Charge vs. van der walls electrostatic potential

If I view the "surface" > electrostatic potential > van der walls in MarvinSpace, sometimes I get and all red surface, for example, but, when I look at the charge in MarvinSketch for the same molecule, the cloud is red and blue. This is important to me in seeing if a molecule has a permanent dipole moment. Which one is more true? Thanks.

Hi Joe,





can you give us a sample structure to reproduce this in case the data is not confidential?





Kind regards,


Judit

here's an example of a generic molecule to illustrate the point





N+(C2H5)4

For the first look it seems that something is wrong with the electrostatic potential coloring in MSpace, but it requires more time to find out the reason precisely.


The ChargePlugin display result used through MarvinSketch is reliable.

the example molecule is pretty much symmetric, and therefore should not have a permanent dipole in it. Therefore, perhaps the Mspace blue charge cloud is showing the result of the red/blue Msketch parts canceling each other out?

Hi Joe,





actually, both MSketch and MSpace coloured surfaces are correct, but they map somewhat different values on the same surface and this is what causes some confusion.





In both cases the partial atom charges calculated and places in the centre of the atoms. The surface in MSketch estimates the electrostatic potential on the surface points, while MSpace uses a formula similar to the Coulomb's law (or electric field).


I'm not sure which is more relevant. If you can advise us a simple model that is adequate for your (and thus supposedly for others') needs then we can implement it quickly.





Does this make sense?





Regards,


Miklos

Hi Joe,





any wise thoughts from you regarding this issue?





Thanks


Miklos