  Precise solutions of the Hartree-Fock equations for the ground state of the
hydrogen molecule are obtained for a wide range of internuclear distances R by
means of a two-dimensional fully numerical mesh computational method. The
spatial parts of the single-electron wave functions are found to be coinciding
for R<2.30a.u. At larger distances they become different and as R->\infty each
of them takes the form corresponding to a separate atom. This quantum phase
transition occurring at R=2.30a.u. gives a natural boundary between a
delocalized behavior of electrons in the molecule and their distribution over
separate atoms. This phenomenon can be also considered as an analog of the
Wigner crystallization or the Mott transition on the level of a single
molecule.
