Structure, chemistry, and properties of mineral nanoparticles

STRUCTURE, CHEMISTRY AND PROPERTIES OF MINERAL NANOPARTICLES Glenn Waychunas 1 , Hengzong Zhang 2 and Ben Gilbert 1 Lawrence Berkeley National Laboratory University of California, Berkeley Nanoparticle properties can depart markedly from their bulk analog materials, including large differences in chemical reactivity, molecular and electronic structure, and mechanical behavior. The greatest changes are expected at the smallest sizes, e.g. 10 nm and below, where surface effects are expected to dominate bonding, shape and energy considerations. The precise chemistry at nanoparticle interfaces can have a profound effect on structure, phase transformations, strain, and reactivity. Certain phases may exist only as nanoparticles, requiring transformations in chemistry, stoichiometry and structure with evolution to larger sizes. In general, mineralogical nanoparticles have been little studied. WHAT’S REALLY DIFFERENT ABOUT NANOPARTICLES Nanoparticles, particularly those with diameters of less than 10 nm, have a high proportion of atoms near their surfaces (ca. 16% for a 10 nm cube). Because of this, several important aspects of surfaces can drive deviations from bulk structure and chemistry at different size scales. Size also directly affects a number of other bulk properties due to restriction on wave function radius, separation of defects and interacting strain fields, the relative overall dominance of bulk or surface energy, and changes in vibrational properties. Studies of nanoparticles connect with several other important scientific areas dealing with lower