) method and time-dependent optimized coupled-cluster (TD-OCC) method for first-principles simulations of high-field phenomena such as tunneling ionization and…

Chemical Physics · Physics 2022-11-21 Takeshi Sato , Himadri Pathak , Yuki Orimo , Kenichi L. Ishikawa

We report the formulation of a new, cost-effective approximation method in the time-dependent optimized coupled-cluster (TD-OCC) framework [T. Sato et al., J. Chem. Phys. 148, 051101 (2018)] for first-principles simulations of multielectron…

Chemical Physics · Physics 2022-08-11 Himadri Pathak , Takeshi Sato , Kenichi L. Ishikawa

We compute nuclear response functions by solving the time-dependent A-body Schr\"odinger equation, recording the time-dependent transition moment and extracting spectral information via Fourier transforms. The solution of the time-dependent…

We investigate the numerical stability of time-dependent coupled-cluster theory for many-electron dynamics in intense laser pulses, comparing two coupled-cluster formulations with full configuration interaction theory. Our numerical…

Time-dependent coupled-cluster method with time-varying orbital functions, called time-dependent optimized coupled- cluster (TD-OCC) method, is formulated for multielectron dynamics in an intense laser field. We have successfully derived…

Chemical Physics · Physics 2018-03-14 Takeshi Sato , Himadri Pathak , Yuki Orimo , Kenichi L. Ishikawa

In order to explore the effects of high levels of electron correlation on the real-time coupled cluster formalism and algorithmic behavior, we introduce a time-dependent implementation of the CC3 singles, doubles and approximate triples…

Chemical Physics · Physics 2025-01-23 Zhe Wang , Håkon Emil Kristiansen , Thomas Bondo Pedersen , T. Daniel Crawford

Multivariate time series (MTS) analysis prevails in real-world applications such as finance, climate science and healthcare. The various self-attention mechanisms, the backbone of the state-of-the-art Transformer-based models, efficiently…

Machine Learning · Computer Science 2023-11-21 Quang Minh Nguyen , Lam M. Nguyen , Subhro Das

Real-time propagation methods for chemistry and physics are invariably formulated using variational techniques. The time-dependent bivariational principle (TD-BIVP) is known to be the proper framework for coupled-cluster type methods, and…

We report the implementation of a cost-effective approximation method within the framework of time-dependent optimized coupled-cluster (TD-OCC) method [J. Chem. Phys. 148, 051101 (2018)] for real-time simulations of intense laser-driven…

Chemical Physics · Physics 2020-04-22 Himadri Pathak , Takeshi Sato , Kenichi L. Ishikawa

A time-dependent vibrational electronic coupled-cluster (VECC) approach is proposed to simulate photoelectron/ UV-VIS absorption spectra, as well as time-dependent properties for non-adiabatic vibronic models, going beyond the…

Chemical Physics · Physics 2023-12-25 Songhao Bao , Neil Raymond , Marcel Nooijen

We present a time-dependent extension of logarithmic perturbation theory for nonrelativistic quantum dynamics governed by the Schr\"odinger equation, in which the logarithm of the wave function is expanded in powers of a coupling constant.…

Quantum Physics · Physics 2026-04-17 Juan Carlos del Valle , Paul Bergold , Karolina Kropielnicka

We derive a time-dependent density functional theory appropriate for calculating the near-edge X-ray absorption spectrum in molecules and condensed matter. The basic assumption is to increase the space of many-body wave functions from one…

Strongly Correlated Electrons · Physics 2015-06-16 G. F. Bertsch , A. Lee
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