Is the energy converged in NVE simulation?

[zuohen... at gmail.com]

Hi,

I did a simulation with NVE ensemble. The energy plot is shown in figure 
(Energy.jpg).
The plot should be flat one in NVE simulation, but my plot has a 
fluctuation.
Is there any problem in my input file (attached file)?   
Is the energy converged? Is the fluctuation reasonable?

Could anyone give me some suggestions?
Thank you very much.

Best wishes,
Zuoheng

在 2018年9月13日星期四 UTC+2下午4:23:29，zuoh... at gmail.com写道：
>
> Hello everyone,
>
> Recently, I want to confirm the suitable time step, when I use core shell 
> model for OH- ions and SPC/Fw for water molecules. 
> I have tested if I use core shell model for water, 1 fs of time step is 
> too large. The energy of NVE simulation is not converged significantly.
> However, after I transfered the SPC/Fw to replace the core-shel model for 
> water, the energy of NVE simulation seemed to be converged (shown in 
> figure, blue line for the energy plot and orange line for the averaged 
> energy).
> There are 1 Fe3+, 3 OH-(core shell model) and 28 water molecules(SPC/Fw) 
> in the system. 
> I am not sure if the energy is converged? or the fluctuation is too 
> strong? 
> If it is converged, can I use 1 fs of time step to do next simulation?
> Could anyone give me some suggestions?
>
> Thank you very much!!
>
> Best,
> Zuoheng  
>
> [image: Fe3OH3.png]
>
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