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QuantumATK => General Questions and Answers => Topic started by: fso002 on March 3, 2015, 23:19

Title: Electron Density Difference with VNL
Post by: fso002 on March 3, 2015, 23:19

Good afternoon,

 I am using VNL to visualize results obtained with VASP calculations. I have the CONTCAR file and CHGCAR file but I want to know how do I get the electron density difference with VNL. Any help with this question is appreciated.

Thanks,
Fernando Soto

Title: Re: Electron Density Difference with VNL
Post by: Anders Blom on March 4, 2015, 09:31

I don't think that makes sense with VASP... The electron density (CHGCAR) would be the relevant thing.

Title: Re: Electron Density Difference with VNL
Post by: fso002 on March 4, 2015, 23:11

Good afternoon,

With the electron density difference plots one can visualize electron rich/depleted regions. It is a really helpful tool when doing charge transfer analysis.

Thanks,
Fernando A. Soto

Title: Re: Electron Density Difference with VNL
Post by: Anders Blom on March 4, 2015, 23:56

True, for sure. Tell it to the VASP developers ;)

Title: Re: Electron Density Difference with VNL
Post by: fso002 on March 5, 2015, 06:07

Good afternoon,

I found the following link:

https://www.youtube.com/watch?v=J4gsPMCyo4M

This is the "Virtual NanoLab - GUI for VASP #2 - Analyze VASP files" tutorial. Here, it is mentioned that I could obtain the charge density difference using the "grid operations" tool. Is this correct?

Thanks,
Fernando Soto

Title: Re: Electron Density Difference with VNL
Post by: Anders Blom on March 5, 2015, 09:35

That's for subtracting two densities from each other, in general. So in theory if you had the "neutral atom density" (NAD, the basic electron density of the individual atoms, superimposed in the given geometry), forming the difference of that to the self-consistent full electron density, you would obtain the difference density. But the question is, I suppose you don't have the NAD in VASP...

Title: Re: Electron Density Difference with VNL
Post by: Umberto Martinez on March 5, 2015, 14:03

Quote

This is the "Virtual NanoLab - GUI for VASP #2 - Analyze VASP files" tutorial. Here, it is mentioned that I could obtain the charge density difference using the "grid operations" tool. Is this correct?

Correct, provided that with charge density difference you mean:
- difference between spin up and spin down charge densities. From the LabFloor, slect your CHGCAR file from a spin-polarized calculation and click on Grid operations
- difference between the charge density of two or more systems (with and without an adsorbate, with and without a defect, an interface and the two componets, ...). From the LabFloor select the different CHGCAR files (by holding Ctrl) and click on Grid operation.

Please, also check Set up and analyze VASP calculations with Virtual NanoLab (http://quantumwise.com/publications/tutorials/item/523-set-up-and-analyze-vasp-calculations-with-vnl#grid_operations)