INFLUENCE OF SYMMETRY-BREAKING DEFECTS ON FIRST-ORDER STRUCTURAL PHASE-TRANSITIONS

The influence of symmetry-breaking (''random local field'') defects on first order structural phase transitions is studied both within the L andau theory and in the case when the first order nature of transition is due to the order parameter fluctuations. It is shown that in the b oth cases the temperature of the transition decreases but the disconti nuity of the order parameter at the transition increases due to the pr esence of the defects. Nevertheless the equilibrium value of the order parameter at a given temperature is less in the impure crystall than in the pure one, i.e., the phase transition is smeared.