[ghemical-devel] 1,4-scaling in ghemical tripos-5.2 forcefield

[Tim Vandermeersch]

Hello,

> and sorry for the late answer.

No problem, I don't always answer that fast myself as you can see :)

>I have not had time to look at the problem
> yet, I only briefly looked at tripos-5.2 original paper. I tried to find
> there what the 1,4 scaling factor should be, but I didn't find it so far.
>
> Do you know what the scaling factor should be in tripos-5.2?

No, but it is not the value of the scaling factor that I need (In
ghemical it's 0.5). Attached are three files:

benzene.gpr: coordinate file for benzene in gpr format

ghemical_benzene.log: output (individual interactions) for libghemical

(this is done with a modified version of the libghemical SVN
example2.cpp and some editing to mimic openbabel's output style. I
could send you this patch if you would be interested

openbabel_benzene.log: same for openbabel

Comparing the log files:
- for VDW interaction 1, 5 and 9:   0.5 * E_ghemical = E_openbabel
- these interactions are the 1,4 interactions for the carbon atoms in the ring
- openbabel scales them, libghemical does not.

Is this a bug, or should these interactions not be scaled?

Thanks in advance,
Tim
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