Interactions between charged surfaces mediated by molecules with spatially distributed charges

2012 ◽  
Vol 85 (1) ◽  
pp. 15-26 ◽  
Author(s):  
Klemen Bohinc
Keyword(s):  
Density Functional ◽  
Mean Field Theory ◽  
Mean Field ◽  
Short Review ◽  
Molecular Shape ◽  
Attractive Force ◽  
Charge Densities ◽  
Charged Surfaces ◽  
Spatially Distributed ◽  
Rigid Rod

A short review of recent theoretical advances in studies of the interaction between highly charged systems is presented. Such a system could not be described by the mean field theory. More advanced methods have to be used in order to introduce the correlations between highly charged particles. In this work I focus on the system of highly charged surfaces, separated by a solution of molecules with spatially distributed charge. Two different representations of the molecular shape will be considered: rod-like and spherical. The system will be theoretically described by the density functional theory. For sufficiently long molecules and large surface charge densities, an attractive force between like-charged surfaces arises due to the spatially distributed charges within the molecules. The added salt has influence on the condition for the attractive force between like-charged surfaces. The theoretical results will be compared with Monte Carlo (MC) simulations. Recent measurements with multivalent rigid rod-like particles will be discussed.

scholarly journals Single Chain Mean-Field Theory Study on Responsive Behavior of Semiflexible Polymer Brush

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 778
Author(s):  
Yingli Niu ◽  
Xiangyu Bu ◽  
Xinghua Zhang
Keyword(s):  
Field Theory ◽  
Message Passing Interface ◽  
Mean Field Theory ◽  
Mean Field ◽  
Algorithmic Complexity ◽  
Ensemble Average ◽  
Single Chain ◽  
Metropolis Monte Carlo ◽  
Rigid Rod ◽  
Chain Conformations

The application of single chain mean-field theory (SCMFT) on semiflexible chain brushes is reviewed. The worm-like chain (WLC) model is the best mode of semiflexible chain that can continuously recover to the rigid rod model and Gaussian chain (GC) model in rigid and flexible limits, respectively. Compared with the commonly used GC model, SCMFT is more applicable to the WLC model because the algorithmic complexity of the WLC model is much higher than that of the GC model in self-consistent field theory (SCFT). On the contrary, the algorithmic complexity of both models in SCMFT are comparable. In SCMFT, the ensemble average of quantities is obtained by sampling the conformations of a single chain or multi-chains in the external auxiliary field instead of solving the modified diffuse equation (MDE) in SCFT. The precision of this calculation is controlled by the number of bonds Nm used to discretize the chain contour length L and the number of conformations M used in the ensemble average. The latter factor can be well controlled by metropolis Monte Carlo simulation. This approach can be easily generalized to solve problems with complex boundary conditions or in high-dimensional systems, which were once nightmares when solving MDEs in SCFT. Moreover, the calculations in SCMFT mainly relate to the assemble averages of chain conformations, for which a portion of conformations can be performed parallel on different computing cores using a message-passing interface (MPI).

scholarly journals Investigation of the nuclear structure of 84-108Mo isotopes using Skyrme-Hartree-Fock method

2019 ◽  
Vol 13 (26) ◽  
pp. 1-11
Author(s):  
Ali A. Alzubadi
Keyword(s):  
Density Functional ◽  
Good Description ◽  
Mean Field ◽  
Nucleon Nucleon ◽  
Effective Density ◽  
Skin Thickness ◽  
Neutron Skin ◽  
Energy Density Functional ◽  
Charge Densities ◽  
Hartree Fock

Over the last few decades the mean field approach using selfconsistentHaretree-Fock (HF) calculations with Skyrme effectiveinteractions have been found very satisfactory in reproducingnuclear properties for both stable and unstable nuclei. They arebased on effective energy-density functional, often formulated interms of effective density-dependent nucleon–nucleon interactions.In the present research, the SkM, SkM*, SI, SIII, SIV, T3, SLy4,Skxs15, Skxs20 and Skxs25 Skyrme parameterizations have beenused within HF method to investigate some static and dynamicnuclear ground state proprieties of 84-108Mo isotopes. In particular,the binding energy, proton, neutron, mass and charge densities andcorresponding root mean square radius, neutron skin thickness andcharge form factor are calculated by using this method with theSkyrme parameterizations mentioned above. The calculated resultsare compared with the available experimental data. Calculationsshow that the Skyrme–Hartree–Fock (SHF) theory with aboveforce parameters provides a good description on Mo isotopes.

