# What vdw and electrostatic parameters to use with Amber ff19sb

**URL:** <https://gromacs.bioexcel.eu/t/what-vdw-and-electrostatic-parameters-to-use-with-amber-ff19sb/8474>\
**Category:** User discussions\
**Created:** [February 29, 2024, 7:32pm UTC](https://gromacs.bioexcel.eu/t/what-vdw-and-electrostatic-parameters-to-use-with-amber-ff19sb/8474 "2024-02-29T19:32:28Z")\
**Posts on this page:** 3\
**Page:** 1

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**Author:** ![RomanS](https://avatars.discourse-cdn.com/v4/letter/r/5e9695/32.png) [@RomanS](https://gromacs.bioexcel.eu/u/RomanS)\
**Post date:** [February 29, 2024, 7:32pm UTC](https://gromacs.bioexcel.eu/t/what-vdw-and-electrostatic-parameters-to-use-with-amber-ff19sb/8474/1 "2024-02-29T19:32:28Z")

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GROMACS version: 2024  
GROMACS modification: No

I am planning to run simulations using ff19sb by preparing the system entirely using AmberTools, then converting the final topology and coordinate files to GROMACS format using ParmEd. However, in looking at the description of FFs in GROMACS, the [CHARMM section](https://manual.gromacs.org/current/user-guide/force-fields.html#charmm) says the following:

> For using CHARMM36 in GROMACS, please use the following settings in the mdp file:  
> constraints = h-bonds  
> cutoff-scheme = Verlet  
> vdwtype = cutoff  
> vdw-modifier = force-switch  
> rlist = 1.2  
> rvdw = 1.2  
> rvdw-switch = 1.0  
> coulombtype = PME  
> rcoulomb = 1.2  
> DispCorr = no

There is no comparable section for AMBER FFs, but the wording seems to imply that these values are to be used only with CHARMM36. What are the default values for these, and/or what values should be used with ff19sb?

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**Author:** ![Eduardneu](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/eduardneu/32/1976_2.png) [@Eduardneu](https://gromacs.bioexcel.eu/u/Eduardneu)\
**Post date:** [March 2, 2024, 1:51pm UTC](https://gromacs.bioexcel.eu/t/what-vdw-and-electrostatic-parameters-to-use-with-amber-ff19sb/8474/2 "2024-03-02T13:51:23Z")

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Hey,

you should not used the non-bonded interaction parameters specified for the CHARMM36 FF with the AMBER FF. There was a discussion about which parametes are needed for the AMBER FF [here](https://gromacs.bioexcel.eu/t/mdp-parameters-for-non-bonded-interaction-using-the-amber-force-field/6458/2).

Also you can not use ParmEd to convert a ff19sb topology to GROMACS format (see [here](https://gromacs.bioexcel.eu/t/how-to-properly-convert-the-cmaptypes-in-an-amber-topology-to-a-gromacs-topology/5866) and [here](https://github.com/ParmEd/ParmEd/issues/1292).

A possible alternative to generate a ff19sb topology in the GROMACS format would be [CHARMM-GUI](https://gromacs.bioexcel.eu/t/amber-ff19sb/3097) or using a [script](https://github.com/ParmEd/ParmEd/issues/1292) to convert the AMBER ff19sb topology to a GROMACS topology.

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**Author:** ![RomanS](https://avatars.discourse-cdn.com/v4/letter/r/5e9695/32.png) [@RomanS](https://gromacs.bioexcel.eu/u/RomanS)\
**Post date:** [March 4, 2024, 7:04pm UTC](https://gromacs.bioexcel.eu/t/what-vdw-and-electrostatic-parameters-to-use-with-amber-ff19sb/8474/3 "2024-03-04T19:04:26Z")

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Hi Eddie,

Thanks so much for your advice and all the references! I will try using the script in your last link to convert the topology.