[ESPResSo] constraints and nemd

[Guillaume Larsen]

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 infinite 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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