[ESPResSo-devel] shifted periodicity

[Ivan Cimrak]

Dear all,


Periodicity of the simulation box is implemented in a way that, e.g.
for the lbfluid, the following periodic condition is valid:
v(x, y, z) = v(x+boxX, y, z), similarly in other directions.

I need to implement shifted periodicity, something like this:
Let shiftY be a number between 0 and boxY indicating the shift in y
direction. The shifted periodicity condition would then be
v(x,y,z) = v(x+boxX, y + shiftY, z)
It could of course be even more complicated, with simultaneous shift
also in z direction, but for brevity let us keep it simple like above.


This shifted periodicity must of course be implemented also for
particles. Currently, two particles with very short-range interaction
(with cut_off e.g. 3*delta) feel each other in case their positions
are  e.g. (x+delta, y, z) and (x+boxX-delta, y,z). In case with
shifted periodicity, particles with these positions would not feel
each other, however, particles with positions (x+delta, y, z) a
(x+boxX-delta, y + shiftY,z) would do.


Can anyone give a reasonable estimate on how difficult it is to
implement something like this? And also, where in the code to look:-)

Thank you,
Ivan




-- 
Ivan Cimrak
FRI Zilinska Univerzita v Ziline
personal web: http://www.kst.fri.uniza.sk/~icimrak/
cell-in-fluid group: http://cell-in-fluid.fri.uniza.sk