Questions tagged [density-functional-theory]

Density functional theory (DFT) is a quantum mechanical model used to estimate the electronic structure of molecules and condensed matter. In broad terms, DFT works by treating all the electrons in the system as a single electron density, and computing physical quantities of interest as functionals of that electron density.

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Confusion on FFT grid size used in ab initio calculations for periodic systems with planewave basis

Sorry it might be a long post, I'll try to write down all my thinking on this topic, and it is appreciated to point out whether and where I make mistakes. We are talking about algorithms used in ...
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Hartree-Fock vs. density functional theory

What is the relationship/difference between the Hartree-Fock method and the density functional theory? It seems the basic formulations of them are very similar.
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Understanding the derivation of the variational principle in classical density functional theory

I am trying to understand the derivation of the variational principle as presented in Bob Evan's 1979 work.[1]. The part that is tripping me up is when he presents the following result. He starts by ...
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How to use Density Functional Theory to get the correct energy spectrum

I'm having some trouble understanding how DFT can be used to obtain results for electronic structure calculations. We can assume that we're studying an $N$ electron atom with a fixed nucleus and want ...
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How to make sense of phonon dispersion curves and dynamic stability?

I've been working on this material that I've been doing DFT calculations on and I've managed to obtain the phonon dispersion curves for it. Calculation for it took quite a while, but here it is: Now ...
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What is the single active electron approximation?

I keep stumbling upon this approximation while reading papers on atomic physics, but I couldn't find a proper description of what it is in any textbook or pedagogical paper. The closest I could find ...
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How to fit Tight-Binding parameters to DFT results in a general situation?

I've been searching for an answer to this for several days and couldn't find what I need. I'm explaining myself: I got the Bandstructure of a MoS2 monolayer using DFT (PBE functionals) and I wanted to ...
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Are electron dipolar spin-spin interactions included in DFT calculations?

I am studying point defects in hBN using Quantum Espresso. It is not clear if electron spin-spin interactions are typically/can be included in DFT calculations. I understand that spin-orbit ...
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Broken symmetry in presence of external confining field

Suppose, there is a many particle system confined by an externally applied field. I have found in books that the system doesn't remain translationally invariant. Can anybody explain why?
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Grand canonical ensemble in describing inhomogeneous fluids

I have seen that in the theories of inhomogeneous fluids classical Density Functional Theory is used, but the treatment is preferably done in Grand Canonical Ensemble. What is the reason for choosing ...
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Expectation Value of an Operator in the Projector Augmented Wave Method

I'm starting on DFT and came across this technique called PAW Wave Method for multi atoms system wave function. It is a widely employed method in DFT calculations. From the attached picture, I'm ...
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How can I easily generate $\rm GaAs$ band structure?

Is there a program where I can easily generate $\rm GaAs$ band structure that shows lowest conduction band valleys?
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The Hund's J - Why can this be quantified?

I was reading on the the implementation of Hubbard 'U' in Density Functional Theory. The Hubbard 'U' can be thought of as a parameter that accounts for the on-site electron-electron interactions in ...
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Mathematical expression of SCAN (Strongly Constrained and Appropriately Normed) constraints in DFT [closed]

Moved to materials stackexchange. I'm compiling the mathematical expression of SCAN (Strongly Constrained and Appropriately Normed) functionals' constraints, but apparently they are not very obvious ...
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