Structural Phase Transitions I

ISBN-13: 9783642815331 / Angielski / Miękka / 2011 / 192 str.

K. a. M. Ller; H. Thomas

Opis

The growth and maturity of research in structural phase transitions (SPT) make it an appropriate subject for the Topics in Current Physics series. The maturing pro- cess is, however, by no means complete. New areas such as incommensurable SPT, quasi-low-dimensional systems, systems containing lattice disorder due to impuri- ties or as mixed crystals, multicritical points, and quantum effects have recently come under focus. The understanding of the dynamics, be it microscopic soft-mode theory or critical dynamics, more specifically the central-peak problem, is also still quite incomplete. On the other hand, there are areas which are genuinely conso 1 ida ted. On the theoreti ca 1 s ide~ these concern symmetry properti es, Landau theory, and the application of static renormalization theory to critical phenomena. ,Also, the use of various complementary experimental techniques, with their specific merits, are well in hand. The field of STP's and of the various methods of investigation range so widely that it appeared appropriate to invite a number of scientists to review their respective areas of experti se to which they have made s i gnifi cant contri butions.

Spis treści

1. Introduction.- References.- 2. Optical Studies of Structural Phase Transitions.- 2.1 Background.- 2.1.1 Phase Transitions in Solids: Definitions.- 2.1.2 Symmetry Classification of Optical Techniques.- 2.2 Experimental Techniques.- 2.2.1 Absorption and Fluorescence.- a) IR Absorption and Reflection.- b) Optical Absorption and Fluorescence.- 2.2.2 Birefringence.- a) Typical Experimental Apparatus.- 2.2.3 Light Scattering.- a) General Background.- b) Scattering from Coupled Modes.- c) Critical Exponents and Soft Mode Spectra.- d) Intensity of Scattering.- e) Grating Spectroscopy.- f) Interferometry.- g) Recent Advances of Technique.- 2.3 Ferroelastic Transitions.- 2.3.1 Cooperative Jahn-Teller Systems.- 2.3.2 PrAlO3: A Prototypical CJT System.- 2.4 Nonpiezoelectric Ferroelectric: Pb5Ge3O11.- 2.5 Piezoelectric-Ferroelectric Transition in KDP and Its Isomorphs.- 2.5.1 Coupled Modes i n the Raman Spectrum.- 2.5.2 Brillouin-Raman Spectra.- 2.5.3 Static and Dynamic Central Peaks.- 2.6 Zone Boundary Phase Transitions (Antiferrodistortive).- 2.6.1 Systematics in the Fluoroperovskites.- 2.6.2 Recent Results in SrTiO3.- 2.7 Zone Boundary Ferroelectrics: The Molybdates.- 2.8 Incommensurate Phase Transitions.- 2.8.1 Charge-Density Waves: TaSe2.- 2.8.2 Incommensurate-Ferroelectric: K2SeO4.- 2.8.3 Ferroelectric-Antiferroelectric: BaMnF4.- 2.9 Nonlinear Optical Studies of Phase Transitions.- 2.10 Renormalization Group Theory and Multicritical Phenomena.- 2.11 Concluding Remarks.- References.- 3. Investigation of Structural Phase Transformations by Inelastic Neutron Scattering.- 3.1 Inelastic Neutron Scattering.- 3.1.1 General Aspects.- 3.1.2 Structural Changes with Small Displacements.- 3.1.3 Soft Modes.- 3.2 The Central-Peak Phenomenon.- 3.3 Molecular Crystals.- 3.3.1 The Elastic Incoherent Structure Factor (EISF).- 3.3.2 High-Resolution Instruments.- a) The Backscatteri ng Spectrometer.- b) The Four Chopper Time-of-Flight Spectrometer.- c) The Neutron Spin-Echo Spectrometer.- 3.3.3 Dynamics of Molecular Crystals.- a) Librations.- b) Rotational Reorientation of a Single Molecule.- c) Translational Lattice Vibrations.- d) Soft Modes and Relaxation of Clusters.- 3.4 Incommensurable Structures.- 3.4.1 Amplitude and Phase Modes.- 3.4.2 Conducting Materials.- 3.4.3 Insulating Materials.- References.- Additional References with Titles.- 4. Ultrasonic Studies Near Structural Phase Transitions.- 4.1 Background Material.- 4.1.1 Elastic Response Functions and Their Measurement.- a) Pulse Method.- b) CW Methods.- c) Low-Frequency Methods.- 4.1.2 Connection to Processes Characterizing the Phase Transition.- 4.2 Theoretical Analysis.- 4.2.1 Landau Theory.- 4.2.2 Symmetry Aspects.- 4.2.3 Mode-Mode Coupling and Scaling.- 4.2.4 Renormalization Group Analysis.- 4.3 Experimental Results.- 4.3.1 Strain Is Order Parameter.- a) Ferroelectrics.- b) Other Nonelectronic Compounds.- c) Cooperative Jahn-Teller Transitions.- d) Band Jahn-Teller Transitions.- e) Mixed Valence Transitions.- f) Martensitic Phase Transformations.- 4.3.2 Strain Is Not Order Parameter.- a) Phonon Coordinate Is Order Parameter.- b) Electric Polarization Is Order Parameter.- c) Orientational Degree of Freedom Is Order Parameter.- d) Charge-Density Wave Transitions.- e) Solid Electrolytes.- f) Incommensurate Phases.- 4.4 Summary.- References.- Additional References with Titles.