# How do I convert the parameters of Buckingham potential to the parameters of LJ

**URL:** <https://gromacs.bioexcel.eu/t/how-do-i-convert-the-parameters-of-buckingham-potential-to-the-parameters-of-lj/10687>\
**Category:** User discussions\
**Tags:** simulation-setup\
**Created:** [December 2, 2024, 12:52pm UTC](https://gromacs.bioexcel.eu/t/how-do-i-convert-the-parameters-of-buckingham-potential-to-the-parameters-of-lj/10687 "2024-12-02T12:52:13Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![qzzq](https://avatars.discourse-cdn.com/v4/letter/q/839c29/32.png) [@qzzq](https://gromacs.bioexcel.eu/u/qzzq)\
**Post date:** [December 2, 2024, 12:52pm UTC](https://gromacs.bioexcel.eu/t/how-do-i-convert-the-parameters-of-buckingham-potential-to-the-parameters-of-lj/10687/1 "2024-12-02T12:52:13Z")

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GROMACS version:2018.8  
GROMACS modification: No

Hello everyone,

I want to convert the parameters of Buckingham potential (A,B,C6) into the parameters of LJ potential (C6,C12). Is there any way to achieve this?

I noticed that one of the commands in gromacs was

> gmx sigeps

There’s a line in the manual about this command

> In addition, it makes an approximation of a Buckingham potential to a Lennard-Jones potential.

I tried this by substituting the Buckingham potential parameters (A,B,C6) from the literature

> gmx sigeps -A 200000 -B 34.07 -C 0.005 -o output.xvg

However, it also does not produce specific LJ potential C6,C12 values, but produces the following data:

 ![image](https://europe1.discourse-cdn.com/flex017/uploads/bioexcel1/original/2X/a/a7c0cea239c91c2c0688792ab18924e739d4f2e8.png)  
So I wonder if this command can get the LJ potential parameters (C6,C12) converted from the Buckingham potential parameters (A,B,C6)? If not, how can I get it?  
I’m feeling quite confused at the moment, and I would greatly appreciate it if someone could kindly help me. Thank you so much!