# Error in GB implicit solvent .tpr file generation **URL:** \ **Category:** User discussions\ **Tags:** forcefield, mdrun\ **Created:** [May 9, 2023, 12:09am UTC](https://gromacs.bioexcel.eu/t/error-in-gb-implicit-solvent-tpr-file-generation/6355 "2023-05-09T00:09:30Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![roozi](https://avatars.discourse-cdn.com/v4/letter/r/958977/32.png) [@roozi](https://gromacs.bioexcel.eu/u/roozi)\ **Post date:** [May 9, 2023, 12:09am UTC](https://gromacs.bioexcel.eu/t/error-in-gb-implicit-solvent-tpr-file-generation/6355/1 "2023-05-09T00:09:30Z")
GROMACS version:2018.8 GROMACS modification: No Hi there, I got an error message when running grompp for gb implicit solvent model : Fatal error: Can’t do GB electrostatics; the implicit\_genborn\_params section of the forcefield is missing parameters for 31 atomtypes or they might be negative. i have used Charmm36m FF for topology files generation . I also tried older Charmm36 FF hoping to resolve the error but i got the same error again. The molecules are Glycoproteins. It will be very helpful if some one can guide me to a solution. ---
**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:** [May 9, 2023, 5:09pm UTC](https://gromacs.bioexcel.eu/t/error-in-gb-implicit-solvent-tpr-file-generation/6355/2 "2023-05-09T17:09:45Z")
CHARMM36 does not support GB models in GROMACS. I thought that code was removed years ago, anyway. ---
**Author:** ![roozi](https://avatars.discourse-cdn.com/v4/letter/r/958977/32.png) [@roozi](https://gromacs.bioexcel.eu/u/roozi)\ **Post date:** [May 9, 2023, 5:33pm UTC](https://gromacs.bioexcel.eu/t/error-in-gb-implicit-solvent-tpr-file-generation/6355/3 "2023-05-09T17:33:55Z")
thanks. the functionality is deprecated in 2019 version. which FF may i use to implement GB implicit solvent topology generation?