# Zero conformational entropy for each residue based on C-alpha atoms

**URL:** <https://gromacs.bioexcel.eu/t/zero-conformational-entropy-for-each-residue-based-on-c-alpha-atoms/4561>\
**Category:** User discussions\
**Created:** [August 5, 2022, 6:22am UTC](https://gromacs.bioexcel.eu/t/zero-conformational-entropy-for-each-residue-based-on-c-alpha-atoms/4561 "2022-08-05T06:22:48Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![qasimpars](https://avatars.discourse-cdn.com/v4/letter/q/977dab/32.png) [@qasimpars](https://gromacs.bioexcel.eu/u/qasimpars)\
**Post date:** [August 5, 2022, 6:22am UTC](https://gromacs.bioexcel.eu/t/zero-conformational-entropy-for-each-residue-based-on-c-alpha-atoms/4561/1 "2022-08-05T06:22:48Z")

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GROMACS version:2018.1

Dear users,

I am trying to calculate the conformational entropy per residue based on C-alpha atoms but I get zero value. I couldn’t figure out what the problem is.

First I generated an index file having a group for each residue. Then I used the below commands to calculate the entropy of each residue based on C-alpha atoms.

`echo 'C-alpha C-alpha_&_r_1' | gmx covar -s ref.pdb -f traj.pdb -n index.ndx`  
`gmx anaeig -v eigenvec.trr -entropy`

Unfortunately I get zero entropy for both `Quasiharmonic approach` and `Schlitter's formula` for all residues. Am I doing something wrong?

Thanks in advance