deviation in result

Dear Lammps users,
I used a CHARMM 22 force field optimized for my molecule which is ionic liquid. I checked the parameters three times, but the result that I get from my simulation has a great deviation from the article about 8% at the very exact situation of PVT. what could be possibly wrong? Also, there is some typo in the article, but using other force field and the structure, I tried to figure out what is the typo. How can I find the problem?
Best regards