Usage: <tt>input = [ <i>j_des j_src</i> ]  moveRchain</tt>

<p>
Copy atomic positions in replica <tt><i>j_src</i></tt> to replica <tt><i>j_des</i></tt>
in array <tt>Rc</tt>.

<p>
Also see <tt>initRchain</tt>, <tt>copyCNtoRchain</tt>.
