[CP2K-user] [CP2K:14555] AIMD simulation of a single water molecule

[Krack Matthias (PSI)]

Hi

A single water molecule has only a few degrees of freedoms which results in large temperature fluctuations when potential energy is transferred to kinetic energy. Try a larger water sample, e.g. 32 molecules, since these fluctuations should average out more and more for larger systems.

Matthias

Von: cp... at googlegroups.com <cp... at googlegroups.com> Im Auftrag von Junbo Lu
Gesendet: Freitag, 15. Januar 2021 13:03
An: cp2k <cp... at googlegroups.com>
Betreff: [CP2K:14555] AIMD simulation of a single water molecule

Hi,
    I am trying to use CP2K to run NVT simulation for a single water molecule. But I find that the temperature fluctuates seriously. I can not get equilibrium temperature. I set the temprature as 300 K in the input file. But the temperatures in energy file are:
......
      3070         1535.000000         0.002485140       523.162866214
      3071         1535.500000         0.002714404       571.426577303
      3072         1536.000000         0.003027088       637.251846392
      3073         1536.500000         0.003313526       697.551698813
      3074         1537.000000         0.003476351       731.829047391
      3075         1537.500000         0.003472049       730.923409677
      3076         1538.000000         0.003333209       701.695321066
      3077         1538.500000         0.003153364       663.834925398
      3078         1539.000000         0.003034701       638.854429382
      3079         1539.500000         0.003026153       637.054856190
      3080         1540.000000         0.003093963       651.330091922
......
    The last column is temperature. Could anyone help me? I would be very appreciated!
    With my best regards,
    Junbo


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