[CP2K-user] [CP2K:21206] Inquiry Regarding Temperature Stability in Langevin MD Simulation with Graphene and Fe Atom System

[张逸晨]

Dear CP2K Community,

I am reaching out to seek advice on a temperature stability issue I am 
facing during a Langevin molecular dynamics simulation.

My simulation setup involves a single Fe atom loaded on a graphene sheet, 
with an additional 20 Å water (mass of H has been set to 2) layer added to 
the system. Despite using the following parameters for my simulation:

&MD
   TIMESTEP 1
   TEMPERATURE 298.15
   ENSEMBLE LANGEVIN
   STEPS 1000
      &LANGEVIN
        GAMMA 0.01
        NOISY_GAMMA 0.0001
      &END LANGEVIN
      &THERMAL_REGION
       DO_LANGEVIN_DEFAULT F
       &DEFINE_REGION
         TEMPERATURE 298.15
         DO_LANGEVIN T
         LIST 1..282 377..517
         NOISY_GAMMA_REGION 2.2E-4
       &END DEFINE_REGION
       &DEFINE_REGION
         TEMPERATURE 298.15
         DO_LANGEVIN T
         LIST 283..376 518
         NOISY_GAMMA_REGION 5E-5
       &END DEFINE_REGION
      &END THERMAL_REGION
  &END MD

I am noticing that the temperature in the ener file is continuously 
dropping, despite the target temperature being set at 298.15 K. I am 
wondering if there is something wrong with my settings or if there is a 
particular aspect I should adjust to keep the temperature stable around 300 
K, especially considering the inclusion of both the graphene sheet and the 
water layer.

Has anyone encountered a similar issue or have any suggestions on how to 
achieve better temperature stability in Langevin dynamics with these 
parameters?

I would greatly appreciate any insights or advice on this matter.

Best regards,
Zhang Yichen

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