# \[SOLVED\] Source of ion parameters in the Amber port

**URL:** <https://gromacs.bioexcel.eu/t/solved-source-of-ion-parameters-in-the-amber-port/2615>\
**Category:** User discussions\
**Created:** [July 29, 2021, 9:39pm UTC](https://gromacs.bioexcel.eu/t/solved-source-of-ion-parameters-in-the-amber-port/2615 "2021-07-29T21:39:07Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![bkav](https://avatars.discourse-cdn.com/v4/letter/b/f17d59/32.png) [@bkav](https://gromacs.bioexcel.eu/u/bkav)\
**Post date:** [July 29, 2021, 9:39pm UTC](https://gromacs.bioexcel.eu/t/solved-source-of-ion-parameters-in-the-amber-port/2615/1 "2021-07-29T21:39:07Z")

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GROMACS version:  
GROMACS modification: No

Dear All,

In the Amber force field port for the Gromacs, I find only one single epsilon/sigma parameters for the mono- and divalent ions/cations. I tried to track the origin of these parameters without any luck; they look neither like Joung-Cheatham nor the Aqvist ion parameters. Does anyone know anything about this?

Thank you all!

Edit: I have found the answer. Apparently these ion parameters are included in the parm99 files of Amber package and 1990 Amber-adapted Aqvist parameters. I leave this here in case someone comes up with the same question in the future. Sorry for the false alarm.

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**Author:** ![xzeng](https://avatars.discourse-cdn.com/v4/letter/x/7993a0/32.png) [@xzeng](https://gromacs.bioexcel.eu/u/xzeng)\
**Post date:** [May 6, 2022, 11:33pm UTC](https://gromacs.bioexcel.eu/t/solved-source-of-ion-parameters-in-the-amber-port/2615/2 "2022-05-06T23:33:27Z")

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Thanks @bkav for this, I was just looking for the reference for the ion parameters.