ALBERT

Description / Table of Contents: The purpose of this short course is to examine the relations among the microscopic structure of minerals and their macroscopic thermodynamic properties. Understanding the micro-to-macro relations provides a rigorous theoretical foundation for formulation of energy relations. With such a foundation, measured parameters can be understood, and extrapolation and prediction of thermodynamic properties beyond the range of measurement can be done with more confidence than if only empirical relations are used. Mineral systems are sufficiently complex in structure and properties that a balance must be sought between rigorous complexity and useless simplicity. Eventually, even the most rigorous thermodynamic analysis requires simplifying assumptions in order to be tractable for complex minerals, and a firm foundation in the microscopic fundamentals should underlie those assumptions. The most fundamental questions of mineral physics and chemistry are "What minerals exist under given constraints of pressure, temperature, and composition, and why?" The macroscopic thermodynamic parameter defining mineral stability at a given pressure and temperature is the Gibbs free energy. The purpose of this course is to consider the microscopic factors that influence the free energy of minerals: atomic environments, bonding, and crystal structure. These factors influence the structural energy and the detailed nature of the lattice vibrations which are an important source of entropy and enthalpy at temperatures greater than 0 K. The same factors determine the relative energy of different phases, and thereby; the relative stability of different minerals. Configurational entropy terms arising from disorder also contribute to the energy and entropy. In transition metal compounds there are additional energy and entropy terms arising from the electronic configurations, leading to additional stabilizations, magnetic ordering, and, incidentally, color. Organized by Sue Kieffer and Alex Navrotsky, the course was presented by the ten authors of this book on the campus of Washington College in Chestertown, Maryland. This was the second of MSA's short courses to be given in conjunction with meetings of the American Geophysical Union.

Description / Table of Contents: This volume was prepared in conjunction with a short course, "Nanoparticles in the Environment and Technology," convened on the campus of the University of California, Davis, CA on December 8 and 9, 2001. Over the years, volumes in this series have taken a variety of forms. Many have focused on mature fields of investigation to draw together a comprehensive body of work and provide a definitive, up to date reference. A few, however, have sought to provide enough coverage of an emerging or re-emerging field to allow the reader to identify important and exciting gaps in current knowledge and opportunities for new research. This volume falls into the later category. Our primary goal in convening the short course and assembling this text is to invigorate future research. Early Reviews in Mineralogy dealt with specific groups of minerals, one (or two) volumes at a time. In contrast, this volume deals explicitly with the topic of crystal size in many different systems. Until recently, the special and complicated nature of the very smallest particles rendered them nearly impossible to study by conventional methods. Even today, the challenges associated with evaluating the size-dependence of a mineral's bulk and surface structures, properties, and reactivity are significant. However, ongoing improvements in sophisticated characterization, theory, and data analysis make particles previously described (often inaccurately) as "amorphous" (or even more mysteriously as "X-ray amorphous") amenable to quantitative evaluation. Thermochemical, crystal chemical, and computational chemical approaches must be combined to understand particles with diameters of 1 to 100 nanometers. Determination of the variation of structure, properties, and reaction kinetics with crystal size requires careful synthesis of size- and perhaps morphology-specific samples. These problems demand integration of mineralogical and geochemical approaches. Thus, it is appropriate that the current issue belongs to the era of Reviews in Mineralogy and Geochemistry. Nanoparticles and the Environment targets naturally occurring, finely particulate minerals, many of which form at low temperature. Thus, many of the compounds of interest are those of the "clay fraction". Of course, there have been decades of critical work on the structures, microstructures, and reactivity of finely crystalline or amorphous minerals, especially oxides, oxyhydroxides, hydroxides, and clays. We will not summarize what is known in general about these (for this, the reader is referred to earlier Reviews in Mineralogy volumes). Rather, our goal is to focus on the features of these materials that stem directly or indirectly from their size. The term "nanoparticles" is much more than a re-labeling designed to align "clay" (sized) minerals with nanotechnology and its goals. The term signifies that the substance has physical dimensions that are small enough to ensure that the structure and/or properties and/or reactivity are measurably particle size dependent, yet the particle is large enough to warrant its distinction from aqueous ions, complexes, or clusters. The chemistry, physics, and geology of particles at this intermediate scale are unique, fascinating, and important. Of particular interest are those properties that emerge only after a cluster of atoms has grown beyond some specific size, and disappear once the particle passes out of the "nanoparticle" size regime. There are some compelling examples of size-dependent phenomena. It is well known that the melting temperature of nanocrystals (defined as crystals having properties intermediate between molecular and crystalline) decreases dramatically as the radius of the cluster decreases. Absorption and luminescence spectra for small crystals are determined by the quantum-size effect. Decreasing nanocrystal size correlates with increased total energy of band edge optical transitions. As a consequence, the color of some nanocrystals correlates strongly with their particle size. Current world-wide interest in "nanotechnology" and "nanomaterials" offers a unique opportunity for the Earth sciences. Both the level of visibility and the explosion of synthesis and characterization techniques in physics, chemistry, and materials science provide mineralogy and geochemistry with new opportunities. It is important for us to show that the "nano" field consists of more than micromachines and electronic devices, and that nanoscale phenomena permeate and often control natural processes. Why all the fuss about nanoparticles now? As increasing attention in engineering is focused on making smaller and smaller machines, questions about the fundamental processes that govern nanoparticle form, stability, and reactivity emerge. The geoscience community is well equipped to tackle the basic science concepts associated with these questions. However, we have our own reasons to study size-dependent phenomena. Size-dependent structure and properties of Earth materials impact the geological processes they participate in. This topic has not been fully explored to date. Chapters in this volume contain descriptions of the inorganic and biological processes by which nanoparticles form, information about the distribution of nanoparticles in the atmosphere, aqueous environments, and soils, discussion of the impact of size on nanoparticle structure, thermodynamics, and reaction kinetics, consideration of the nature of the smallest nanoparticles and molecular clusters, pathways for crystal growth and colloid formation, analysis of the size-dependence of phase stability and magnetic properties, and descriptions of methods for the study of nanoparticles. These questions are explored through both theoretical and experimental approaches. Nanoparticles participate in every crystallization reaction and they constitute a major source of surface area in environments where virtually every important reaction takes place on a surface. They are components of enzymes and key biomolecules and their presence may record the early existence of life. How can we not be fascinated by these remarkable, and special, forms of matter?

