We consider heavy neutral atoms of atomic number Z modeled with kinetic
energy (c2p2+c4)1/2βc2 used already by Chandrasekhar. We study the
behavior of the one-particle ground state density on the length scale Zβ1
in the limit Z,cββ keeping Z/c fixed. We give a short proof of a
recent result by the authors and Barry Simon showing the convergence of the
density to the relativistic hydrogenic density on this scale