# How to find Isothermal Compressibility for Acetone **URL:** \ **Category:** User discussions\ **Created:** [March 30, 2024, 9:20am UTC](https://gromacs.bioexcel.eu/t/how-to-find-isothermal-compressibility-for-acetone/8737 "2024-03-30T09:20:16Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Lukhmanul](https://avatars.discourse-cdn.com/v4/letter/l/f17d59/32.png) [@Lukhmanul](https://gromacs.bioexcel.eu/u/Lukhmanul)\ **Post date:** [March 30, 2024, 9:20am UTC](https://gromacs.bioexcel.eu/t/how-to-find-isothermal-compressibility-for-acetone/8737/1 "2024-03-30T09:20:16Z")
Dear Sir, I’ve noticed that the 'gmx energy -f nvt.edr -s nvt.tpr -nmol 786 -fluct\_props ’ command does not offer an option to select volume to calculate the isothermal compressibility. Could you kindly advise on the appropriate approach or alternative command to achieve this calculation?. Looking forward to your guidance. Best regards, LUKHMANUL HAKEEM K. ---
**Author:** ![MichelePellegrino](https://dub1.discourse-cdn.com/flex017/user_avatar/gromacs.bioexcel.eu/michelepellegrino/32/628_2.png) [@MichelePellegrino](https://gromacs.bioexcel.eu/u/MichelePellegrino)\ **Post date:** [March 30, 2024, 12:39pm UTC](https://gromacs.bioexcel.eu/t/how-to-find-isothermal-compressibility-for-acetone/8737/2 "2024-03-30T12:39:16Z")
Hi Lukhmanul, If it’s a NVT run (which I guess from the name of the input and output files), the volume is not returned by `gmx energy` simply because it’s fixed. I think you have to run at constant pressure instead. ---
**Author:** ![Lukhmanul](https://avatars.discourse-cdn.com/v4/letter/l/f17d59/32.png) [@Lukhmanul](https://gromacs.bioexcel.eu/u/Lukhmanul)\ **Post date:** [March 30, 2024, 1:41pm UTC](https://gromacs.bioexcel.eu/t/how-to-find-isothermal-compressibility-for-acetone/8737/3 "2024-03-30T13:41:13Z")
Ok, Thank you sir.