  The microscopic model in which nodes interacting with each other are
statistical systems is introduced. The nodes conditions are connected with a
string of distinct microscopic configurations and depend on external parameters
(pressure and temperature). In this model the consequent description of first-
and second-order phase transitions is carried out and their microscopic level
distinctions are analyzed. It is shown that first-order transitions occur when
the configuration entropy change at nodes under transitions from dipole-active
(low-symmetric) state to symmetric one is more than ln4. Otherwise the
second-order transitions take place.
