[gmx-users] Positive and negative ions move in the same direction under a constant electric field?

[Mark Abraham]

Tom Weingarten wrote:
> I'm not sure if this has been addressed previously, but perhaps the 
> reason why we're seeing so many users performing incorrect temperature 
> coupling of ions is because that is how it is done in the very popular 
> fwspider tutorial. In fact this tutorial is the first hit on google for 
> "gromacs tutorial."
> 
> ; Berendsen temperature coupling is on in three groups
> Tcoupl              =  berendsen
> tau_t               =  0.1          0.1  0.1
> tc_grps             =  protein      sol  CL­
> ref_t               =  300          300  300
> 
> http://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fwww2.umdnj.edu%2F~kerrigje%2Fpdf_files%2Ffwspidr_tutor.pdf&ei=wuZBRpz3IZDOwQKZqaT5DQ&usg=AFrqEzdUTsDP3qQxqY90ZIlZ2PrpLg8FXg&sig2=3IIJaY71ZM6wMwWtUAE5AA 
> <http://www.google.com/url?sa=t&ct=res&cd=1&url=http%3A%2F%2Fwww2.umdnj.edu%2F~kerrigje%2Fpdf_files%2Ffwspidr_tutor.pdf&ei=wuZBRpz3IZDOwQKZqaT5DQ&usg=AFrqEzdUTsDP3qQxqY90ZIlZ2PrpLg8FXg&sig2=3IIJaY71ZM6wMwWtUAE5AA>
> 
> Hopefully this is useful, my apologies if I'm not understanding the 
> issue correctly.

No, you're the first with a good explanation why this might be
happening. Nobody's been game to say where they got the idea for their
coupling schemes :-) Does someone with some clout wish to suggest to
Kerrigan that he use

; Berendsen temperature coupling is on in three groups
Tcoupl              =  berendsen
tau_t               =  0.1          0.1
tc_grps             =  protein      non-protein­
ref_t               =  300          300

in his tutorial? This actually simpler for him, rather than specifying
different things when Cl is absent and present.

Mark