Hi guys.

I'm working on ionic liquids and I'm trying to visualize the surface charge density of some ions.

It seems that there is a problem in DMOL3 calculations for ions. I don't know why Materials Studio shows negative (red) surface in cations and positive (blue) surface in anions.

For comparison, I've shown 3 pictures for Pyridinium cation by 3 different software:

1-  ADF

2- COSMOtherm

3- Materials Studio

The first two pictures are created by ADF and COSMOtherm software, respectively.

Almost the same result is observed and they confirm the distribution of positive charge of the ion.

                                                                                  ADF                                                   COSMOtherm

But the last one which has been produced by Materials Studio, shows a strange negative charge distribution over the cation !

Here was my settings in DMOL3 module:

Task:                                   Geometry Optimization

Functional:                           B3LYP

DFT-D  correction method:     TS

Charge:                                 +1

Basis Set:                            TNP

Use Solvation Model:             checked

Other settings were default values.

I also tried different functional, basis sets, solvent, etc., but I got the same result.

Why does the Materials Studio produce different result for surface charge density ?

Same result have been observed for different cations ans anions.

e.g.:

bis((trifluoromethyl)sulfonyl)amide   anion

                              ADF                                                                           COSMOtherm        

                             Materials Studio