Physical Properties and Thermodynamic Behaviour of Minerals

Inhaltsverzeichnis

1. The Microscopic Mechanisms of Complex Structural Phase Transitions.- 1. Introductory remarks.- 2. Microscopic mechanisms.- 3. Computer modelling.- 4. The Landau free energy function.- 5. Critical fluctuations.- References.- 2. The Thermodynamics of Short Range Order.- 1. Introduction.- 2. Symmetry Principles for interactions in modulated structures.- 2.1 Symmetry groups and their irreducible representations.- 2.2 The origin of selection rules for interactions.- 2.3 The nature of irreducible representations of the space group.- 2.4 Symmetry criteria for the interaction of modulation components.- 2.5 Summary of the theory of short range interactions in crystals.- 3. The group theoretical description of short range order in crystals.- 3.1 Long range order and the importance of the special point vectors.- 3.2 The general characteristics of short-range order.- 3.3 The development of an energy band theory for short range order.- 3.4 The nature of interband interactions in order-disorder.- 3.5 Ordering modulations associated with an invariant point.- 3.6 The interaction between ordering and phonon bands.- 3.7 Summary of stable order modulations in crystals.- 4. Short range order interactions in incommensurate structures.- 4.1 Feldspars.- 4.2 The ordering behaviour in mullite.- 4.3 The ordering interactions in yoderite.- 5. Order-phonon modulation structures in minerals.- 5.1 The order-phonon modulated structure of potassium feldspar.- 5.2 Order-phonon interactions in modulated cordierite.- 6. Thermodynamic aspects of the occurrence of modulated structures.- 6.1 Thermodynamically stable order-modulated structures.- 6.2 Order-modulation in the mechanism of order-disorder transitions.- 7. References.- 3. Incommensurability in Two Classes of Solids: Modulated Insulators and Quasicrystalline Alloys.- 1. Introduction.- 2. Characterization of incommensurate crystals: "Standard" behaviour.- 3. Incommensurate phase transition: the "soft-mode" precursor effect.- 4. Specific dynamic properties of incommensurate phases: "phasons".- 5. Present situation concerning the static properties of incommensurate phases.- 5.1 Some examples of experimental typical phase diagrams.- 5.2 Other specific properties: global hysteresis, satellite broadening.- 5.3 Discussion.- 6. Quasicrystals.- References.- 4. Structural Phase Transitions and Specific Heat Anomalies.- 1. Introduction.- 2. Experimental methods.- 2.1 Scanning calorimetry.- 2.2 AC calorimetry.- 2.3 Adiabatic calorimetry.- 3. Reduction of background heat capacities.- 4. Application of Landau theory.- 5. Fluctuations of the order parameter and critical exponents.- 6. The influence of lattice imperfections.- 7. Order parameter coupling and excess specific heats.- 8. Coupled order parameters in feldspar.- 8.1 Na-feldspar.- 8.2 Ca-feldspar.- 9. Selected examples of structural phase transitions.- 10. Charge carrier induced structural phase transitions.- References.- 5. What Can Spin Models Tell Us About the Behaviour of Minerals?.- 1. Introduction.- 2. Universality and phase diagrams.- 3. Modulated structures.- 4. Surfaces and interfaces.- References.- 6. New Developments in Raman Spectroscopy on Structural Phase Transitions.- 1. Introduction.- 2. Theory.- 3. Applications of hard mode Raman spectroscopy.- 3.1 Displacive phase transitions and evidence for Na-K site ordering in alkali feldspar - experimental part.- 3.2 Phase transitions and order parameter treatment in feldspars.- 3.3 Phase transition in ferroelastic As2O5.- 3.4 Raman scattering of hard modes in stepwise phase transitions in Pb3(P1-xAsxO4)2.- 3.5 Sodium nitrate.- 3.6 Magnesium cordierite.- 4. Conclusions.- 5. References.- 7. Linear and Circular Birefringence and Crystal Structures.- 1. Introduction.- 2. Linear birefringence.- 2.1 Methods of measurement.- 2.2 Applications to crystals.- 3. Circular birefringence.- 3.1 Measurement and observation.- 3.2 Relationship to crystal structure.- 3.3 Calculation of optical rotation.- 4. Summary.-