Hello,
I am trying to run an NPT simulation where the temperature is controlled using the Andersen thermostat algorithm and the pressure is controlled using the Parrinello barostat algorithm on a nylon66 crystal structure provided by materials studio (Structures\polymers\crystalline\nylon-6-6-alpha.xsd).
When I import the file I first hydrate it since it appears to be missing some hydrogens. After that I make a supercell and apply the COMPASS force field to the crystal prior to submitting it to discover on the supercomputer.
The relevant portion of the script is below:
dynamics \
time = 100000.00 \
boltzmann \
timestep = 1.00 \
initial_temperature = 300.00 \
ensemble = NPT \
temperature_control_method = andersen \
collision_ratio = 1.00 \
temperature = 300.00 \
press_choice = stress \
stress = {0.00000 0.00000 0.00000 0.00000 0.00000 0.00000 } \
pressure_control_method = parrinello \
cell_mass = 20.0 \
deviation = 50000.00 \
I get the error "Error: Dynamics: Energy difference between successive steps in dynamics is greater than the user defined variable DEVIATION, 50000.00"
I looked at decreasing the timestep of 0.10 and increased deviation to 100000000.00, and I get the same error.
When I looked at a different supercell, I could get it to run but the volume gets really big, such that the density is pretty much zero. Not sure what is wrong. I did this for other crystal structures and did not have this problem.
Thanks,
Tanya