I am a user of the VASP code. I relax the atomic positions of a supercell containing an impurity atom. For relaxation, I set
ISYM = 0
Then, I try to perform a static calculation. For this step, I set
ISYM = 2
However, I got an error along with suggestion:
VERY BAD NEWS! internal error in subroutine INVGRP:
inverse of rotation matrix was not found (increase SYMPREC) 2
Following the suggestion, I increase SYMPREC (from the default value $10^{-5}$) to $10^{-4}$, and the error happened again. Instead, when I decrease SYMPREC to $10^{-6}$, the error is gone.
I am confused that what does "increase SYMPREC" mean in the above suggestion. Could someone help explain? What are the side effects when tuning the SYMPREC?