[gmx-users] the temperature effect in the simulation

[Nicolas Sapay]

He, Yang wrote:
> Hi all users,
>
> When I change the temperature to try to get different disassociation about the two DNA's strands. But even I change the value of temperature by 0K in the mdp file ,
>
> ; OPTIONS FOR WEAK COUPLING ALGORITHMS
> ; Temperature coupling
> Tcoupl                   = berendsen
> ; Groups to couple separately
> tc-grps                  = System
> ; Time constant (ps) and reference temperature (K)
> tau_t                    = 0.001
>   
The coupling constant sounds a bit small. The dynamics of fast motions 
may be affected more than you want, but I'm not a specialist of DNA and 
I don't know if it's a problem in that particular case.
> ref_t                    = 300
>   
This indicates that your target temperature is 300K not 0K
> ; Pressure coupling
> Pcoupl                   = no
> Pcoupltype               = isotropic
> ; Time constant (ps), compressibility (1/bar) and reference P (bar)
> tau_p                    = 0.5
> compressibility          = 4.5e-5
> ref_p                    = 1.0
> ; Random seed for Andersen thermostat
> andersen_seed            = 815131
>
> It  will also disassociate .It is strange.
>
> Can anyone of you tell me what is the reason for that?
>
> Thank you in advance.
>
> Yang
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>   

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