The debye-waller factor and structural phase transitions

Abstract

As continuous structural phase transitions are approached, an increase in both the Debye-Waller factor and the nuclear quadrupole coupling coefficient is predicted. The behaviour of these is dependent upon the nature of the fluctuations associated with the structural phase transition. In particular in uniaxial ferroelectrics the macroscopic electric field suppresses some of the fluctuations so that the Debye-Waller factor has a form different from that at other phase transitions. It is shown that the predicted form for uniaxial ferroelectrics is consistent with the observed temperature dependence of the quadrupole resonance in CsDA when reasonable values are used for the parameters in the theory. At other phase transitions the measurement of the Debye-Waller factor would enable the critical exponent, γ, to be determined and compared with the various predictions of renormalization group theory.