Low-temperature phase diagrams: non-linearities due to quantum mechanical saturation of order parameters

At low temperatures, the behaviour of structural phase transitions is modified by the influence of quantum fluctuations. Such fluctuations enhance the stability of the high-symmetry phase, reducing the observed transition temperature. The effect on phase diagrams of temperature versus some other control parameter (e.g. pressure or chemical composition) is described. A simple low-temperature extension of Landau theory is used, where the extent of quantum mechanical effects is characterized by a saturation temperature . The theory is used to model the phase diagrams of the mineral anorthoclase , the ferroelectric materials ( for the 20 K transition), and SbSI . The saturation temperature is related to the extent to which changes in the hard phonon modes influence the transition mechanism.

[1]  S. A. Hayward,et al.  Displacive phase transition in anorthoclase: The “plateau effect” and the effect of T1-T2 ordering on the transition temperature , 1996 .

[2]  S. Redfern,et al.  Order parameter saturation (plateau effect) as a function of composition in the sanmartinite (ZnWO4)-Cuproscheelite (CuWO4) solid solution , 1996 .

[3]  E. Salje,et al.  Phonon spectra of alkali feldspars: Phase transitions and solid solutions , 1996 .

[4]  E. Salje.  Chemical mixing and structural phase transitions: the plateau effect and oscillatory zoning near surfaces and interfaces;Chemical mixing and structural phase transitions: the plateau effect and oscillatory zoning near surfaces and interfaces , 1995 .

[5]  Their Reactions,et al.  Feldspars and their reactions , 1994 .

[6]  V. Heine,et al.  On the application of mean-field and landau theory to displacive phase transitions , 1992 .

[7]  E. Salje.  Application of Landau theory for the analysis of phase transitions in minerals , 1992 .

[8]  M. Carpenter.  Thermodynamics of phase transitions in minerals: a macroscopic approach , 1992 .

[9]  E. Salje,et al.  Order parameter saturation at low temperatures -numerical results for displacive and O/D systems , 1991 .

[10]  R. Piltz,et al.  High-pressure neutron-diffraction studies of KH2PO4-type phase transitions as Tc tends to ok , 1991 .

[11]  Ekhard K. H. Salje,et al.  Order-parameter saturation and low-temperature extension of Landau theory , 1991 .

[12]  Simon A. T. Redfern,et al.  Thermodynamics of plagioclase III: Spontaneous strain at the $$I\overline 1 - P\overline 1$$ phase transition in Ca-rich plagioclase , 1988 .

[13]  E. Salje,et al.  Spontaneous strain at the structural phase transition in NaNO3 , 1988 .

[14]  Joseph V. Smith,et al.  Crystal Structures, Physical, Chemical, and Microtextural Properties , 1988 .

[15]  H. Uwe,et al.  Stress-Induced Quantum Ferroelectricity in SrTiO3 , 1987 .

[16]  S. Hoshino,et al.  Structural transitions in Mo8O23 , 1986 .

[17]  U. Bismayer,et al.  Effect of strain-induced order-parameter coupling on the ferroelastic behaviour of lead phosohate-arsenate , 1986 .

[18]  S. Kieffer.  Chapter 3. HEAT CAPACITY and ENTROPY: SYSTEMATIC RELATIONS to LATTICE VIBRATIONS , 1985 .

[19]  P. Bastie,et al.  γ-ray diffraction in the vicinity of a ferroelastic transition: application to 'real crystal' of RbH2PO4 and KH2PO4 , 1984 .

[20]  G. Samara,et al.  The Study of Soft-Mode Transitions at High Pressure , 1982 .

[21]  H. Bilz,et al.  Dielectric susceptibility in quantum ferroelectrics , 1980 .

[22]  T. Schneider,et al.  Quantum effects in an n -component vector model for structural phase transitions , 1976 .

[23]  H. Uwe,et al.  Electrostriction and Stress-Induced Ferroelectricity in KTaO3 , 1975 .

[24]  G. Samara.  Effects of pressure on the dielectric properties of and the vanishing of the ferroelectricity in SbSI , 1975 .

[25]  H. Cummins,et al.  Brillouin-scattering study of the elastic anomaly in ferroelectric KH2PO4 , 1974 .

[26]  G. Samara.  Vanishing of the Ferroelectric and Antiferroelectric States in KH 2 PO 2 -Type Crystals at High Pressure , 1971 .

[27]  W. J. Burke,et al.  Stress induced ferroelectricity in SrTiO3 , 1971 .

[28]  K. Müller,et al.  Characteristic Structural Phase Transition in Perovskite-Type Compounds , 1968 .

[29]  R. Cowley.  Temperature Dependence of a Transverse Optic Mode in Strontium Titanate , 1962 .