# While trying to apply force field, i got this error **URL:** \ **Category:** User discussions\ **Created:** [December 21, 2024, 8:28am UTC](https://gromacs.bioexcel.eu/t/while-trying-to-apply-force-field-i-got-this-error/10875 "2024-12-21T08:28:31Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Deep](https://avatars.discourse-cdn.com/v4/letter/d/ce7236/32.png) [@Deep](https://gromacs.bioexcel.eu/u/Deep)\ **Post date:** [December 21, 2024, 8:28am UTC](https://gromacs.bioexcel.eu/t/while-trying-to-apply-force-field-i-got-this-error/10875/1 "2024-12-21T08:28:31Z")
Processing chain 1 ‘A’ (1364 atoms, 163 residues) Analysing hydrogen-bonding network for automated assignment of histidine protonation. 273 donors and 248 acceptors were found. There are 347 hydrogen bonds Will use HISD for residue 31 Identified residue MET1 as a starting terminus. Identified residue ASN163 as a ending terminus. 8 out of 8 lines of specbond.dat converted successfully Special Atom Distance matrix: MET1 MET6 HIS31 CYS54 CYS97 MET106 SD10 SD56 NE2276 SG446 SG808 SD883 MET6 SD56 0.631 HIS31 NE2276 2.196 1.931 CYS54 SG446 2.781 2.718 1.052 CYS97 SG808 0.820 0.539 2.117 2.897 MET106 SD883 1.900 1.314 1.848 2.841 1.635 MET120 SD982 2.525 2.014 3.286 4.293 2.112 1.520 Start terminus MET-1: MET1 End terminus ASN-163: COO- * * * Program: gmx pdb2gmx, version 2021.4-Ubuntu-2021.4-2 Source file: src/gromacs/gmxpreprocess/pdb2top.cpp (line 1104) Fatal error: atom C1 not found in buiding block 1MET while combining tdb and rtp For more information and tips for troubleshooting, please check the GROMACS website at [Common Errors — GROMACS webpage https://www.gromacs.org documentation](http://www.gromacs.org/Documentation/Errors) ---
**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:** [December 21, 2024, 12:03pm UTC](https://gromacs.bioexcel.eu/t/while-trying-to-apply-force-field-i-got-this-error/10875/2 "2024-12-21T12:03:19Z")
Posted yesterday (please Google or search the forum first): > [@Fatal error atom C2 not found in buiding block 166MET while combining tdb and rtp](https://gromacs.bioexcel.eu/t/fatal-error-atom-c2-not-found-in-buiding-block-166met-while-combining-tdb-and-rtp/10860/2): > > You need to interactively select terminal patching with the -ter option, otherwise an incorrect terminus is guessed (quirk of the CHARMM force field and a niche patch that is sometimes used). ---
**Author:** ![Deep](https://avatars.discourse-cdn.com/v4/letter/d/ce7236/32.png) [@Deep](https://gromacs.bioexcel.eu/u/Deep)\ **Post date:** [December 23, 2024, 9:06am UTC](https://gromacs.bioexcel.eu/t/while-trying-to-apply-force-field-i-got-this-error/10875/3 "2024-12-23T09:06:41Z")
Thank You sir