Read atomic force from 
<a href="http://cms.mpi.univie.ac.at/vasp/vasp/vasp.html">VASP</a> OUTCAR file.
The file name has to be <tt>OUTCAR</tt> and must be in the current directory
(specified by <tt>dirname</tt>).

<p>
Also see <tt>readPOSCAR</tt>.

