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Self-consistent-field (SCF) approximations formulated using Hartree-Fock (HF) or Kohn-Sham Density Functional Theory (KS-DFT) both have the potential to yield multiple solutions. However, the formal relationship between multiple solutions…

Chemical Physics · Physics 2021-01-06 Rhiannon A. Zarotiadis , Hugh G. A. Burton , Alex J. W. Thom

We investigate the intermolecular interactions between laser-cooled CaF and Ca, in their ground and excited electronic states, aiming to understand atom-exchange reaction pathways. Using state-of-the-art \textit{ab initio} quantum chemistry…

Atomic Physics · Physics 2025-10-28 Dibyendu Sardar , John L. Bohn

We introduce state-averaging into the method of Monte Carlo configuration interaction (SA-MCCI) to allow the stable and efficient calculation of excited states. We show that excited potential curves for H$_{3}$, including a crossing with…

Chemical Physics · Physics 2014-03-03 J. P. Coe , M. J. Paterson

We consider a system of Gross-Pitaevskii equations in R^2 modelling a mixture of two Bose-Einstein condensates with repulsive interaction. We aim to study the qualitative behaviour of ground and excited state solutions. We allow two…

Analysis of PDEs · Mathematics 2008-09-19 Marco Caliari , Marco Squassina

A multi-reference configuration mixing scheme is used to describe the ground state, characterized by well defined spin and space group symmetry quantum numbers as well as doping fractions $N_{e}/N_{sites}$, of one dimensional Hubbard…

Strongly Correlated Electrons · Physics 2015-06-18 R. Rodríguez-Guzmán , Carlos A. Jiménez-Hoyos , Gustavo E. Scuseria

We report a three-dimensional numerical implementation of multiconfiguration time-dependent Hartree-Fock (MCTDHF) based on a multi-resolution Cartesian grid, with no need to assume any symmetry of molecular structure. We successfully…

Computational Physics · Physics 2016-03-23 Ryohto Sawada , Takeshi Sato , Kenichi L. Ishikawa

The calculation of molecular excited states is critically important to decipher a plethora of molecular properties. In this manuscript, we develop an equation of motion formalism on top of a bi-exponentially parametrized ground state…

Chemical Physics · Physics 2024-01-09 Anish Chakraborty , Pradipta Kumar Samanta , Rahul Maitra

Selected configuration interaction (sCI) methods including second-order perturbative corrections provide near full CI (FCI) quality energies with only a small fraction of the determinants of the FCI space. Here, we introduce both a…

Chemical Physics · Physics 2018-08-09 Yann Garniron , Anthony Scemama , Emmanuel Giner , Michel Caffarel , Pierre-François Loos

Microscopic methods and tools to describe nuclear dynamics have considerably been improved in the past few years. They are based on the time-dependent Hartree-Fock (TDHF) theory and its extensions to include pairing correlations and quantum…

Nuclear Theory · Physics 2018-09-13 C. Simenel , A. S. Umar

A practical electronic structure method in which a two-body functional is the fundamental variable is constructed. The basic formalism of our method is equivalent to Hartree-Fock density matrix functional theory [M. Levy in {\it Density…

Other Condensed Matter · Physics 2008-04-23 Balazs Hetenyi , Andreas W. Hauser

Accurate yet efficient modeling of chemical systems with pronounced static correlation in their excited states remains a significant challenge in quantum chemistry, as most electronic structure methods that can adequately capture static…

Chemical Physics · Physics 2025-03-07 Sylvia J. Bintrim , Kevin Carter-Fenk

The ab-initio many-body method suggested in the preceding paper is applied to the 3d transition metals Fe, Co, Ni, and Cu. We use a linearized muffin-tin orbital calculation to determine Bloch functions for the Hartree one-particle…

Condensed Matter · Physics 2007-05-23 I. Schnell , G. Czycholl , R. C. Albers

In the present letter, it is demonstrated how full configuration interaction (FCI) results in extended basis sets may be obtained to within sub-kJ/mol accuracy by decomposing the energy in terms of many-body expansions in the virtual…

Chemical Physics · Physics 2017-09-15 Janus J. Eriksen , Filippo Lipparini , Jürgen Gauss

The energy and analytic gradient are developed for FMO combined with the Hartree-Fock method augmented with three empirical corrections (HF-3c). The auxiliary basis set approach to FMO is extended to perform pair interaction energy…

Chemical Physics · Physics 2018-08-01 Dmitri G. Fedorov , Jimmy C. Kromann , Jan H. Jensen

The electronically excited states of methylene (CH$_2$), ethylene (C$_2$H$_4$), butadiene (C$_4$H$_6$), hexatriene (C$_6$H$_8$), and ozone (O$_3$) have long proven challenging due to their complex mixtures of static and dynamic…

The method of choice for describing attractive quantum systems is Hartree-Fock-Bogoliubov (HFB) theory. This is a nonlinear model which allows for the description of pairing effects, the main explanation for the superconductivity of certain…

Numerical Analysis · Mathematics 2013-11-08 Mathieu Lewin , Séverine Paul

Due to their diverse nature, the faithful description of excited states within electronic structure theory methods remains one of the grand challenges of modern theoretical chemistry. Quantum Monte Carlo (QMC) methods have been applied very…

Chemical Physics · Physics 2020-06-05 Anthony Scemama , Michel Caffarel , Anouar Benali , Denis Jacquemin , Pierre-François Loos

The Dirac-Fock (DF) model replaces the Hartree-Fock (HF) approximation in quantum chemistry when relativistic effects cannot be neglected. Since the Dirac operator is not bounded from below, the notion of ground state is problematic in this…

Analysis of PDEs · Mathematics 2023-12-18 Eric Séré

A shape change of the self-consistent mean-field induced by a configuration change is discussed within the conventional constrained Hartree-Fock (CHF) theory. It is stressed that a single-particle level crossing dynamics should be treated…

Nuclear Theory · Physics 2009-11-10 Lu Guo , Fumihiko Sakata , En-Guang Zhao

Estimating ground state energies of many-body Hamiltonians is a central task in many areas of quantum physics. In this work, we give quantum algorithms which, given any $k$-body Hamiltonian $H$, compute an estimate for the ground state…