C6 coefficients using Thomas-Fermi + vonWeizsaeker approximation for the
kinetic energy functional is implemented in atomic code.
A directory with some examples is added in atomic_doc
Contributed by Huy-Viet Nguyen (SISSA).
git-svn-id: http://qeforge.qe-forge.org/svn/q-e/trunk/espresso@2510 c92efa57-630b-4861-b058-cf58834340f0