Electron Difference Density

[Sarvesh Agarwal]

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.. 

[kstokbro]

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).

[Sarvesh Agarwal]

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

[Anders Blom]

Just calculate the ElectronDensity instead.

[Sarvesh Agarwal]

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

[Anders Blom]

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

[Sarvesh Agarwal]

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..

[Anders Blom]

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.