Questions tagged [density-functional-theory]

For questions about simulations using Density Functional Theory.

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10
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1answer
82 views

When running DFT on Q-Chem with an HPC cluster, why is parallelization with OpenMP faster than with MPI?

How to maximize the efficiency/time-to-solution of the calculations in Q-Chem on HPC clusters? MPI parallelization is supposed to improve time-to-solution as compared to OpenMP. The system I tested ...
17
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1answer
193 views

How does the mBJ potential give an accurate band gap as compared to LDA and GGA?

I am not able to understand the literature on how the modified Becke-Johnson(MBJ)$^{[1]}$ potential gives an accurate bandgap. Can someone please help? Thank you. The formula for the potential can be ...
16
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1answer
91 views

How to ensure a smooth band structure?

I performed an HSE06 calculations using VASP and the calculated band gap is in good agreement with experiment. However the band is not smooth, with very sharp, zig-zag like features. How to improve ...
13
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1answer
120 views

How to make heterostructure/heterojunction structure?

How can I make a heterostructure or a heterojunction of ZnO/MgZnO for optimization with WIEN2k code?
17
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1answer
116 views

Why is the band structure of a supercell more dense than for simple cell?

In order to do DFT calculations of metallic alloys, the start point is a supercell, whose atoms are changed to match the desired stoichiometry. Gold and Silver, for example, both have FCC structure. ...
12
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3answers
155 views

Is there a repository for DFT pre/postprocessing scripts?

While DFT calculations are a key step in a simulation workflow, generally more steps are required to obtain a meaningful result. This can include pre/post-processing of results to e.g. compute ...
12
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3answers
93 views

Physically motivated double hybrid DFT?

This question came to mind while writing another question here Extended Hybrid Methods, but I felt it was distinct enough to ask separately. In double hybrids DFT methods, you essentially perform a ...
9
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1answer
43 views

Extended Hybrid Methods

Hybrid DFT methods, where the functional is supplemented with Hartree-Fock exchange, have become increasingly popular due to their low cost and decent accuracy. Double hybrids, which mix in an MP2 ...
10
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1answer
71 views

How reproducible are results from materials modelling? Are there any notable results which could not be reproduced?

One of the key pillars of scientific method is the reproducibility of scientific results. A 2016 survey by Nature revealed that many fields in science suffer from reproducibility crisis. Lejaeghere ...
16
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4answers
157 views

Do eigenvalues in DFT mean anything?

My question is specifically related to the molecular energies of Kohn-Sham DFT: Do eigenvalues in KS-DFT mean anything?
10
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2answers
117 views

How to calculate the effective mass from DFT band calculations?

One of the properties used in Solid State Physics, and specially in semiconductor physics, is the effective mass. It can be calculated from the energy dispersion relationship. The simple form, for ...
12
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1answer
106 views

Justification for use of Screened Functionals

Hybrid density functionals with screened Hartree-Fock exchange at long range have become popular for modeling solids. I'm curious as to what the reasoning is behind this functional form. I understand ...
19
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4answers
229 views

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 ...
15
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1answer
59 views

Are there any ab intio/DFT methods to simulate solubility?

When designing molecules or materials (as drug carriers) in drug design, one important properties is the system solubility. Are there any software that using ab intio/DFT methods can be used to ...
19
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3answers
164 views

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 ...
22
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5answers
351 views

When and Why does Density Functional Theory (DFT) fail?

Every method has its strengths and weaknesses. For instance, a strength of DFT is that is has HF like speeds, but can also account for electron-correlation and this is a pretty big feature since ...
14
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1answer
106 views

Can DFT be considered an ab initio method? [closed]

I have very little experience with DFT, but coming from more of a coupled-cluster background, where the improvements are "systematic", to me it seems that the choice of functional in DFT is somewhat ...
20
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1answer
110 views

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 ...
20
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4answers
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 ...
15
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1answer
131 views

What are good basis sets and functionals for Ni, Cd and Pb?

I will setup a single point energy calculation using Gaussian for a system containing atoms of B-N-Ni, B-N-Pb and B-N-Cd. The system are slabs of boron-nitride [1,2] interacting with those metals. ...
12
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0answers
44 views

What are good references to learn how to model heterostructures using DFT? [closed]

I am interested in modeling heterostructures using DFT. What are some good references to start learning?
17
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3answers
211 views

What are the core numerical routines used in density functional theory?

It looks to me to that many of the things one would do within the framework of density functional theory (DFT) ultimately boil down to solving a generalized eigenvalue problem $Av = \lambda Bv$ where $...
18
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1answer
92 views

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 ...
14
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1answer
67 views

DFT modeling intermolecular interactions

Density Functional Theory based codes evaluate quite successfully intramolecular forces responsible of the atomic bonding. Within this technique one is able to obtain molecular relaxed structures that ...
12
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1answer
107 views

Why is the Nonequilibrium Green’s function (NEGF) method for quantum transport not implemented in plane wave codes like VASP and Quantum Espresso?

DFT codes like Siesta, QuantumATK, Questaal, and Smeagol having localized basis sets have NEGF implementations available. But not in plane wave codes like VASP and Quantum Espresso. Why is it so?
36
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13answers
1k views

What are some recent developments in density functional theory?

In the book Materials Modelling Using Density Functional Theory: Properties and Predictions by Feliciano Giustino, a timeline of milestones in DFT was given for achievements between 1964 and 1996: $$\...
17
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1answer
213 views

Are there problems with the Tran-Blaha modified Becke-Johnson potential (mBJ, a.k.a. TB09) in Quantum ESPRESSO?

I have used the modified Becke-Johnson (mBJ) exchange potential before, as it was developed and implemented in Wien2K by Fabien Tran and Peter Blaha (1). In 2013, Éric Germaneau et al. implemented mBJ ...
11
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1answer
194 views

What are good resources to learn Materials Modeling? [closed]

I wonder if there are any books or resources to start learning Materials modelling using methods density functional theory quantum monte carlo molecular dynamics
17
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1answer
139 views

What are some approaches to modeling charged point defects in materials?

From what I understand, one major issue in modeling charged point defects in materials is the existence of artificial interactions between charged defects and their periodic images. Even when using ...
12
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2answers
175 views

What are the scientific justifications of the binding energy equation?

There are many problems where we want to calculate the binding energy between two systems. Normally, we have a system A, adsorbent (a surface, a nanotube, a protein, etc.), that interact with a system ...
15
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1answer
131 views

What are the pre/post processing tools available for VASP?

I am aware of pyPROCAR and VASPKIT. Are there any other tools supporting VASP
21
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2answers
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 ...
17
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2answers
66 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 ...
28
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2answers
625 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 ...
18
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1answer
76 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
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1answer
81 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 ...
25
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1answer
294 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
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2answers
75 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
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2answers
99 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
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1answer
74 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
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1answer
179 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 ...
15
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1answer
165 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
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1answer
96 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
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1answer
82 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?
18
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1answer
76 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
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1answer
92 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 ...
14
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2answers
105 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?

The SCAN (strongly-constrained and appropriately-normed) meta-GGA constructed in 2015 is the most promising metaGGA which respects all 17 known exact constraints that a meta-GGA can satisfy. What are ...
14
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2answers
94 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 ...
22
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1answer
155 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. ...
23
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3answers
243 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 ...