[gmx-users] How to set the friction coefficient in BD?

[Hanming]

Dear All, 

When I do the BD simulation I want to know how to set the value of friction
coefficient. Should I need to determine it according to the viscosity of
the solvents such as water and alcohol. Or should I try some value first in
BD, then get some property of the system and compare it with experiment
value?
I read some pages in Hess's book. He said like this:"In Brownian dynamics
the friction coefficient scales the time. This means that one
only needs to perform a simulation at one value of friction coefficient .
Afterwards the time of the results can be scaled to obtain results for any
value of friction coefficient ."
I did not catch the meaning of it. Does it mean that only one friction
coefficient is ok? However, different solvents have different property,
right? How can I get the differences if I just set one friction coefficient
in BD simulation? 

Thx a lot. 

Ming