If I understand, you are using your own pair style, which competes
the viral which contributes to the pressure. If the pressure is “wrong”
it could be due to your pair style. Do you have the same problem
if you use only pair styles provided with LAMMPS?
Steve
You also need to insure that the temp/pressure you are comparing to, account the
the rigid-body degrees-of-freedom which affect both the temperature
and kinetic portion of the pressure. I.e. that what NPT is using for its
pressure and temperature is the same as what you are printing with the thermo output.
Steve