Questions tagged [conceptual-dft]

Questions about conceptual DFT.

Filter by
Sorted by
Tagged with
4 votes
1 answer

Can the Electron Charge Density (ECD) have negative values and why?

In certain charge densities I am getting negative values, in the place where the atomic cores would be. I do not have access to the vasp.xml or OUTCAR files, so there is no way to determine whether ...
4 votes
0 answers

DFT+U: localizing electrons on combination of atomic orbitals

TLDR: DFT+U is a cheap scheme to help localize electrons on atomic orbitals by penalizing fractional occupancies of such orbitals. However, when one tries to localize an electron/hole on an atomic ...
45 votes
10 answers

What are the types of charge analysis?

I am evaluating the atomic charge of a system using inter-atomic potentials and comparing with using DFT. I know about the following types of partial charge: Mulliken, Bader, Qeq. I wonder what are ...
4 votes
1 answer

What does the "atomic pseudo charge-density" in the POTCAR file stand for?

Basically I am trying to find the initial guess of an atomic charge density [rho(r)] v/s the radial distance r. Specifically I checked the "atomic pseudo charge-density" tag in the POTCAR ...
1 vote
1 answer

Interstitial charge from a cube file: Need help in python coding

I have a test material- two silicon atoms in an unit cell. This particular structure shows evidence of having interstitial charge between the two atoms. I need to find out the amount of this ...
4 votes
1 answer

Does integrating PDOS give total charge of a system?

Suppose you have a two atom cubic cell, and you have calculated the atomic PDOS. Does integrating the atomic PDOS and summing them to Fermi energy give exactly the total charge of a system?
6 votes
2 answers

How to calculate the individual atomic charge from a cube file of charge density?

I have a cube file of charge density. The unit cell consists two silicon atoms. If I use a python code to calculate the net charge of the system, it results around 24, which is ok because the ...
2 votes
1 answer

What is the basic equation for total charge calculation from a 3D cube file of charge density file?

I have a 3D charge density file, calculated from Quantum Espresso DFT. If someone calculates the total charge (number of electrons) of an unit cell from that cube file (using a numerical approximation ...
4 votes
1 answer

Is there any free software that helps to know specific charge densities or ELFs at any position of the material?

Can anyone suggest some free software that can visualize the charge density and/or electron localization function (ELF)? More importantly, can we determine/know those values (charge density and/or ELF)...
6 votes
1 answer

Total number of electrons from DOS and PDOS - what's the theory behind it?

Let say we need to determine the total number of electrons of an FCC material (let say, two silicon atoms in the unit cell, using numerical/mathematical approach. How can we get the total number of ...
4 votes
1 answer

Elastic Calculation and dipole tensor calculation using VASP

I am a beginner in learning DFT calculation with VASP. I have just done a relaxation calculation. I want to learn calculating two properties of materials, using VASP. One is the elastic properties (...
14 votes
3 answers

Bond Order: When and how is it used today?

We all learned about single vs double vs triple bonds in high school chemistry and biology. We learned that unsaturated fats have double bonds whereas saturated fats have only single bonds, which ...
11 votes
0 answers

Should augmented basis be used for Hirshfeld charges? [closed]

I'm calculating condensed Fukui functions to explain the reactivity of my molecules. The manual for Multiwfn suggests using atomic dipole moment corrected Hirshfeld charges for it. However I get ...
7 votes
2 answers

How to take periodic snapshots while running a simulation in VASP?

Same question, rephrased: What is the procedure to take snapshots at fixed intervals while running an AIMD or DFT Simulation in VASP? OR Which parameter in the INCAR file do I modify to achieve ...
17 votes
1 answer

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 ...
21 votes
4 answers

What are the types of bond orders?

I am studying the interaction of a metal with a nanostructure. As we can not trust graphical software about the bond formation, I decided to analyze them using the software Multiwfn. It happens that ...
7 votes
1 answer

Are there properties that can only be calculated with a given set-up?

If you do a bibliography search about the codes used in matter modeling, you will find a large list. I played with a few of them (both free and commercial) and one of my findings is that the ...