[gmx-developers] Regarding Calculation Charge

[David van der Spoel]

On 2014-12-08 12:56, MOHD HOMAIDUR RAHMAN wrote:
> Dear All
>
> I have four Ionic Liquid (IL) cation and anion. Each cation and anion
> make ILs pairs that have same cation with different anion and again same
> anion with different cation.
> Its means my combination is like that, for same cation
>
> Cation  +  Anion
>     A               B
>     A               C
>     A               D
>     A               E
>
> Again for same anion
>
> Cation  +  Anion
>     A                 B
>     A1               B
>     A2               B
>     A3               B
>
>  From this combination I have total sixteen pairs of cation and anion.
> In practice I am following this protocol for calculation of charge for
> these Ionic Liquid (ILs) pairs.
>
> Separately each pair of Ionic liquid are optimized and charge
> is calculating using gaussian one by one. Here I have confusion that can
> I used one cation charge with all different anion charge and in the same
> way one anion charge with different cation charge. This calculated
> charge I am using with OPLS force field.
>
> Please suggest me
> 1 Can I used the single calculated charge for cation with all different
> anion and vice-versa.
> 2 What are those important point I have to consider during the charge
> calculation.
>
> My choice of IL are ammonium, imadizolium based.
This is really a user question and not gromacs specific. Start by doing 
literature search. If you have done gaussian calculation you can run 
acpype (not part of gromacs) to get GAFF compatible force fields for use 
in gromacs.

>
> Thank you in advance for your guidance.
>
> Regards
> Rahman
>
> '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
> *Md Homaidur Rahman*
> PhD Research Scholar
> Computational Biophysics Lab.
> Department of Biotechnology
> Indian Institute of Technology-Madras
> Chennai-600 036
> *Mobile No = +91- 7845991785*
> '''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''''
>
>


-- 
David van der Spoel, Ph.D., Professor of Biology
Dept. of Cell & Molec. Biol., Uppsala University.
Box 596, 75124 Uppsala, Sweden. Phone:	+46184714205.
spoel at xray.bmc.uu.se    http://folding.bmc.uu.se