Multiscale Simulations of Domains in Ferroelectrics

Domain Walls ◽  
2020 ◽  
pp. 311-339
Author(s):  
S. Liu ◽  
I. Grinberg ◽  
A. M. Rappe
Keyword(s):  
Density Functional ◽  
Large Scale ◽  
Mean Field Theory ◽  
Mean Field ◽  
Md Simulations ◽  
Relaxor Ferroelectrics ◽  
Ferroelectric Materials ◽  
Multiscale Simulations ◽  
Challenges And Opportunities ◽  
Physically Based

This chapter focuses on recent studies of ferroelectrics, where large-scale molecular dynamics (MD) simulations using first-principles-based force fields played a central role in revealing important physics inaccessible to direct density functional theory (DFT) calculations but critical for developing physically-based free energy functional for coarse-grained phase-field-type simulations. After reviewing typical atomistic potentials of ferroelectrics for MD simulations, the chapter describes a progressive theoretical framework that combines DFT, MD, and a mean-field theory. It then focuses on relaxor ferroelectrics. By examining the spatial and temporal polarization correlations in prototypical relaxor ferroelectrics with million-atom MD simulations and novel analysis techniques, this chapter shows that the widely accepted model of polar nanoregions embedded in a non-polar matrix is incorrect for Pb-based relaxors. Rather, the unusual properties of theses relaxor ferroelectrics stem from the presence of a multi-domain state with extremely small domain sizes (2–10 nanometers), giving rise to a greater flexibility for polarization rotations and the ultrahigh dielectric and piezoelectric responses. Finally, this chapter discusses the challenges and opportunities for multiscale simulations of ferroelectric materials.

Nature of Non-magnetic Strongly-Correlated State in Plutonium

2006 ◽  
Vol 986 ◽  
Author(s):  
Leniod Purovskii ◽  
Alexander Shick ◽  
Ladislav Havela ◽  
Mikhail Katsnelson ◽  
Alexander Lichtenstein
Keyword(s):  
Field Theory ◽  
Density Functional ◽  
Local Density ◽  
Mean Field Theory ◽  
Mean Field ◽  
Dynamical Mean Field Theory ◽  
Cubic Phase ◽  
Face Centered Cubic ◽  
Strongly Correlated ◽  
Starting Point

AbstractLocal density approximation for the electronic structure calculations has been highly successful for non-correlated systems. The LDA scheme quite often failed for strongly correlated materials containing transition metals and rare-earth elements with complicated charge, spin and orbital ordering. Dynamical mean field theory in combination with the first-principle scheme (LDA+DMFT) can be a starting point to go beyond static density functional approximation and include effects of charge, spin and orbital fluctuations. Ab-initio relativistic dynamical mean-field theory is applied to resolve the long-standing controversy between theory and experiment in the “simple” face-centered cubic phase of plutonium called δ-Pu. In agreement with experiment, neither static nor dynamical magnetic moments are predicted. In addition, the quasiparticle density of states reproduces not only the peak close to the Fermi level, which explains the large coefficient of electronic specific heat, but also main 5f features observed in photoelectron spectroscopy.

scholarly journals Strong enhancement of magnetic order from bulk to stretched monolayer FeSe as Hund’s metals

2020 ◽  
Vol 6 (1) ◽  
Author(s):  
Chang-Youn Moon
Keyword(s):  
Density Functional ◽  
Magnetic Order ◽  
Mean Field Theory ◽  
Mean Field ◽  
Comprehensive Understanding ◽  
Functional Theory ◽  
Iron Based Superconductors ◽  
Magnetic Orders ◽  
Spatial Isolation ◽  
Iron Based

