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Re: [ESPResSo] constraints and nemd
From: |
Jens Smiatek |
Subject: |
Re: [ESPResSo] constraints and nemd |
Date: |
Mon, 29 Mar 2010 12:54:45 +0200 (CEST) |
Dear Guillaume,
1.) Negative values for the plane cell command indicate zero spatial
dimension. The value of -10 is chosen arbitrarily.
For example:
constraint plane cell -1 5 -7 type id
indicates an infinite wall at y=5 sigma position with no components in x
and z-direction.
The reason for that usage is the possibility to model structured
microchannels.
Your examples:
For x1,2 and y1,2 use negative chosen arbitrary values like -1,-2,-3,...
The problem:
Make sure that all particles are inside the channel confined between both
two walls and outside the
cutoff-range of the LJ-potential. Otherwise you'll receive error mesaages
like 063.
2.) The tunable-slip boundaries can only be used with the constraint cell
command.
3.) The viscosity can be calculated by a Plane Poiseuille flow and the
tunable-slip boundaries method. Check the corresponding literature at the
end of the paragraph of the ug.
Best regards,
Jens
==========================================
Jens Smiatek
Institute of Physical Chemistry
Room E0-002
Tel.: 0049-251-83-29154
email: address@hidden
Institut fuer Physikalische Chemie
Corrensstrasse 28/30
D-48419 Muenster
Germany
==========================================
On Thu, 25 Mar 2010, Guillaume Larsen wrote:
>
> dear all,
>
> i have several questions concerning the 'constraint plane cell' feature:
> 1) the definition of this constraint doesn't seem really clear to me,
> 'constraint plane cell x y z type id'
> the example from the manual:
> create an in???nite plane in z -direction at z = 20.0 of type id 1, use:
> constraint plane cell -10 -10 20 type 1
> to define a plane, one should need a normal vector and a position from
> origin, but here we only have 3 parameters x, y and z to configure. What do
> represent the '-10' for x and y in the command.
> I want to define two planes: which values for x1,2 and y1,2 should I use to
> define the planes below?
> constraint plane cell $x1 $y1 $box_l_i type $wall_type ---> normal
> z-direction at z=$box_l_i
> constraint plane cell $x2 $y2 0 type $wall_type ---> normal z-direction
> at z=0
> So far, i picked different values for x and y, but ESPResSo returns error
> messages about plane constraint violation (error 063) at warm up phase.
>
> 2)is it possible to use the tunable slip interaction command associated to a
> 'constraint wall' command?
>
> 3)I have been having problems recently with the use of the nemd feature, and
> i think the misuse of 'constraint plane cell' is the reason. The fact is that
> I want to use the nemd feature to compute the viscosity of the system. Two
> 'constraint plane cell' have to be defined before using the command 'nemd
> viscosity', is it right?
>
> Thank you in advance for your answers!
>
> best regards,
>
> Guillaume
>
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