40
votes
Accepted
What is the closest thing we have to "the" universal density functional?
I think this question somewhat comes down to what "camp" of DFT progression you subscribe to. I should specify upfront that this summary is mainly centered around molecular systems, so some of the ...
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40
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Is there a database where we can find previously determined geometries of materials?
I agree with the other answer but there are many other resources:
Open Crystallographic Database which includes a large set of experimental crystal structures.
There's a related Theoretical ...
- 9,045
39
votes
Is there a database where we can find previously determined geometries of materials?
There is the Materials Project:
https://materialsproject.org/
From the site:
Harnessing the power of supercomputing and state of the art electronic structure methods, the Materials Project provides ...
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38
votes
Accepted
Was Walter Kohn wrong about this?
Kohn is easily one of my favorite humans of all time, and he was a role model to whom I looked up in great admiration for most of my academic life; in fact before this site was created, I proposed ...
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31
votes
Accepted
Is there a database where we can find previously determined geometries of materials?
2DMatPedia
An open computational database of two-dimensional materials. A large dataset of 2D materials, with more than 6,000 monolayer structures, obtained from both top-down and bottom-up ...
- 8,922
26
votes
What is the largest material that has been studied using density functional theory?
Here is a DFT simulation of a virus, in solution!
"Combining Linear-Scaling DFT with Subsystem DFT in
Born-Oppenheimer and Ehrenfest Molecular Dynamics
simulations: from Molecules to a Virus in ...
- 33.6k
26
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Is there a database where we can find previously determined geometries of materials?
Depending on what kind of materials looking for the following crystallographic databases can be relevant, too (unfortunately, for a cost):
Inorganic Crystal Structure Database (ICSD) by Karlsruhe ...
- 1,807
24
votes
Is there a database where we can find previously determined geometries of materials?
In addition to above recommendations, I also use American Mineralogist Crystal Structure Database.
http://rruff.geo.arizona.edu/AMS/amcsd.php
The good thing about this place is that you can check ...
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22
votes
Accepted
What is the largest material that has been studied using density functional theory?
I know of several papers over the million-atom mark:
2,097,152 atoms "Calculations for millions of atoms with density functional theory: linear scaling shows its potential"
1,012,500 atoms using ...
- 9,045
19
votes
Accepted
When do we abandon ab initio methods?
There's three scenarios that come to my mind, for when ab initio methods get abandoned:
The cost becomes prohibitive (e.g. too many electrons)
The insight is lost
It is simply not required for what ...
- 33.6k
18
votes
Is there a database where we can find previously determined geometries of materials?
Awesome Materials Informatics
The community-edited awesome materials informatics list has a section on "machine-readable datasets", many of which contain atomic structures of materials.
- 2,534
17
votes
What are the positives and negatives of periodic DFT codes that don't use plane-wave basis sets?
The main positives:
you can do all-electron calculations
you don't need to set up pseudopotentials / PAWs
you can study core properties
you can use hybrid functionals cheaper / run post-HF ...
- 18k
17
votes
What is the closest thing we have to "the" universal density functional?
I'm not entirely sure what you mean by "universal".
If you mean a functional that can model a wide variety of materials with reasonable success, probably the closest we have are GGA functionals. ...
- 348
17
votes
Accepted
How to calculate energy of a molecule in an aligned electric field?
Aligning a molecule to a particular frame of reference (e.g., with the z-axis along a particular bond) is part of Avogadro for this reason:
In Avogadro 1.x, there's an align tool
You click one atom ...
- 9,045
16
votes
What is the closest thing we have to "the" universal density functional?
This paper published by Bikash Kanungo, Paul M. Zimmerman & Vikram Gavini provide an interesting solution to getting closer to a "universal functional"
Exact exchange-correlation potentials from ...
- 7,957
16
votes
How to understand the spin of exciton?
As you mentioned in the question, excitons are indeed bound electron-hole pairs. They are often considered to be the signature of optical spectra in insulating solids. Adding onto the comment by tmph, ...
- 2,332
16
votes
Solving the Schrödinger equation as a service?
SciCalQ
The company does more than solving the Schroedinger equation. From its site:
SciCalQ’s solid background in computational chemistry and quantum physics own extensive experiences in solving ...
- 22.3k
15
votes
Accepted
How to overcome the exponential wall encountered in full configurational interaction methods?
It is hard to claim that any FCI code overcomes the exponential wall, especially for strongly correlated systems.
There are many algorithms, e.g. CDFCI, HCI, FCIQMC, ACI, etc., which significantly ...
- 1,076
15
votes
Accepted
What are the positives and negatives of periodic DFT codes that don't use plane-wave basis sets?
Pure plane-wave basis sets have the following advantages when used in periodic DFT (or HF) simulations:
Orthogonal
Computationally simple (operators with derivatives are particularly straightforward)
...
- 6,567
14
votes
Accepted
What methods can be used to calculate excited-states in molecular crystals?
There's two facets to this question:
What methods can be used for excited states in crystals? (the title, and final sentence)
What methods can be used for excited states with plane waves? (paragraphs ...
- 33.6k
14
votes
What are the positives and negatives of periodic DFT codes that don't use plane-wave basis sets?
One important property of atom-centered basis sets is that electrons can only be localized on atoms. This is a problematic property when modeling solid systems with defects.
For instance, at a color ...
- 323
14
votes
How do I simulate the interaction between two atoms?
EDIT Doing what you want is hard! You will need a full quantum mechanics based simulation. This is unlikely to be something you can build yourself at the current time.
Based on your new additions to ...
- 319
13
votes
Solving the Schrödinger equation as a service?
Protheragen
Protheragen offers a Quantum Chemistry Service which includes:
ECD calculation service (absolute configuration determination)
Quantitative calculations (quantum chemical calculations)
QM, ...
- 33.6k
13
votes
How do I simulate the interaction between two atoms?
How to proceed depends on how accurate you want the outcome. Throughout my answer I will provide blue buttons which demonstrate that there's entire tags in our community to address certain aspects of ...
- 33.6k
13
votes
Do bonds between the atoms influence ab-initio energies?
The bonds you draw or see in Gaussview should have no effect on the calculation (besides some minor effects in choosing internal coordinates for a geometry optimization). As you note, a bond is a ...
- 15.2k
12
votes
What is the closest thing we have to "the" universal density functional?
Since this is a very active research topic the answer here might change regularly. Just within the last few months we've seen updates to the SCAN functional in the form of r2SCAN and the de-...
- 1,491
12
votes
Can ab initio crystal structure methods predict the structure of cuprates from their stoichiometry and quantify the brittleness of those materials?
Check the USPEX method which is mainly a crystal structure prediction code. It uses the evolutionary algorithm to find the global minimum on the potential energy surface of a material, thereby ...
- 5,125
12
votes
Accepted
DFT Knowledge Check for Posed Problem
I agree with Camps that your best bet is to look at a potential advisor and see what they study. Your given example might be a bit of a stretch for some computational materials science advisors, due ...
- 10.8k
12
votes
Accepted
How to make sure that my SCF calculation is correct?
First, make sure that the structure is correct.
Second, make sure that the structure is relaxed.
Third, make sure that all the parameters in your input card are reasonable and the used ...
- 14.9k
12
votes
How may I calculate the bond length between two atoms?
The only proper way to do it ab initio is to calculate the energy (E) for various internuclear distances (R) and then to approximate the equilibrium bond length by choosing the distance which has the ...
- 33.6k
Only top scored, non community-wiki answers of a minimum length are eligible