# Fatal eror adding entry in rtp

**URL:** https://gromacs.bioexcel.eu/t/fatal-eror-adding-entry-in-rtp/9289
**Category:** User discussions
**Created:** [June 3, 2024, 4:51pm UTC](https://gromacs.bioexcel.eu/t/fatal-eror-adding-entry-in-rtp/9289 "2024-06-03T16:51:12Z")
**Posts on this page:** 2
**Page:** 1

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### Author: ![alexmathew](https://avatars.discourse-cdn.com/v4/letter/a/f4b2a3/32.png) [@alexmathew](https://gromacs.bioexcel.eu/u/alexmathew)
#### Post date: [June 3, 2024, 4:51pm UTC](https://gromacs.bioexcel.eu/t/fatal-eror-adding-entry-in-rtp/9289/1 "2024-06-03T16:51:12Z")

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Hello everyone,  
Im trying to add NH3 terminal in the amber forcefield by modifying the rtp entry as below

```auto
 [NH3]
 [atoms]
     N N -0.267522 ; charge from RESP
    H1 H 0.422507 ; charge from RESP
    H2 H 0.422507 ; charge from RESP
    H3 H 0.422507 ; charge from RESP
 [bonds]
     N H1
     N H2
     N H3
    -C N ; bond to the previous C-terminus
 [impropers]
     N H1 H2 H3

```

when i invoke pdb2gmx i get the following error

```auto
Reading residue database... (Amber99sb-ildn)
Opening force field file ./amber99sb-ildn.ff/aminoacids.rtp

-------------------------------------------------------
Program: gmx pdb2gmx, version 2023.3
Source file: src/gromacs/gmxpreprocess/resall.cpp (line 465)

Fatal error:
in .rtp file in residue NH3 at line:
     N N -0.267522

```

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<div class="post-metadata">

### Author: ![Seyilaxa](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/seyilaxa/32/3136_2.png) [@Seyilaxa](https://gromacs.bioexcel.eu/u/Seyilaxa)
#### Post date: [June 3, 2024, 5:34pm UTC](https://gromacs.bioexcel.eu/t/fatal-eror-adding-entry-in-rtp/9289/2 "2024-06-03T17:34:10Z")

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I think it’s because the last column of atom numbers in [atoms] are missing.