document how using shrink-wrap boundaries can cause lost atoms in parallel

For style {s}, the position of the face is set so as to encompass the

atoms in that dimension (shrink-wrapping), no matter how far they

move.

move. Note that when the difference between the current box dimensions

and the shrink-wrap box dimensions is large, this can lead to lost

atoms at the beginning of a run when running in parallel. This is due

to the large change in the (global) box dimensions also causing

significant changes in the individual sub-domain sizes. If these

changes are farther than the communication cutoff, atoms will be lost.

This is best addressed by setting initial box dimensions to match the

shrink-wrapped dimensions more closely, by using {m} style boundaries

(see below).

For style {m}, shrink-wrapping occurs, but is bounded by the value

specified in the data or restart file or set by the