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We use machine learning methods to approximate a classical density functional. As a study case, we choose the model problem of a Lennard Jones fluid in one dimension where there is no exact solution available and training data sets must be…

Soft Condensed Matter · Physics 2019-03-04 Shang-Chun Lin , Martin Oettel

The generalized constrained search formalism is used to address the issues concerning density-to-potential mapping for excited states in time-independent density-functional theory. The multiplicity of potentials for any given density and…

Materials Science · Physics 2015-06-09 Prasanjit Samal , Subrata Jana , Sourabh S. Chauhan

We prove that the electron density function of a real physical system can be uniquely determined by its values on any finite subsystem. This establishes the existence of a rigorous density-functional theory for any open electronic system.…

Quantum Physics · Physics 2007-05-23 Xiao Zheng , Fan Wang , GuanHua Chen

When a fluid is subject to an external field, as is the case near an interface or under spatial confinement, then the density becomes spatially inhomogeneous. Although the one-body density provides much useful information, a higher level of…

Soft Condensed Matter · Physics 2022-07-14 S. M. Tschopp , F. Sammüller , S. Hermann , M. Schmidt , J. M. Brader

The classical Density Functional Theory (DFT) is introduced as an application of entropic inference for inhomogeneous fluids at thermal equilibrium. It is shown that entropic inference reproduces the variational principle of DFT when…

Statistical Mechanics · Physics 2021-09-14 Ahmad Yousefi , Ariel Caticha

In this note, we show that the Local Molecular Field theory of Weeks et. al. can be re-derived as an extremum problem for an approximate Helmholtz free energy. Using the resulting free energy as a classical, fluid density functional yields…

Soft Condensed Matter · Physics 2025-07-15 David M. Rogers

We consider a system of interacting particles subjected to Langevin inertial dynamics and derive the governing time-dependent equation for the one-body density. We show that, after suitable truncations of the…

Statistical Mechanics · Physics 2007-12-17 Umberto Marini Bettolo Marconi , Simone Melchionna

Classical density functional theory for finite temperatures is usually formulated in the grand-canonical ensemble where arbitrary variations of the local density are possible. However, in many cases the systems of interest are closed with…

Statistical Mechanics · Physics 2022-04-06 James F. Lutsko

We establish large deviation principles (LDPs) for empirical measures associated with a sequence of Gibbs distributions on $n$-particle configurations, each of which is defined in terms of an inverse temperature $% \beta_n$ and an energy…

Probability · Mathematics 2020-01-07 Paul Dupuis , Vaios Laschos , Kavita Ramanan

We provide upper and lower bounds on the lowest free energy of a classical system at given one-particle density $\rho(x)$. We study both the canonical and grand-canonical cases, assuming the particles interact with a pair potential which…

Mathematical Physics · Physics 2023-03-29 Michal Jex , Mathieu Lewin , Peter S. Madsen

Density functional theory stems from the Hohenberg-Kohn-Sham-Mermin (HKSM) theorem in the grand canonical ensemble (GCE). However, as recent work shows, although its extension to the canonical ensemble (CE) is not straightforward, work in…

Statistical Mechanics · Physics 2009-11-07 J. A. Hernando

Classical density functional theory (DFT) is the primary method for investigations of inhomogeneous fluids in external fields. It requires the excess Helmholtz free energy functional as input to an Euler-Lagrange equation for the one-body…

Soft Condensed Matter · Physics 2026-02-05 S. M. Tschopp , H. Vahid , J. M. Brader

Based on recent progress on fermionic exchange symmetry we propose a way to develop new functionals for reduced density matrix functional theory. For some settings with an odd number of electrons, by assuming saturation of the inequalities…

Strongly Correlated Electrons · Physics 2018-10-23 Carlos L. Benavides-Riveros , Miguel A. L. Marques

A general formulation of the equilibrium state of a many-electron system in terms of a (mixed-state, ensemble) density matrix operator in the Fock space, based on the maximum entropy principle, is introduced. Various characteristic…

Chemical Physics · Physics 2013-10-28 Robert Balawender , Andrzej Holas

Given a vector space of microscopic quantum observables, density functional theory is formulated on its dual space. A generalized Hohenberg-Kohn theorem and the existence of the universal energy functional in the dual space are proven. In…

Nuclear Theory · Physics 2009-09-25 G. Rosensteel , Ts. Dankova

We present a density functional scheme for calculating the pair density (PD) by means of the correlated wave function. This scheme is free from both of problems related to PD functional theory, i.e., (a) the need to constrain the…

Strongly Correlated Electrons · Physics 2015-06-25 Masahiko Higuchi , Katsuhiko Higuchi

The exact reduced density-matrix functional is derived from the Luttinger-Ward functional of the single-particle Green's function. Thereby, a formal link is provided between diagrammatic many-body approaches using Green's functions on the…

Strongly Correlated Electrons · Physics 2013-12-11 Peter E. Blöchl , Thomas Pruschke , Michael Potthoff

The selection of basic variables in current-density functional theory and formal properties of the resulting formulations are critically examined. Focus is placed on the extent to which the Hohenberg--Kohn theorem, constrained-search…

Materials Science · Physics 2015-06-11 Erik I. Tellgren , Simen Kvaal , Espen Sagvolden , Ulf Ekström , Andrew M. Teale , Trygve Helgaker

Density functional theory, when applied to systems with $T\neq 0$, is based on the grand canonical extension of the Hohenberg-Kohn-Sham theorem due to Mermin (HKSM theorem). While a straightforward canonical ensemble generalization fails,…

Statistical Mechanics · Physics 2009-10-31 J. A. Hernando , L. Blum

This article generalizes the notion of the local density of a many-body system to introduce collective coordinates as explicit degrees of freedom. It is shown that the energy of the system can be expressed as a functional of this object.…

Nuclear Theory · Physics 2014-04-23 Thomas Lesinski