---
name: "gmx-sigeps"
section: "1"
platform: "linux"
package: "gromacs-data"
version: "2025.2-1"
release: "Debian 13 (Trixie)"
platforms: ["linux"]
url: "https://new.carta.tech/gmx-sigeps"
---

# gmx-sigeps(1)

Convert c6/12 or c6/cn combinations to and from sigma/epsilon

## NAME

gmx-sigeps - Convert c6/12 or c6/cn combinations to and from sigma/epsilon

## SYNOPSIS

```
gmx sigeps [-o [<.xvg>]] [-[no]w] [-xvg <enum>] [-c6 <real>]
           [-cn <real>] [-pow <int>] [-sig <real>] [-eps <real>]
           [-A <real>] [-B <real>] [-C <real>] [-qi <real>]
           [-qj <real>] [-sigfac <real>]
```

## DESCRIPTION

**gmx sigeps** is a simple utility that converts C6/C12 or C6/Cn combinations to sigma and epsilon, or vice versa. It can also plot the potential in  file. In addition, it makes an approximation of a Buckingham potential to a Lennard-Jones potential.

## OPTIONS

Options to specify output files:

- **-o \[\<.xvg\>\] (potje.xvg)**

  xvgr/xmgr file

Other options:

- **-\[no\]w (no)**

  View output *.xvg*, *.xpm*, *.eps* and *.pdb* files

- **-xvg \<enum\> (xmgrace)**

  xvg plot formatting: xmgrace, xmgr, none

- **-c6 \<real\> (0.001)**

  C6

- **-cn \<real\> (1e-06)**

  Constant for repulsion

- **-pow \<int\> (12)**

  Power of the repulsion term

- **-sig \<real\> (0.3)**

  sigma

- **-eps \<real\> (1)**

  epsilon

- **-A \<real\> (100000)**

  Buckingham A

- **-B \<real\> (32)**

  Buckingham B

- **-C \<real\> (0.001)**

  Buckingham C

- **-qi \<real\> (0)**

  qi

- **-qj \<real\> (0)**

  qj

- **-sigfac \<real\> (0.7)**

  Factor in front of sigma for starting the plot

## SEE ALSO

**[gmx(1)](/gmx/1.md)**

More information about GROMACS is available at \<*http://www.gromacs.org/*\>.

## COPYRIGHT

2025, GROMACS development team