[CP2K-user] [CP2K:21752] Temperature fluctuations in NVT simulation with Nosé thermostat

Subhasish Mallick subhasish.mallick at mail.huji.ac.il
Mon Aug 18 16:22:41 UTC 2025


Dear cp2k users,
I am running an NVT simulation for a biological system (~3500 atoms) at the 
BLYP-D3 level of theory using a Nosé–Hoover thermostat. The relevant 
section of my MD input is:
"
  &MD
    ENSEMBLE NVT
    STEPS 20000
    TIMESTEP 0.5
    TEMPERATURE 300.0
    COMVEL_TOL 1.0E-8
    &THERMOSTAT
      TYPE NOSE
      REGION MASSIVE
      &NOSE
      &END NOSE
    &END THERMOSTAT
  &END MD
"

During the simulation, I observed that the instantaneous temperature 
oscillates between ~280 K and ~330 K (see attached figure). Could someone 
please clarify whether this behavior indicates that the system has not yet 
reached equilibrium, or if it is primarily related to the thermostat 
settings?

Any guidance or suggestions would be greatly appreciated.

Thank you for your time and consideration.

Best regards,

Subho

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