Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

Filter by
Sorted by
Tagged with
21
votes
2answers
217 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 ...
17
votes
2answers
78 views

What are some common techniques for building multiscale models for materials?

Most, if not all, material systems are multiscale in nature that are described by different physics at different length and time scales, ranging from density functional theory (DFT) to phase field ...
29
votes
2answers
768 views

Is there any DFT code or software that has the option to use this exact exchange-correlation energy functional?

Most of the conventional DFT codes or software use LDA, GGA, meta-GGA, PBE, etc. exchange-correlation functionals, but I'm wondering if there is any DFT code or software that uses the new generation ...
21
votes
1answer
104 views

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 ...
15
votes
1answer
96 views

Functionals/basis sets optimized with respect to properties?

In general (at least for molecular calculations) basis sets and DFT functionals are fit to some high level calculation or experimental energy. It is speculated that an accurate energy will result in ...
27
votes
1answer
686 views

Approximate equivalence table between Pople's basis sets and Jensen's DFT optimized polarization consistent basis sets (pcseg-n)

At first I posted this question in chemistry.stackexchange.com, before materials.stackexchange.com was launched in beta. As it went unaswered, I'm giving a try here. I have some calculations results ...
12
votes
2answers
295 views

Which property should be used for a DFT convergence test? Is energy always the best, or should convergence be tested for a different property?

As I pointed out in the other question Convergence test I: same atoms and different structures, each time you start a DFT calculation you need to do a convergence test. Normally, we use the system ...
15
votes
2answers
166 views

In DFT, if I complete a convergence test once, then want to study a different system with the same atoms, do I have to do a new convergence test?

Any time you start a new DFT calculation, it is recommended to do a convergence test. The parameters to include in the tests vary depending on the DFT implementation, i.e. plane-waves, Gaussian basis ...
10
votes
1answer
95 views

Hexagonal lattice optimization

I have downloaded POSCAR file for "WS2" from "materials project website". I want to do lattice optimization, draw "Energy versus lattice parameters" curves, and calculate Bulk modulus through Birch–...
17
votes
1answer
228 views

What is the difference between BDFT and CDFT (magnetic-field DFT and current DFT)?

Following the previous discussion on DFT in strong fields, I would like to ask about the difference between those two alternatives (BDFT and CDFT). By CDFT I do not mean (constrained DFT, but current ...
16
votes
1answer
205 views

How can reactivity indices be calculated in a time-dependent scheme?

Many reactivity descriptors can be obtained from ground state (or static) DFT as energy derivatives respect to the number of electrons, $N$, and the external potential, $v(\mathbf{r})$, like chemical ...
15
votes
1answer
135 views

What makes PBE the most preferred functional over other GGA functionals?

There are many GGA functionals like PW91, PBE, and BLYP. However the most popular functional is the PBE. What is the reason PBE functional so popular?
15
votes
1answer
172 views

Are there any cases where LDA/GGA overestimates band gaps? If so what is the reason?

It is well known that LDA/GGA often underestimates band gaps. So I wonder if there are any cases where LDA/GGA overestimates the band gap? In these cases, what is the reason?
19
votes
1answer
113 views

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 ...
16
votes
1answer
188 views

How to construct a Tight-Binding Hamiltonian from first-principles computations?

Effective Hamiltonian approaches such as the Tight-Binding method played a central role in the reconciliation between chemistry and in physics in the solid state. A classical and complete treatment of ...
16
votes
2answers
189 views

The SCAN meta-GGA respects all 17 known exact constraints that a meta-GGA can satisfy. What are these constraints? What's the significance?

Related question: Mathematical expression of SCAN (Strongly Constrained and Appropriately Normed) constraints in DFT The SCAN (strongly-constrained and appropriately-normed) meta-GGA constructed in ...
14
votes
2answers
109 views

Appropriate functionals for prediction of NMR spectra of transition metal compounds

In line with this question, I'm looking for suitable functionals for transition metal compounds with organic ligands to predict NMR spectra. Also, I'd like some guidelines about how to choose ...
23
votes
1answer
370 views

What are good ways to reduce computing time when working with large systems in VASP?

I know that parallelization is an important factor, however, I wanted to know if there are any other methods of reducing computing time when dealing with large systems without sacrificing accuracy. ...
25
votes
3answers
391 views

What is the largest material that has been studied using density functional theory?

