  A microscopic picture of the ``preparation'' of a crystal to the transition
to liquid state at the approach to melting temperature is proposed. Basing on
simple crystallogeometric considerations and the analysis of the computational
results for corresponding anharmonic characteristics an evaluation is given for
the magnitude of atomic displacements leading to the appearance of close packed
Bernal pseudonuclei in the solid phase. A physical meaning of the classical
Lindeman criterion and the mechanisms of the formation of free volume in the
crystal phase are discussed.
