This volume in Advances in Physical Geochemistry presents the latest synthesis of theory and experimental data pertaining to structural and magnetic phase transitions in a variety of geochemically important minerals. The book is the first to cover the impact of this rapidly progressing area of solid state physics in earth sciences and reflects its growing significance for mineralogy and petrology.
This work comprises studies of structural phase transitions (SPT's) in three different phases (anorthite CaAl$sb2$Si$sb2$O$sb8$, Sr$sb2$SiO$sb4$, and AlPO$sb4$-cristobalite) via high-resolution nuclear magnetic resonance spectroscopy using mostly magic-angle spinning (MAS) techniques. The results provide important insight into each of these SPT's and illustrate the types of information that can be obtained about SPT's using MAS NMR spectroscopy. Insight regarding structural changes for all three phases was obtained from the temperature dependence of the chemical shift. In Chapter 1 the temperature variation of the modulation wave in the incommensurate phase of Sr$sb2$SiO$sb4$ is determined from $sp{29}$Si MAS NMR spectra. In Chapter 2 changes in the $sp{29}$Si chemical shifts of anorthite show that its alumino-silicate framework transforms displacively at the P1-I1 transition. In Chapter 3 comparison of the $sp{31}$P and $sp{27}$Al chemical shifts of the $alpha$ and $beta$ phases of AlPO$sb4$-cristobalite indicates that the $beta$ phase is dynamically disordered. For anorthite and Sr$sb2$SiO$sb4$ the chemical shifts also provide a measure of the temperature evolution of the order parameter within the context of Landau theory. The ability of these methods to provide dynamical information from chemical shifts is demonstrated for $beta$-AlPO$sb4$-cristobalite for which time-averaging of chemical shifts produces values different than expected from the crystal structure, and for Sr$sb2$SiO$sb4$, for which the results show that the modulation wave is pinned up to 200$spcirc$C. For anorthite and AlPO$sb4$-cristobalite the chemical shift results are supplemented by spin-lattice relaxation measurements ($sp{29}$Si in anorthite, $sp{31}$P and $sp{27}$Al in AlPO$sb4$-cristobalite). For AlPO$sb4$-cristobalite, a discontinuous increase of both the $sp{31}$P and $sp{27}$Al relaxation rates at the $alpha-beta$ transition and a logarithmic divergence of the $sp{27}$Al relaxation rates in the $beta$ phase support a dynamical order-disorder model for this transition. On the other hand, the lack of such an increase in the $sp{29}$Si relaxation rates in anorthite across the P1-I1 transition support the conclusion that this transition is displacive.
Volume 39 of Reviews in Mineralogy and Geochemistry about Transformation Processes in Minerals summarises the current state of the art. The selection of transformation processes covered here is by no means comprehensive, but represents a coherent view of some of the most important processes which occur specifically in minerals. Contents: Rigid unit modes in framework structures Strain and elasticity at structural phase transitions in minerals Mesoscopic twin patterns in ferroelastic and co-elastic minerals High-pressure structural phase transitions Order-disorder phase transitions Phase transformations induced by solid solution Magnetic transitions in minerals NMR spectroscopy of phase transitions in minerals Insights into phase transformations from Mössbauer spectroscopy Hard mode spectroscopy of phase transitions Synchrotron studies of phase transformations Radiation-induced amorphization
All existing introductory reviews of mineralogy are written accord ing to the same algorithm, sometimes called the "Dana System of Mineralogy". Even modern advanced handbooks, which are cer tainly necessary, include basic data on minerals and are essentially descriptive. When basic information on the chemistry, structure, optical and physical properties, distinguished features and para genesis of 200-400 minerals is presented, then there is practically no further space available to include new ideas and concepts based on recent mineral studies. A possible solution to this dilemma would be to present a book beginning where introductory textbooks end for those already famil iar with the elementary concepts. Such a volume would be tailored to specialists in all fields of science and industry, interested in the most recent results in mineralogy. This approach may be called Advanced Mineralogy. Here, an attempt has been made to survey the current possibilities and aims in mineral matter investigations, including the main characteristics of all the methods, the most important problems and topics of mineral ogy, and related studies. The individual volumes are composed of short, condensed chap ters. Each chapter presents in a complete, albeit condensed, form specific problems, methods, theories, and directions of investigations, and estimates their importance and strategic position in science and industry.
30% discount for members of The Mineralogical Society of Britain and Ireland This volume addresses the fundamental factors that underlie our understanding of mineral behaviour and crystal chemistry - a timely topic given current advances in research into the complex behaviour of solids and supercomputing.
The structural and the magnetic properties of CeCu6-xAgx (0 ≤ x ≤ 0.85) and CeCu6-xPdx (0 ≤ x ≤ 0.4) have been studied using neutron diffraction, resonant ultrasound spectroscopy (RUS), x-ray diffraction measurements, and first principles calculations. The structural and magnetic phase diagrams of CeCu6-xAgx and CeCu6-xPdx as a function of Ag/Pd composition are reported. The end member, CeCu6, undergoes a structural phase transition from an orthorhombic (Pnma) to a monoclinic (P21/c) phase at 240 K. In CeCu6-xAgx, the structural phase transition temperature (Ts) decreases linearly with Ag concentration and extrapolates to zero at xS ≈ 0.1. The structural transition in CeCu6-xPdx remains unperturbed with Pd substitution within the range of our study. The lattice constant b slightly decreases with Ag/Pd doping, whereas a and c increase with an overall increase in the unit cell volume. Both systems, CeCu6-xAgx and CeCu6-xPdx, exhibit a magnetic quantum critical point (QCP), at x ≈ 0.2 and x ≈ 0.05, respectively. Near the QCP, long range antiferromagnetic ordering takes place at an incommensurate wave vector ([delta]1 0 [delta]2), where [delta]1 ~ 0.62, [delta]2 ~ 0.25, x = 0.125 for CeCu6-xPdx and [delta]1 ~ 0.64, [delta]2 ~ 0.3, x = 0.3 for CeCu6-xAgx. As a result, the magnetic structure consists of an amplitude modulation of the Ce moments which are aligned along the c axis of the orthorhombic unit cell.
Neutron Applications in Earth, Energy and Environmental Sciences offers a comprehensive overview of the wide ranging applications of neutron scattering techniques to elucidate the fundamental materials properties at the nano-, micro- and meso-scale, which underpin research in the related fields of Earth, Energy and Environmental Sciences. Introductions to neutron scattering fundamentals and instrumentation are paired with a thorough review of the applications to a large variety of scientific and technological problems, written through the direct experience of leading scientists in each field. Tailored to a wide audience, this volume provides the novice with an inspiring introduction and stimulates the expert to consider these non-conventional problem solving techniques in his/her field of interest. Earth and environmental scientists, engineers, researchers and graduate students involved with materials science will find Neutron Applications in Earth, Energy and Environmental Sciences a valuable ready-to-use reference.
This textbook describes the fundamental principles of structural phase transitions in materials in an easily understandable form, suitable for both undergraduate and graduate students.
