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## [ESPResSo] wall normal & box simulation (basic questions)

 From: Salvador Herrera Velarde Subject: [ESPResSo] wall normal & box simulation (basic questions) Date: Fri, 19 Jun 2009 12:38:49 -0400

Dear All,

I think that my problems with the wall normal constraints come also from my misunderstanding of the primary simulation box in ESPResS

In the user's mail list I found that the primary simulation box is not centered at (0,0,0) .
So the origin of the simulation box is in one of the corners?  That means, that I can't place a wall normal constraint at negative distances, right?

Besides, If I put the particles inside the simulation box in a lattice considering that is centered at (0,0,0) ( see below),  is it this wrong in ESPResSO?
==========================================================
# first particle (all negative coordinates)
set posx [expr { -1.0 * ( \$bl - \$delta ) / 2.0 } ]
set posy [expr { -1.0 * ( \$bl - \$delta ) / 2.0 } ]
set posz [expr { -1.0 * ( \$bl - \$delta ) / 2.0 } ]
part 0 pos \$posx1 \$posy1 \$posz1 type 0 q \$zeff

for {set i 1 } { \$i < \$np } { incr i } {
set posx [expr { \$posx + \$delta} ]
set posy \$posy
set posz \$posz
part \$i pos \$posx \$posy \$posz type 0 q \$zeff
if { \$posx > \$bl/2.0 } then {
set posx \$posx1
set posy [expr { \$posy + \$delta} ]
set posz \$posz
part \$i pos \$posx \$posy \$posz type 0 q \$zeff
if { \$posy > \$bl/2.0 } then {
set posx \$posx1
set posy \$posy1
set posz [expr { \$posz + \$delta} ]
part \$i pos \$posx \$posy \$posz type 0 q \$zeff
}
}
}

could you help me to clarify these points?

Thanks a lot for your time,