Beschreibung
The role played by earth sciences in the scientific community has changed considerably during this century. Since the revolutionary discoveries of global processes such as plate tectonics, there has been an increasing awareness of just how fundamental many of the mechanisms which dominate in these processes depend on the physical properties of the materials of which the earth is made. One of the prime objectives of mineral sciences is now to understand and predict these properties in a truly quantitative manner. The macroscopic properties which are of most immediate interest in this context fall within the conventional definitions of thermodynamics, magnetism, elasticity, dielectric susceptibilities, conductivity etc. These properties reflect the microscopic contributions, at an atomistic level, of harmonic and anharmonic lattice vibrations, ionic and electronic transport as well as a great variety of ordering and clustering phenomena. The advances made by solid state physicists and chemists in defining the underlying phenomena lnvolved in the thermal evolution of materials have stimulated major new research initiatives within the Earth Sciences. Earth Scientists have combined to form active groups within the wider community of solid state and materials scientists working towards a better understanding of those physical processes which govern not only the behaviour of simple model compounds but also that of complex materials like minerals. Concomitant with this change in direction has come an increasing awareness of the need to use the typical working tools of other disciplines.
Autorenporträt
Inhaltsangabe1. 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.- 5.
