[lammps-users] heat capacity problem

Dear Lammps-users,
I have an interesting problem regarding running a particular type of simulation and I do not know how to go about it.

Bascially, I want to calculate heat capacity of my system. So, I want to add a certain amount of energy/time using fix heat command and want to keep track of temperature (as an independent parameter). Now, I can do this usnig fix nve (but this will keep the volume of the system constant). However, I want to keep the volume of the system to change according to its current temperature.

I tried using fix nph with fix heat and no temperature control ( I am not sure how correct it is?) but the simulation crashed after 5 timesteps in this case. (PPPM out of range error)…

With fix nve, the simulations are running fine…

Any ideas??

Thanks in advance.