Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

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What is the closest thing we have to “the” universal density functional?

It is understood that finding "the" universal functional is an NP-complete problem. However, progressively better functionals have been constructed decade after decade and fitted to more and more ...
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How do you calculate the “true” chemical potential in classical density functional theory?

In classical density functional theory, one traditionally calculates the chemical potential by taking the variational derivative, \mu_{i} = \frac{\delta F}{\delta \rho_{i}} \end{...
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How to write my own density functional theory (DFT) code in Python?

I am a DFT user and at some point in the future, I would like to write my own DFT code in Python to help gain a deeper understanding of DFT. As mentioned in a previous answer people have written their ...
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Create a new DFT functional from experimental data

This is my first time here and I think you can help me. I would like to try (just for fun) to create a new DFT functional starting from experimental data. Do you have any manual, procedure or ...
153 views

In DFT, while studying a system using different exchange-correlation functional approximations, are we expected to check convergence for each method?

As pointed out in a previous question each time you start a new DFT calculation, it is recommended to do a convergence test. If I am studying a system using different exchange correlation functional ...
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Given that Kohn-Sham DFT is strictly a ground-state method (at 0 K), how is it sufficient to describe materials in real-life applications?

Kohn-Sham DFT appears to be so popular even though it is strictly a ground-state method - all calculations are done at 0 K. How then, is it so popular when describing materials that have real-life ...
258 views

Difficult cases for converging Kohn-Sham SCF calculations

In a recent article by Woods et. al.[1] a couple of methods for converging ground-state Kohn-Sham DFT calculations are reviewed and compared. In their test suite they give plenty of examples for badly ...
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Meaning of atomic positional parameters

I am trying to model some materials with DFT, so I intended to start out with the structure. However, some texts that present XRD data, use a term called atomic positional parameter. I can't seem to ...
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What are some materials discovered from first-principles calculations that ended up being incorporated in a commercial product?

High-throughput computational screening, inverse materials design, and advances in machine learning have really accelerated the pace in which we can identify novel materials for a wide range of ...
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What is the importance of electron interaction on dielectric response of crystals?

After obtaining the Kohn-Sham orbitals from a plane-wave-based self-consistent-field calculation, the dipole matrix elements could be calculated in order to determine electro-optical properties such ...
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What are the pitfalls for new users of DFT?

This question is inspired from a post in another SE. Many users these days use density functional theory codes as 'black boxes' and hence its natural to expect that they would have made many mistakes ...
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What is the status of graphics processing units in plane-wave DFT?

A few years back, I performed a few calculations of metallic slabs using VASP and the Atomic Simulation Environment (ASE). I'm by no means an expert, but I noticed that the calculations were very CPU ...
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What is the appropriate way of determining a value for the Hubbard-like potential U for LDA+U / GGA+U calculations?

It is known that neither LDA or GGA correctly account for the strong on-site Coulomb interaction of localized electrons[1]. A cost-effective way of correcting this is by using a Hubbard-like term $U$. ...
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How to “get my feet wet” in Density Functional Theory by simulating a water molecule using Python

I just saw I am a beginner in Density Functional Theory. What are some resources that could help me to learn the basics? and it reminded me that few years ago I'd asked How can I calculate the charge ...
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Norm-Conserving or Ultrasoft, which pseudopotential to choose?

Ultrasoft pseudopotential (USPP), in general, requires a lower energy-cutoff to the plane waves when compared to Norm-Conserving ones (NC). On the other hand (at least with Quantum ESPRESSO) the ...
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Physical/Intuitive picture for DFT that all motions and pair correlations in a many-electron system are contained in the total electron density alone

Quoting Becke [1] Density-functional theory (DFT) is a subtle, seductive, provocative business. Its basic premise, that all the intricate motions and pair correlations in a many-electron system are ...
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Hexagonal lattice volume EOS fit

I have a little problem concerning hexagonal volume fitting using VASP. I have followed these steps: Relax the structure from a given volume using ISIF =4 Copy ...
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Cancellation of Errors in density functional approximations or any wavefunction based methods

I am curious to find references for when is it TRUE that the error cancellation in approximate methods like DFT/MP2/etc. are valid and when they fall apart. For example: My understanding is (please ...
262 views

Are there any online course/video lectures available on Density functional theory?

Please mention good online video lectures on theoretical foundations and practical implementation of DFT.
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How to do periodic DFT calculations using Quantum ESPRESSO?

I have only done quantum mechanical computations using non-periodic wavefunctions. I'd like to try to periodic-wavefunction density functional theory. Quantum ESPRESSO seems like a good package ...
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Calculating binding energy between two systems

Regarding the calculation of binding energy of molecular absorption on graphene, for which this has been discussed before, the process of calculating $E_{AB}$ is fairly straight forward, i.e., it is ...
206 views

Semi-infinite surfaces for adsorption: a valid approach?

I'm currently trying to surface reaction of small molecules on metal oxides in VASP. Several papers I've read have approached surface energy calculations in a variety of ways. I first began looking at ...
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Are there any High-Throughput studies that aim to discover High Tc superconductors?

High-Throughput materials modeling based on Density Functional Theory has become very popular recently. If, for example, we search "High-Throughput Perovskites" in Google Scholar, we get over ~14,000 ...
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Database or repository with values for the Hubbard potential U?

The Materials Project and other materials databases have a nice periodic table on their home page that allows you to search for compounds. For some materials, they give an empirical $U$ value used to ...
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Mathematical expression of SCAN (Strongly Constrained and Appropriately Normed) constraints in DFT

(This question is originally posted on physics stackexchange, but someone suggested me to post on this site, so there you go) I'm compiling the mathematical expression of SCAN (Strongly Constrained ...
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How established is density functional theory as a tool in drug design?

Motivated by the ongoing COVID-19 pandemic, I am wondering how established density functional theory (DFT) is as a tool/technique in drug design. Drug molecules come in a wide range of sizes from ...