New answers tagged density-functional-theory
2
votes
Temperature effect on elastic constant using VASP
The following paper is quite nice, in my opinion:
Shang et al., Temperature-dependent elastic stiffness constants of α- and θ-Al2O3 from first-principles calculations, J. Phys. Condens. Matter 22 (...
- 1,718
6
votes
Which formalism is better suited to model a crystal with defects: Hartree–Fock, Kohn–Sham, or something else?
I would like to add a few aspects to the answer of wzkchem5.
Considering local or semilocal xc functionals for the KS equations, one difference between HF and KS is that HF is computationally more ...
- 1,046
7
votes
Which formalism is better suited to model a crystal with defects: Hartree–Fock, Kohn–Sham, or something else?
Let me first clarify a few things.
Whether a calculation is Kohn-Sham or Hartree-Fock has nothing to do with whether the calculation is periodic or not. In fact, both Kohn-Sham and Hartree-Fock can ...
- 6,418
3
votes
Successfully running parallel gas phase calculation on AMD cloud instance but implicit solvent fails (Local Intel workstation successfully runs both)
Turns out the issue is that Fortran is required to run solvent-based calculations in parallel. My cloud instances did not have it installed. Problem was solved after installing Fortran. Answer was ...
- 81
2
votes
What are the types of DFT?
TAO-DFT: Thermally-Assisted-Occupation DFT
J.-D. Chai, J. Chem. Phys. 136, 154104 (2012).
https://aip.scitation.org/doi/10.1063/1.3703894
Even with the exact exchange-correlation energy functional in ...
- 63
3
votes
Raman Spectra in Quantum Espresso
It would seem that if a crystal system has no Raman-active modes, QE simply won't print out the Raman intensities. To verify this, I tried to simulate the Raman activity of $\ce{NaCl}$ (also a member ...
- 91
4
votes
Is there any relation between static correlation and finite-temperature smearing?
You may like to read this 2012 JCP paper to know TAO-DFT:
https://aip.scitation.org/doi/10.1063/1.3703894
Even with the exact exchange-correlation energy functional in KS-DFT, one still needs to ...
- 63
5
votes
Future and limitations of DFT
1 - To what extent is DFT is useful if one wants to understand questions, such as topological quantum computing? Is DFT a good starting point if one is interested in studying aspects of condensed ...
- 3,938
3
votes
DFT code for simulating thousands of atoms in a supercell
Well, maybe you can first specify the calculations you would like to do, given it maybe relaxation/MD; I suggest you start with cheap method like Tight binding DFT with quite efficient parametric as ...
9
votes
DFT code for simulating thousands of atoms in a supercell
To make a recommendation more details are really needed, as noted in the comments. However CRYSTAL (full disclosure - I am an author of the code) has been used for calculations on over a thousand ...
- 522
12
votes
DFT code for simulating thousands of atoms in a supercell
ONETEP https://www.onetep.org/ is a linear-scaling DFT code suitable and efficient for such large simulations. The main purpose of it, in the first place, was to lower the computational cost of ...
- 121
11
votes
Accepted
DFT code for simulating thousands of atoms in a supercell
The SIESTA method and its implementation offer an efficient and flexible simulation paradigm based on the use of strictly localized basis sets, this allows the implementation of reduced scaling ...
- 1,181
6
votes
Accepted
Transiesta output through a single gold atom
With a single atom there might be leakage current. Probably, if you had more Au atoms the transmission would be fully suppressed.
The 4 eV peak is likely close to a van-Hove singularity of the ...
- 1,724
8
votes
Accepted
How to do simulation when two atoms exist in the same coordinate position in the lattice?
You cannot have two atoms at the same coordinate position. The idea behind fraction occupancy is that, in a sufficient large cell, some positions will be occupied "alternated" by two ...
- 18.5k
7
votes
Effective mass of holes was measured using DFT
The easier way to calculate the effective mass ($m^*$) is assuming the band as parabolic and calculate it from the equation below:
$$E(\vec{k}) = E_0 + \frac{\hbar^2\vec{k}^2}{2m^*}$$
This means that $...
- 18.5k
5
votes
Why can't DFT calculate the accurate electronic configuration of the Oxygen atom?
I am unfamiliar with this exact tutorial but this looks fine to me, you have 4 electrons in one spin and 2 in the other, giving a net 2 unpaired electrons. This is correct when you look at the ground ...
- 9,801
5
votes
Accepted
Decide the position of oxygen vacancy via the configuration with the lowest energy?
Introduction
Skip at your own risk
TiO$_2$ has an equilibrium concentration $c_{eq}$ of all symmetry-unique oxygen vacancies, which is given by
$c_{eq} = \frac{N_{O_i}}{N_O} = \exp \left( -\frac{\...
- 836
4
votes
Textbooks for electronic structure theory
I read Electronic Structure Basic Theory and Practical Methods by Richard M. Martin, University of Illinois, Urbana-Champaign. Here is the link Electronic structure
- 1,450
3
votes
Solving the Schrödinger equation as a service?
Good Chemistry
A new company called Good Chemistry, a spinoff company of 1QBit, has released a beta-version of their QEMIST Cloud service which purports to do exactly what you're asking about. From ...
- 503
5
votes
When is coupled cluster preferred over DFT?
Coupled cluster is theoretically more accurate that DFT, as it's limiting behaviour is an exact solution to the Schrödinger equation. By limiting behaviour, I mean including all possible excitations (...
- 503
8
votes
Accepted
Simulating autoionization of small molecules using DFT or AIMD
This is because autoionization is very thermodynamically unfavored near room temperature. I don't know much about water in a water-DMSO mixture, but let's take pure water as an example. The ...
- 6,418
4
votes
Are there any available tools to implement Jellium models?
The GPAW density functional theory code has a jellium mode (tutorials here). There is, e.g., a JelliumSlab class, where the charge neutralizing jellium background does not extend over all space, but ...
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10
votes
Textbooks for electronic structure theory
(We should add short descriptions to each of these as well as any new additions. Additionally, it would be good to break this list into categories, e.g. general, DFT, post-HF and many-body theories):
...
10
votes
Accepted
Analytic gradient and hessian for B3LYP
Yes, the expressions for the first and second order derivatives of most common functionals are known. However they include a term (the XC term) that requires numerical integration to calculate. So, ...
- 6,418
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