ABSTRACT
To establish the general relationships of the polymorphism of elements and compounds and the thermodynamic and kinetic conditions for the synthesis of new high-pressure phases, it is of greatest interest to consider cases in which the application of pressure results in modification not known in this material at normal pressure. Such modifications are ε-modification of iron, ω-modifications of titanium and zirconium, the metallic high-pressure modification of germanium, silicon, etc. The interest here is how to establish areas of the stable existence of high-pressure modifications, the equilibrium properties of high-pressure phases, which can be used to calculate the T-p-c diagrams of systems based on these substances, as well as the kinetics of transformations of the modifications at the normal pressure to the highpressure phase, and back. The latter, in addition to the total value for the detection of regularities of the kinetics of polymorphic transformations, also represents a very specific interest in establishing the conditions for obtaining and maintaining the new phases at normal pressure (‘synthesis’).
