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We calculate the high-harmonic generation (HHG) spectra, strong-field ionization, and time-dependent dipole-moment of Ne using explicitly time-dependent optimized second-order many-body perturbation method (TD-OMP2) where both orbitals and…

Chemical Physics · Physics 2020-08-18 Himadri Pathak , Takeshi Sato , Kenichi L. Ishikawa

In parallel with the evolution of femtosecond and attosecond laser as well as free-electron laser technology, a variety of theoretical methods have been developed to describe the behavior of atoms, molecules, clusters, and solids under the…

Atomic Physics · Physics 2015-11-12 Kenichi L. Ishikawa , Takeshi Sato

Multi-configuration range-separated density-functional theory is extended to the time-dependent regime. An exact variational formulation is derived. The approximation, which consists in combining a long-range…

Chemical Physics · Physics 2013-02-27 Emmanuel Fromager , Stefan Knecht , Hans Jørgen Aa. Jensen

The multiconfiguration time-dependent Hartree-Fock (MCTDHF) method is formulated for treating the coupled electronic and nuclear dynamics of diatomic molecules without the Born- Oppenheimer approximation. The method treats the full…

Computational Physics · Physics 2015-05-27 Daniel J. Haxton , Keith V. Lawler , C. William McCurdy

We apply a three-dimensional (3D) implementation of the time-dependent restricted-active-space self-consistent-field (TD-RASSCF) method to investigate effects of electron correlation in the ground state of Be as well as in its…

Atomic Physics · Physics 2017-06-07 Juan J. Omiste , Wenliang Li , Lars Bojer Madsen

This article examines the time-dependent Hartree-Fock (TDHF) approximation of single-particle dynamics in systems of interacting fermions. We find the TDHF approximation to be accurate when there are sufficiently many particles and the…

Mathematical Physics · Physics 2007-05-23 Claude Bardos , Francois Golse , Alex D. Gottlieb , Norbert J. Mauser

Spectroscopies that probe electronic excitations from core levels into unoccupied orbitals, such as X-ray absorption spectroscopy and electron energy loss spectroscopy, are widely used to gain insight into the electronic and chemical…

Materials Science · Physics 2022-09-12 Marcus Annegarn , Juhan Matthias Kahk , Johannes Lischner

Near-degenerate electronic structures remain a major challenge for conventional single-reference density functional theory (DFT). To address this problem, we propose time-dependent $\Delta$SCF (TD$\Delta$SCF), a novel linear-response scheme…

Chemical Physics · Physics 2026-05-12 Shuto Shibasaki , Fumiya Mohri , Takashi Tsuchimochi

We present a modification of the $\Delta$SCF method of calculating energies of excited states, in order to make it applicable to resonance calculations of molecules adsorbed on metal surfaces, where the molecular orbitals are highly…

Materials Science · Physics 2009-03-06 Jeppe Gavnholt , Thomas Olsen , Mads Engelund , Jakob Schiøtz

We discuss the multispecies time-dependent restricted-active-space self-consistent-field theory, an \textit{ab initio} wavefunction-based theory for mixtures of ultracold atomic and molecular gases. We present the general theory, based on…

Quantum Physics · Physics 2018-08-01 Camille Lévêque , Lars Bojer Madsen

We propose a gauge-invariant formulation of the channel orbital-based time-dependent configuration interaction singles (TDCIS) method [Phys. Rev. A 74, 043420 (2006)], one of the powerful ab initio methods to investigate electron dynamics…

Atomic Physics · Physics 2018-02-09 Takeshi Sato , Takuma Teramura , Kenichi L. Ishikawa

A challenge in modeling time-dependent strong-field processes such as high-harmonic generation for many-body systems, is how to effectively represent the electronic continuum. We apply Rothe's method to the time-dependent Hartree-Fock…

Chemical Physics · Physics 2025-08-22 Simon Elias Schrader , Håkon Emil Kristiansen , Thomas Bondo Pedersen , Simen Kvaal

The time-dependent Hartree-Fock (TDHF) method is an approach to simulate the mean field dynamics of electrons within the assumption that the electrons move independently in their self-consistent average field and within the space of single…

Quantum Physics · Physics 2023-09-06 Sahil Gulania , Stephen K. Gray , Yuri Alexeev , Bo Peng , Niranjan Govind

Despite the variety of available computational approaches, state-of-the-art methods for calculating excitation energies such as time-dependent density functional theory (TDDFT), are computationally demanding and thus limited to moderate…

Chemical Physics · Physics 2022-03-10 Martina Stella , Kritam Thapa , Luigi Genovese , Laura E. Ratcliff

The implementation of an efficient self-consistent field (SCF) method including both scalar relativistic effects and spin-orbit interaction in density functional theory (DFT) is presented. We make use of Gaussian-type orbitals (GTOs) and…

Chemical Physics · Physics 2024-05-03 Yannick J. Franzke , Werner M. Schosser , Fabian Pauly

This article concerns the time-dependent Hartree-Fock (TDHF) approximation of single-particle dynamics in systems of interacting fermions. We find that the TDHF approximation is accurate when there are sufficiently many particles and the…

Quantum Physics · Physics 2015-02-25 Claude Bardos , Francois Golse , Alex D. Gottlieb , Norbert J. Mauser

By simulating the real-time multielectron wavefunction with the multi-configurational time-dependent Hartree-Fock (MCTDHF) approach, we conduct an \textit{ab initio} study of the single-photon ionization process of a body-fixed water…

Atomic Physics · Physics 2026-01-14 Zhao-Han Zhang , Yang Li , Himadri Pathak , Takeshi Sato , Kenichi L. Ishikawa , Feng He

In this manuscript we provide an outline of the numerical methods used in implementing the density constrained time-dependent Hartree-Fock (DC-TDHF) method and provide a few examples of its application to nuclear fusion. In this approach,…

Nuclear Theory · Physics 2015-02-16 V. E. Oberacker , A. S. Umar

We present the theory, implementation, and benchmarking of a real-time time-dependent density functional theory (RT-TDDFT) module within the RMG code, designed to simulate the electronic response of molecular systems to external…

In this work, a derivation and implementation of the relativistic time-dependent configuration interaction singles (RTDCIS) method is presented. Various observables for krypton and xenon atoms obtained by RTDCIS are compared with…

Atomic Physics · Physics 2022-01-12 Felipe Zapata , Jimmy Vinbladh , Anton Ljungdahl , Eva Lindroth , Jan Marcus Dahlström