Conjugate gradient relaxation with a selected set of atoms constrained in the 
hyperplane perpendicular to <tt>SR2 - SR1</tt>.

<p>
Example: <tt>MD++/scripts/CSD-book/chap7/sect7.3/si-kink-cstmep.script</tt>

<p>
For details, see <a href="http://micro.stanford.edu/~caiwei/CSD-Book/">Computer Simulations
of Dislocations</a>, Chapter 7, Section 7.3.


<p>
Also see <tt>relax</tt>, <tt>constrainatoms</tt>.
