QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Sarvesh Agarwal on May 11, 2013, 09:29

Title: Electron Difference Density
Post by: Sarvesh Agarwal on May 11, 2013, 09:29

Sir please tell me, what this Electron Difference Density evaluates..?
if it finds the probability of the presence of electron, then with the attached C-O molecule there has to be blue surface near gold side (electronegativity--2.54) and red surface near carbon(electronegativity--2.55) but it is giving something Iam not able to understand... so please explain.. 

Title: Re: Electron Difference Density
Post by: kstokbro on May 13, 2013, 11:31

ElectronDifferenceDensity (EDD), returns the electron difference density, i.e. the difference between the self-consistent valence charge density and the superposition of atomic valence densities.

Thus, in a CO molecule there will be charge transfer from C to O, the EDD will be positive on O(more electrons) and negative on C (less electrons).

Title: Re: Electron Difference Density
Post by: Sarvesh Agarwal on May 28, 2013, 08:47

Thanks Sir...
    Is there any way to find the charge distribution from Electron Difference Density graph.

Title: Re: Electron Difference Density
Post by: Anders Blom on May 28, 2013, 09:20

Just calculate the ElectronDensity instead.

Title: Re: Electron Difference Density
Post by: Sarvesh Agarwal on June 6, 2013, 12:41

actually Iam using extended huckel because of time constraint.. and in that it does not calculate electron density
so is there any method or formula to find amount of charge, using EDD graph/data

Title: Re: Electron Difference Density
Post by: Anders Blom on June 7, 2013, 06:00

No. Computing this molecule with DFT takes about a minute so I don't see the time constraint being an issue...

Title: Re: Electron Difference Density
Post by: Sarvesh Agarwal on June 7, 2013, 07:10

THANKS..but I took this molecule just for example to clear my doubt, the structure which Iam simulating is metal CNT metal device with gas adsorption and it contains around 700 atoms..

Title: Re: Electron Difference Density
Post by: Anders Blom on June 7, 2013, 15:19

Ok :) There is not much to do, if you want to know the electron density you must use a method which can compute it. But most of the physics of the problem is contained in the difference density after all, it gives a fairly good idea of regions with electron/hole surplus.