Abstract Despite of the importance of magnetism in possible relation to other key properties in iron-based superconductors, its understanding is still far from complete especially for FeSe systems. On one hand, the origin of the absence of magnetic orders in bulk FeSe is yet to be clarified. On the other hand, it is still not clear how close monolayer FeSe on SrTiO3, with the highest transition temperature among iron-based superconductors, is to a magnetic instability. Here we investigate magnetic properties of bulk and monolayer FeSe using dynamical mean-field theory combined with density-functional theory. We find that suppressed magnetic order in bulk FeSe is associated with the reduction of interorbital charge fluctuations, an effect of Hund’s coupling, enhanced by a larger crystal-field splitting. Meanwhile, spatial isolation of Fe atoms in expanded monolayer FeSe leads into a strong magnetic order, which is completely destroyed by a small electron doping. Our work provides a comprehensive understanding of the magnetic order in iron-based superconductors and other general multi-orbital correlated systems as Hund’s metals.

scholarly journals BEYOND DENSITY FUNCTIONAL THEORY: THE DOMESTICATION OF NONLOCAL POTENTIALS

2004 ◽  
Vol 18 (02n03) ◽  
pp. 73-82 ◽  
Author(s):  
ROBERT K. NESBET
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Correlation Energy ◽  
Mean Field Theory ◽  
Mean Field ◽  
Energy Functional ◽  
Functional Theory ◽  
Large Molecules ◽  
Cellular Method ◽  
Nonlocal Potentials

Due to efficient scaling with electron number N, density functional theory (DFT) is widely used for studies of large molecules and solids. Restriction of an exact mean-field theory to local potential functions has recently been questioned. This review summarizes motivation for extending current DFT to include nonlocal one-electron potentials, and proposes methodology for implementation of the theory. The theoretical model, orbital functional theory (OFT), is shown to be exact in principle for the general N-electron problem. In practice it must depend on a parametrized correlation energy functional. Functionals are proposed suitable for short-range Coulomb-cusp correlation and for long-range polarization response correlation. A linearized variational cellular method (LVCM) is proposed as a common formalism for molecules and solids. Implementation of nonlocal potentials is reduced to independent calculations for each inequivalent atomic cell.

Metal-Oxygen Hybridization and Core-Level Spectra in Actinide and Rare-Earth Oxides

MRS Advances ◽  
2016 ◽  
Vol 1 (44) ◽  
pp. 3007-3012 ◽  
Author(s):  
Jindřich Kolorenč
Keyword(s):  
Rare Earth ◽  
Density Functional ◽  
Mean Field Theory ◽  
Mean Field ◽  
Core Level ◽  
Dynamical Mean Field Theory ◽  
Functional Theory ◽  
The Core ◽  
The Density Functional Theory ◽  
Rare Earth Sesquioxides

ABSTRACT We employ a combination of the density-functional theory and the dynamical mean-field theory to study the electronic structure of selected rare-earth sesquioxides and dioxides. We concentrate on the core-level photoemission spectra, in particular, we illustrate how these spectra reflect the integer or fractional filling of the 4f orbitals. We compare the results to our earlier calculations of actinide dioxides and analyze why the core-level spectra of actinide compounds display a substantially reduced sensitivity to the filling of the 5f orbitals.

THE MOTT TRANSITION AND F ELECTRON PHYSICS

2003 ◽  
Vol 17 (28) ◽  
pp. 5101-5109 ◽  
Author(s):  
GABRIEL KOTLIAR ◽  
SERGEJ Y. SAVRASOV
Keyword(s):  
Field Theory ◽  
Spectral Density ◽  
Density Functional ◽  
Mean Field Theory ◽  
Mean Field ◽  
Mott Transition ◽  
Functional Approach ◽  
Dynamical Mean Field Theory ◽  
Quantitative Results ◽  
Actinide Series

We revisit the issue of the Mott transition across the actinide series from the perspective of the spectral density functional approach to realistic dynamical mean-field theory. We stress both qualitative insights from the connection with models and quantitative results.

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