# How to Calculate the linear interaction energy **URL:** \ **Category:** User discussions\ **Tags:** mdp-parameters, free-energy\ **Created:** [January 6, 2022, 5:30pm UTC](https://gromacs.bioexcel.eu/t/how-to-calculate-the-linear-interaction-energy/3414 "2022-01-06T17:30:09Z")\ **Posts on this page:** 1\ **Showing post:** 14
**Author:** ![ebriand](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/ebriand/32/2314_2.png) [@ebriand](https://gromacs.bioexcel.eu/u/ebriand)\ **Post date:** [January 7, 2022, 8:16am UTC](https://gromacs.bioexcel.eu/t/how-to-calculate-the-linear-interaction-energy/3414/14 "2022-01-07T08:16:44Z")
There is a bug in `gmx lie` starting from gromacs 2018 or 2019. It will be fixed in 2022. You are affected by the bug if, in the ouput xvg file (`lie.xvg`), you see exactly the same value on each line. For instance: ```auto 0 48.5812 50 48.5812 100 48.5812 150 48.5812 200 48.5812 ``` (Though the value can be different for different system) If this is the case, the results obtained are incorrect. If it is necessary for you to perform LIE analysis at this time, you can use the [recently released 2022 beta 2](https://gromacs.bioexcel.eu/t/second-gromacs-2022-beta-release/3257). You do not need to perform the simulation again, just use the fixed `gmx lie` program contained in this version. --- _[View the full topic](https://gromacs.bioexcel.eu/t/how-to-calculate-the-linear-interaction-energy/3414)._