[CP2K-user] [CP2K:14560] AIMD simulation of a single water molecule

[Marcella Iannuzzi]

Dear Junbo, 

You can, but as Matthias has said, the temperature fluctuations are going 
to be large
Regards
Marcella


On Saturday, January 16, 2021 at 9:28:57 AM UTC+1 lu... at gmail.com wrote:

> Hi Krack,
>   Thank you very much for your comment. Yeah, I just need to do a test to 
> calculate vibrational density of state for a single water molecule. Could I 
> just do a NVE simulation fo a single water molecule.
>    With my best regards,
>    Junbo
>
> Krack Matthias (PSI) <mat... at psi.ch> 于2021年1月15日周五 下午10:13写道：
>
>> 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:* c... at googlegroups.com <c... at googlegroups.com> *Im Auftrag von *Junbo 
>> Lu
>> *Gesendet:* Freitag, 15. Januar 2021 13:03
>> *An:* cp2k <c... 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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