# How to obtain the polarizable water model，such as: tip4p-FQ or SWM4-NDP **URL:** \ **Category:** User discussions\ **Created:** [June 15, 2020, 2:17am UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-polarizable-water-model-such-as-tip4p-fq-or-swm4-ndp/314 "2020-06-15T02:17:01Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Silentium](https://avatars.discourse-cdn.com/v4/letter/s/f9ae1b/32.png) [@Silentium](https://gromacs.bioexcel.eu/u/Silentium)\ **Post date:** [June 15, 2020, 2:17am UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-polarizable-water-model-such-as-tip4p-fq-or-swm4-ndp/314/1 "2020-06-15T02:17:01Z")
GROMACS version: GROMACS modification: Yes/No Here post your question: Hi, all I am trying to select the polarizable water model for my simulation. Where to get the tip4p-fq.itp? By the way, swm4-ndp.itp found in [http://mackerell.umaryland.edu/charmm\_drude\_ff.shtml](http://mackerell.umaryland.edu/charmm_drude_ff.shtml), but the gmx genion seemed could not add ions correctly. Many thanks ---
**Author:** ![Er1ck](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/er1ck/32/132_2.png) [@Er1ck](https://gromacs.bioexcel.eu/u/Er1ck)\ **Post date:** [June 15, 2020, 2:40am UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-polarizable-water-model-such-as-tip4p-fq-or-swm4-ndp/314/2 "2020-06-15T02:40:01Z")
I may be wrong since I haven’t use polarizable water model. I think one way is to use the TIP4P model since both are 4 site water models. I am afraid you may need to manually update the force field of water model in the topology file if your gromacs doesn’t have the corresponding water potentials. Lastly, run a quick energy minimization, which should eliminate the differences in the water structures. ---
**Author:** ![jalemkul](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/jalemkul/32/18_2.png) [@jalemkul](https://gromacs.bioexcel.eu/u/jalemkul)\ **Post date:** [June 15, 2020, 5:31pm UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-polarizable-water-model-such-as-tip4p-fq-or-swm4-ndp/314/3 "2020-06-15T17:31:18Z")
> [@Silentium](#): > > By the way, swm4-ndp.itp found in [MacKerell Lab](http://mackerell.umaryland.edu/charmm_drude_ff.shtml), but the gmx genion seemed could not add ions correctly. It does if you check out the Drude branch of the GROMACS git repository, but it’s still being worked on. `gmx genion` will work and will add polarizable ions to the system automatically. ---
**Author:** ![Silentium](https://avatars.discourse-cdn.com/v4/letter/s/f9ae1b/32.png) [@Silentium](https://gromacs.bioexcel.eu/u/Silentium)\ **Post date:** [June 16, 2020, 1:39am UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-polarizable-water-model-such-as-tip4p-fq-or-swm4-ndp/314/4 "2020-06-16T01:39:08Z")
gmx genion could only add one atom ions，but ions has two atom in ions.itp of Drude. If I manually add the second atom of ions, after gmx grompp, gmx could not find the default bond type ![IMG_20200616_093348](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/1X/8413d2f8185f7f5339fb0ce4554faaf232b64123.jpeg) ---
**Author:** ![Silentium](https://avatars.discourse-cdn.com/v4/letter/s/f9ae1b/32.png) [@Silentium](https://gromacs.bioexcel.eu/u/Silentium)\ **Post date:** [June 16, 2020, 1:44am UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-polarizable-water-model-such-as-tip4p-fq-or-swm4-ndp/314/5 "2020-06-16T01:44:41Z")
> [@Er1ck](#): > > I am afraid you may need to manually update the force field of water model in the topology file if your gromacs doesn’t have the corresponding water potentials I’m not sure what do you mean, I need change the parameters in tip4p.itp? ---
**Author:** ![Er1ck](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/er1ck/32/132_2.png) [@Er1ck](https://gromacs.bioexcel.eu/u/Er1ck)\ **Post date:** [June 16, 2020, 2:17am UTC](https://gromacs.bioexcel.eu/t/how-to-obtain-the-polarizable-water-model-such-as-tip4p-fq-or-swm4-ndp/314/6 "2020-06-16T02:17:33Z")
gmx genion can update the toplogy file \ ***.top** if you selected this option. I don’t think GROMACS includes tip4p-fq potential by default. Therefore, you need to edit \*.top the one that will be compiled into the \ ***.tpr** file for mdrun. The error messages indicates some inconsistency in your \ ***.top** file (and the associated itp files). It seems that new atom types are introduced but the corresponding bonds are not properly defined.