thermal decomposition simulation using ReaxFF in GULP

Dear all,

I do a thermal decomposition simulation using ReaxFF in GULP, but it always remind me that error: volume has exceeded maximum allowed set by mdmaxvolume.

The parameters are: ensemble NPT, temperature 700K, thermostat parameter 0.1ps, pressure 0.0001GPa, barostat parameter 0.1ps, equilibration time 1ps, production time 30ps, time step 1fs. Would you please help me check out where is wrong?

Regards,

Wang