Temperature fluctuations in NVT simulation with Nosé thermostat

[Subhasish Mallick]

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

[Que Zhu]

The structure might not be very stable.

Subhasish Mallick <subhasis...@mail.huji.ac.il> 于2025年8月19日周二 00:29写道：

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