Otis,
I think the green surface is great and I was just wondering how it could be 
displayed for alkanes. My guess is that it's not displayed because when there 
is no partial charge, no MEP surface can be created. The problem is "how does 
Jmol guess there is no partial charge in the file?", and the answer seems to be 
"when all partial charges are set to 0.0". This rule appears to work generally 
except for alkanes, even if it can look silly to search for polarity on alkanes 
!
Paul

Le 11 mai 2012 à 18:13, Otis Rothenberger a écrit :

> Paul,
> 
> I need to clean that up on my page by trapping the zero partial charge on 
> alkanes. I don't know much about the calculation that Bob installed, but the 
> PUBCHEM_MMFF94_PARTIAL_CHARGES for alkanes are also zero. I was trapping 
> those files and making a slight adjustment to at least show the green surface 
> that suggests close to non-polar bonding. I broke this trap when I was adding 
> the dynamic MEP feature. Thanks for picking up on this.
> 
> Otis 
> 
> 
> --
> Otis Rothenberger
> [email protected]
> http://chemagic.com
> 
> 
> 
> 
> On May 11, 2012, at 10:47 AM, Pillot Paul wrote:
> 
>>> I've played with this new feature as well and I've found an unexpected 
>>> behavior : when the molecule is an alkane the VDW surface is not computed 
>>> and an error is issued, stating that the file does not contain partial 
>>> charges to display the MEP surface.
>>> 
>>> The calculate partialcharge command runs just fine. Of course there are no 
>>> partial charges for these alkane models so that is certainly the cause for 
>>> the error.
>>> 
>>> 
>>> 
>>> Nonetheless, in modelkit, if I create first a model with partial charges 
>>> and a MEP surface, and I subsequently remove from that model atoms or 
>>> reduce bonds order to get an alkane, then a green MEP surface is displayed.
>>> 
>>> 
>>> 
>>> In Otis' page, this problem doesn't appear when one chooses to start from 
>>> C2H6 (green MEP surface is displayed). I suspect that's because the 
>>> ethene.txt file used there has charges set (-0.0680 for C and 0.0227 for H) 
>>>  ... In Bob's "simple" page, this can be tested by loading ethan from NCI 
>>> and try to display MEP (no surface displayed).
>>> 
>>> Paul
>>> 
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