Structural phase transformations in nonstoichometric compounds

Consideration is being given to modern state of investigation into phase transitions of order-disorder in nonstoichiometric compounds of interstitial phase type. Distribution functions of interstitial atoms were calculated. Method of order parameter functional for describing order-disorder transitions was discussed. Method application was illustrated by calculations of atomic ordering in nonstoichiometric carbides of niobium and tantalum. Ordering effcet on niobium carbide properties was considered