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We study several approaches to orbital optimization in selected configuration interaction plus perturbation theory (SCI+PT) methods, and test them on the ground and excited states of three molecules using the semistochastic heatbath…

Chemical Physics · Physics 2021-07-14 Yuan Yao , C. J. Umrigar

In this work we demonstrate how to compute the one- and two-body reduced density matrices within the spin-adapted full configuration interaction quantum Monte Carlo (FCIQMC) method, which is based on the graphical unitary group approach…

Chemical Physics · Physics 2021-09-27 Werner Dobrautz , Oskar Weser , Nikolay Bogdanov , Ali Alavi , Giovanni Li Manni

Most nonrelativistic electron correlation methods can be adapted to account for relativistic effects, as long as the relativistic molecular spinor integrals are available, from either a four-, two-, or one-component mean-field calculation.…

Strongly Correlated Electrons · Physics 2024-07-17 Zijun Zhao , Francesco A. Evangelista

The convergence property of a stochastic algorithm for the self-consistent field (SCF) calculations of electron structures is studied. The algorithm is formulated by rewriting the electron charges as a trace/diagonal of a matrix function,…

Numerical Analysis · Mathematics 2023-04-20 Taehee Ko , Xiantao Li

Even when starting with a very poor initial guess, the iterative configuration interaction (iCI) approach can converge from above to full CI very quickly by constructing and diagonalizing a small Hamiltonian matrix at each…

Chemical Physics · Physics 2020-01-07 Ning Zhang , Wenjian Liu , Mark R. Hoffmann

In this communication, we represent a self-consistent systematic optimization procedure for the development of optimally tuned (OT) range-separated hybrid (RSH) functionals from \emph{first principles}. This is an offshoot of our recent…

Chemical Physics · Physics 2022-05-24 Abhisek Ghosal , Amlan K. Roy

New density functional theory approach based on a complete active space self-consistent field (CASSCF) reference function in Extended Koopmans' approximation is discussed. Recently, the number of generalizations of density functional theory…

Chemical Physics · Physics 2018-02-15 Sergey Gusarov , Yurii Dmitriev

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

A new framework is presented for evaluating the performance of self-consistent field methods in Kohn-Sham density functional theory. The aims of this work are two-fold. First, we explore the properties of Kohn-Sham density functional theory…

Computational Physics · Physics 2019-07-18 Nick Woods , Phil Hasnip , Mike Payne

High-dimensional and incomplete (HDI) data, characterized by massive node interactions, have become ubiquitous across various real-world applications. Second-order latent factor models have shown promising performance in modeling this type…

Machine Learning · Computer Science 2025-07-08 Jialiang Wang , Junzhou Wang , Xin Liao

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 investigate higher order symplectic integration strategies within Bayesian cosmic density field reconstruction methods. In particular, we study the fourth-order discretisation of Hamiltonian equations of motion (EoM). This is achieved by…

Cosmology and Nongalactic Astrophysics · Physics 2021-09-29 Mónica Hernández-Sánchez , Francisco-Shu Kitaura , Metin Ata , Claudio Dalla Vecchia

Efficient hybrid DFT simulations of solid state materials would be extremely beneficial for computational chemistry and materials science, but is presently bottlenecked by difficulties in computing Hartree-Fock (HF) exchange with plane wave…

Chemical Physics · Physics 2024-10-30 Yuanheng Wang , Diptarka Hait , Pablo A. Unzueta , Juncheng Harry Zhang , Todd J. Martínez

We present model-assisted density fitting (MADF) basis set generator, an algorithm for generating primitive atomic Gaussian density fitting (DF) basis sets (DFBSs) from a contracted Gaussian orbital basis set (OBS). The MADF algorithm…

Chemical Physics · Physics 2025-10-14 Kshitijkumar A. Surjuse , Edward F. Valeev

Best rank-one approximation is one of the most fundamental tasks in tensor computation. In order to fully exploit modern multi-core parallel computers, it is necessary to develop decoupling algorithms for computing the best rank-one…

Numerical Analysis · Mathematics 2024-03-05 Chuanfu Xiao , Zeyu Li , Chao Yang

Complete active space self-consistent field (CASSCF) computations can be realized at polynomial cost via the variational optimization of the active-space two-electron reduced-density matrix (2-RDM). Like conventional approaches to CASSCF,…

Chemical Physics · Physics 2018-12-10 Mohammad Mostafanejad , A. Eugene DePrince

The time-dependent multiconfiguration self-consistent-field method based on the occupation-restricted multiple active space model is proposed (TD-ORMAS) for multielectron dynamics in intense laser fields. Extending the previously proposed…

Atomic Physics · Physics 2015-06-23 Takeshi Sato , Kenichi L. Ishikawa

Fermi-L\"owdin orbital self-interaction-correction (FLOSIC) method uses symmetric orthogonalized Fermi orbitals as localized orbitals in one-electron SIC schemes. In FLOSIC, a set of Fermi orbital descriptors (FOD) that define the FLOs is…

Chemical Physics · Physics 2025-08-08 Selim Romero , Yoh Yamamoto , Tunna Baruah , Rajendra R. Zope

The evaluation of exact (Hartree--Fock, HF) exchange operator is a crucial ingredient for the accurate description of electronic structure in periodic systems through ab initio and hybrid density functional approaches. An efficient…

Chemical Physics · Physics 2020-10-28 Xiao Wang , Cannada A. Lewis , Edward F. Valeev

We present the MCSCF version of density functional theory. Two sets of equations, which correspond to the CI and orbital relaxation respectively, are derived. An important feature is that the correlation potential of DFT for CI wavefunction…

Chemical Physics · Physics 2007-05-23 Shusuke Yamanaka , Koichi Kusakabe , Kazuto Nakata , Toshikazu Takada , Kizashi Yamaguchi