Quantum-chemical calculations are quite expensive with a cost that scales greatly with the number of atoms in the system. What is the largest material that has been modeled using density functional ...
30
votes
3answers
490 views

What are the positives and negatives of periodic DFT codes that don't use plane-wave basis sets?

Most periodic density functional theory (DFT) codes use plane-wave basis sets in conjunction with three-dimensional periodic boundary conditions. In contrast, for molecular systems of finite size, ...
21
votes
1answer
143 views

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 ...
23
votes
4answers
332 views

Available methods and codes for materials discovery / crystal structure prediction?

There are many open databases and projects that allow you to access computed crystal structures of experimentally known compounds, registered in the Inorganic Crystal Structure Database (ICSD). These ...
20
votes
3answers
355 views

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 ...
18
votes
3answers
222 views

How trustworthy is the Tran-Blaha modified Becke-Johnson potential and how does it perform across basis sets?

When modeling solid-state materials and particularly semiconductors, one must go beyond LDA and GGA. One alternative is to use hybrid functionals or the $GW$ method. However, this can be very ...
17
votes
3answers
229 views

When should I include semi-core electrons in DFT calculations?

Many DFT codes use pseudopotentials (for the core electrons) and basis set functions (for the valence electrons) in order to solve the Schrodinger equation. This because simulates each electron ...
19
votes
3answers
518 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.
29
votes
3answers
280 views

Why does orbital-free DFT scale linearly with system size?

In answering another question here (Is there any relevant DFT formalism apart from the Kohn-Sham approach?), I came across numerous statements that Orbital-Free DFT should scale linearly with system ...
16
votes
2answers
81 views

The upper limit for the atomic adsorption energy value on a slab surface?

I want to adsorb atomic oxygen on a slab surface. The adsorption energy I am calculating is around -10 eV. Which seems higher to me than I expected. My question is this: Is this value reasonable ...
25
votes
2answers
270 views

What are the best functionals for transition metal compounds?

Some properties of transition metal compounds can be influenced by static correlation, relativistic effects, and, in some cases, close-lying electronic states could result in difficulties in SCF ...
18
votes
1answer
346 views

In VASP, how is the chemical potential of elements calculated?

I would like to calculate the chemical potential of elements having different environmental condition (rich or poor) using VASP. How is this accomplished?
23
votes
3answers
863 views

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 $U$. ...
18
votes
1answer
611 views

Are there differences in accuracy and reliability between the frozen phonon method and Density Functional Perturbation Theory?

When proposing or predicting new materials, whether in the bulk or in two dimensions, it is important to discuss the stability of the system. This is usually done through thermodynamics and(or) ...
17
votes
2answers
150 views

Is there any relevant DFT formalism apart from the Kohn-Sham approach?

I wonder if all DFT codes are based on the Kohn-Sham formalism?. If other methods are available, what are their scopes?
36
votes
5answers
865 views

Why do we have so many DFT codes (softwares)? Are they redundant?

Lejaeghere et. al studied reproducibility of DFT codes (softwares) by comparing 15 different codes employing 40 different potentials. The study concluded that most codes agree very well, with ...
16
votes
1answer
119 views

k-points convergence for special quasirandom structures (SQS) of the same material containing different # of atoms

For an ordered crystal, we generally converge the k-mesh resolution for a primitive cell or other smaller supercells. We then use this resolution for any other size of the supercell for the same ...
22
votes
2answers
260 views

What are the different ways of calculating dispersion constants?

There are many different dispersion corrections out there. The most famous is D3 [1] (and the new D4 [2]), but there's probably other approaches too. The dispersion energy can be written as: $$ E_{\...
18
votes
1answer
172 views

Exchange-Correlation Two-Electron Integrals

Do any freely available or proprietary electronic structure packages explicitly compute two-electron exchange correlation integrals? I have found a few derivations to calculate excited state ...
17
votes
1answer
118 views

How to evaluate spin exchange parameters of a magnetic material using DFT?

I think we have to calculate total energies using different FM, AFM configurations and solve a set of linear equations. How to arrive at the set of equations for any given structure? An example from ...
8
votes
0answers
102 views

What are the main mathematical approaches to materials modeling? [closed]

What are the main mathematical approaches to materials modeling? This can include both analytical (closed-form) and numerical techniques.
31
votes
1answer
396 views

What correlation effects are included in DFT?

In wavefunction methods the accuracy of the description of a system of electrons can be improved systematically starting from a reference, usually a Hartree-Fock wavefunction. This difference between ...
43
votes
4answers
711 views

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 ...

1
7 8 9 10
11