Thank you for your prompt replies.
For example, if
you have a bond length of 4 and a box size of 4, then
there can be many periodic images of the atom J that I is
bonded to that are close to I. Which one is it bonded to?
You mean that LAMMPS does not discern between
"original" atom and its images?
The safe thing
is not to have a cutoff distance greater than the box size
minus a bond length.
Thank you, this does work!
(I've increased the box to 12 x 12 x 12 A and set the cutoff distance to 8.0; everything was o'k)
However, the problem is that I usually work with "acicular"
boxes: typical dimensions 6 x 6 x 50 A.
So I need to make a cutoff distance 6 A minus, say, 2 A
as bond length = 4 A.
As I understand this, for Ewald calculations this cutoff distance means the "boundary" between real-space and
Up to my experience, so small cutoff distances (as 4 A) lead to
substantial decay of both computational efficency and accuracy
of Ewald calculations.
Hence I would ask you to patch LAMMPS in order to allow cutoff distances greater than minimum box dimension.
I hope you will find a time for this.
Thank you very much in advance!