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We describe an efficient algorithm for computing the matrix vector products that appear in the numerical resolution of boundary integral equations in 2 space dimension. This work is an extension of the so-called Sparse Cardinal Sine…

Numerical Analysis · Mathematics 2017-11-22 Martin Averseng

Extended Lagrangian Born-Oppenheimer molecular dynamics [{\em Phys.\ Rev.\ Lett.\ } {\bf 2008}, {\em 100}, 123004] is presented for Hartree-Fock theory, where the extended electronic degrees of freedom are represented by a density matrix,…

Computational Physics · Physics 2020-05-29 Anders M. N. Niklasson

In the nonequilibrium Green's function approach, the approximation of the correlation self-energy at the second-Born level is of particular interest, since it allows for a maximal speed-up in computational scaling when used together with…

Computational Physics · Physics 2019-11-11 Riku Tuovinen , Fabio Covito , Michael A. Sentef

We develop a method to reconstruct, from measured displacements of an underlying elastic substrate, the spatially dependent forces that cells or tissues impart on it. Given newly available high-resolution images of substrate displacements,…

Quantitative Methods · Quantitative Biology 2018-01-22 Joshua C. Chang , Yanli Liu , Tom Chou

We propose a new mean-field-type framework which can treat the strong correlation induced by the tensor force. To treat the tensor correlation we break the charge and parity symmetries of a single-particle state and restore these symmetries…

Nuclear Theory · Physics 2009-11-10 Satoru Sugimoto , Kiyomi Ikeda , Hiroshi Toki

An implementation of the Hartree-Fock (HF) method capable of robust convergence for well-behaved arbitrary central potentials is presented. The Hartree-Fock equations are converted to a generalized eigenvalue problem by employing a B-spline…

Atomic Physics · Physics 2021-08-13 D. T. Waide , D. G. Green , G. F. Gribakin

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

The tree code for the approximate evaluation of gravitational forces is extended and substantially accelerated by including mutual cell-cell interactions. These are computed by a Taylor series in Cartesian coordinates and in a completely…

Astrophysics · Physics 2009-10-31 Walter Dehnen

The recursive polynomial expansion for construction of a density matrix approximation with rigorous error control [J. Chem. Phys. 128, 074106 (2008)] is implemented in the quantum chemistry program Ergo [SoftwareX 7, 107 (2018)] using the…

Computational Physics · Physics 2019-09-30 Anastasia Kruchinina , Elias Rudberg , Emanuel H. Rubensson

Configuration-space matrix elements of N-body potentials arise naturally and ubiquitously in the Ritz-Galerkin solution of many-body quantum problems. For the common specialization of local, finite-range potentials, we develop the eXact…

This work proposes an efficient numerical approach for compressing a high-dimensional discrete distribution function into a non-negative tensor train (NTT) format. The two settings we consider are variational inference and density…

Numerical Analysis · Mathematics 2025-07-30 Xun Tang , Rajat Dwaraknath , Lexing Ying

The self-energy of the Dirac Brueckner-Hartree-Fock calculation in nuclear matter is parametrized by introducing density-dependent coupling constants of isoscalar mesons in the relativistic Hartree-Fock (RHF) approach where isoscalar meson…

Nuclear Theory · Physics 2009-10-28 Hua-lin Shi , Bao-qiu Chen , Zhong-yu Ma

The Born-Oppenheimer (BO) approximation is less accurate in the presence of a strong magnetic field than in the absence of a field. This is due to the complicated and unpredictable response of electronic structure to the field, especially…

Chemical Physics · Physics 2023-03-29 Tanner Culpitt , Laurens D. M. Peters , Erik I. Tellgren , Trygve Helgaker

This work was originally published by the author in 1999 in a book [1] and later became part of the author's doctoral thesis in 1999 [2]. Since the original language of these works is not English, the author provides a translation of the…

Spectral Theory · Mathematics 2023-06-28 Ilgis Ibragimov

For molecules and solids, we developed efficient MPI-parallel algorithms for evaluating the second-order exchange term with bare, statically screened, and dynamically screened interactions. We employ the resulting term in a fully…

Strongly Correlated Electrons · Physics 2024-12-30 Pavel Pokhilko , Chia-Nan Yeh , Miguel A. Morales , Dominika Zgid

We investigate the existence of holomorphic Hartree-Fock solutions using a revised SCF algorithm. We use this algorithm to study the Hartree-Fock solutions for H$_{2}$ and H$_{4}^{2+}$ and report the emergence of holomorphic solutions at…

Chemical Physics · Physics 2015-11-20 Hugh G. A. Burton , Alex J. W. Thom

Recent measurements of the force versus extension curves in stretched single stranded DNA, under conditions where the hydrogen bonding between complementary bases is inhibited, provide a new handle for the study of self-avoiding effects in…

Condensed Matter · Physics 2007-05-23 C. Bouchiat

We apply the Tensor-Backflow method to investigate the Fermi-Hubbard model on two-dimensional lattices up to 256 sites, exploring various interaction strengths $U$, electron fillings $n$, next-nearest-neighbor hopping $t'$, and boundary…

Strongly Correlated Electrons · Physics 2026-03-27 Xiao Liang

We use the method of Lightcone Conformal Truncation (LCT) to obtain form factors and spectral densities of local operators $\mathcal{O}$ in $\phi^4$ theory in two dimensions. We show how to use the Hamiltonian eigenstates from LCT to obtain…

High Energy Physics - Theory · Physics 2022-05-11 Hongbin Chen , A. Liam Fitzpatrick , Denis Karateev

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