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

[Salvador Herrera Velarde]

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,
 
 Salvador