Description / Table of Contents: Over the years, volumes in this series have taken a variety of forms. Many have focused on mature fields of investigation to draw together a comprehensive body of work and provide a definitive, up to date reference. A few, however, have sought to provide enough coverage of an emerging or re-emerging field to allow the reader to identify important and exciting gaps in current knowledge and opportunities for new research. This volume falls into the later category. Our primary goal in convening the short course and assembling this text it is to invigorate future research. Early “Reviews in Mineralogy” dealt with specific groups of minerals, one (or two) volumes at a time. In contrast, this volume deals explicitly with the topic of crystal size in many different systems. Until recently, the special and complicated nature of the very smallest particles rendered them nearly impossible to study by conventional methods. Even today, the challenges associated with evaluating the size-dependence of a mineral’s bulk and surface structures, properties, and reactivity are significant. However, ongoing improvements in sophisticated characterization, theory, and data analysis make particles previously described (often inaccurately) as “amorphous” (or even more mysteriously as “x-ray amorphous”) amenable to quantitative evaluation. Thermochemical, crystal chemical, and computational chemical approaches must be combined to understand particles with diameters of 1 to 100 nanometers. Determination of …

Description / Table of Contents: Global climate change with substantial global warming may be the most important environmental challenge facing the world. Geologic carbon sequestration (GCS), in concert with energy conservation, increased efficiency in electric power generation and utilization, increased use of lower carbon intensity fuels, and increased use of nuclear energy and renewable sources, is now considered necessary to stabilize atmospheric levels of greenhouse gases and global temperatures at values that would not severely impact economic growth and the quality of life on Earth. Geological formations, such as depleted oil and gas fields, unmineable coal beds, and brine aquifers, are likely to provide the first large-scale opportunity for concentrated sequestration of CO2. The specific scientific issues that underlie subsurface sequestration technology involve the effects of fluid flow combined with chemical, thermal, mechanical and biological interactions between fluids and surrounding geologic formations. Complex and coupled interactions occur both rapidly as the stored material is emplaced underground, and gradually over hundreds to thousands of years. The long sequestration times needed for effective storage, the large scale of GCS globally necessary to significantly impact atmospheric CO2 levels, and the intrinsic spatial variability of subsurface formations provide challenges to both scientists and engineers. A fundamental understanding of mineralogical and geochemical processes is integral to the success of GCS. Large scale injection experiments will be carried out and monitored in the next decade provides a unique opportunity to test our knowledge of fundamental hydrogeology, geochemistry and geomechanics.