Dear ASE Community,
I am currently using the NPT method with a pressure setting of 0 to construct an NVT Nose-Hoover ensemble for my simulations, using MACE calculator. I have a few questions and would appreciate your insights.
My system is a super cell of NaZr₂(PO₄)₃ crystal under PBC condition, which is an orthorhombic crystal structure up to 400 K. To avoid NPT dynamic gets structure error, I am using Atom.set_cell command by removing so small off diagonal cell elements (10^-10A). I have tested the relaxation time constant (tau) and found it to work effectively around 20 fs, with a time step set to 1-2 fs.
My main concerns are:
- The temperature seems to converge around the desired value of 400 K, but I observe fluctuations of about ±20 K, typically around ±10 K, however, approximately every 70-100 fs, there is a sharp jump in temperature to 420 K or down to 380 K. Is this level of fluctuation considered high?
- The volume of the system remains completely fixed and shows no fluctuations at all. Is this expected behavior under the conditions I am using?
I appreciate any insights or advice you could provide regarding these observations.
Thank you for your assistance!