[gmx-users] Index is larger than the number of atoms in the trajectory file

[Mahboobeh Eslami]

Hi all GMX usersI hope you are wellI have simulated a protein-ligand complex. My protein has two calcium ions. I want to use GMXPBSA approach for free energy calculation. 
If I remove calcium ions,  I will get following error in the first step of MMPBSA calculation:Fatal error:
Index[1673] 1676 is larger than the number of atoms in the
trajectory file (1675). There is a mismatch in the contents
of your -f, -s and/or -n files.How can I solve this problem. please guide me
Thank you so much