Re: [ESPResSo-users] virtual sites questions

[Jiajia Zhou]

Thanks, Rudolf!

I'm just wondering if there are people working on the raspberry model
coupled to solvents using DPD or LB? I'm working on a similar project
and would like to have people to bounce ideas with.

Thanks!
Jiajia


On 24 March 2011 12:46, Rudolf Weeber <address@hidden> wrote:
> Hello,
> On Mon, Mar 21, 2011 at 11:33:02PM +0100, Jiajia Zhou wrote:
>> I am trying to use the raspberry model to simulate colloids. I found
>> the VIRTUAL_SITES_RELATIVE (in developer's code) is very handy, ie, I
>> create a single particle at the center of a sphere, and then decorate
>> the surface with virtual sites. But there are still some question I'm
>> wondering if some one can help me.
>>
>> 1)  I'm using the Langevin thermostat. I read in the ug file that
>> there is an additional feature called VIRTUAL_SITES_THERMOSTAT. Do we
>> need to turn on this feature in order to have the frictional and
>> random force on the virtual sites? I tried to uncomment the line in
>> the configuration but doesn't seem to do anything.
> You have two options regarding the thermostat,
> Either, you thermostat the rotation and translation of the centrl particle. 
> This is the standard behaviour.
> Or you do not thermostat the central particle and instead thermostat all the 
> virtual particles. This is currently only implemented for the case that there 
> are no other real particles to thermostat. You can achieve this behaviour by 
> setting
> THERMOSTAT_VIRTUAL_SITES and THERMOSTAT_IGNORE_NON_VIRTUAL.
>
>
> The difference between those two options lies in a different effective gamma, 
> i.e. relaxation time for the rotational motion of your raspberry. If you are 
> not interested in dynamical properties, you can therefore safely chose the 
> first option.
>
>
>
> Please note that the thermostatting switches for virtual sites have not yet 
> been implemented for Lattice-Boltzmann and dpd. If you want to couple the 
> raspberry to an explicit fluid simulation, this coupling should definitely 
> act on the virtual particles.
>
> Hope that helps!
> Regards, Rudolf
>
>