New methods in quantitative transmission electron microscopy (TEM) will be employed to address problems in the geosciences. (1) Geometric phase analysis will be used to measure structural perturbations in minerals with unprecedented detail and accuracy. In the process, elastic constants applicable to highly strained, nanometer-sized regions will be determined. (2) Fluctuation electron microscopy will be used to determine the detailed structure of amorphous and near-amorphous (paracrystalline) materials, starting with carbon and then silicate glasses. (3) Studies of small-scale chemical and structural variations in selected minerals and mineral groups using high-resolution TEM and related techniques will continue.

The proposed work opens new research areas for the geosciences through the use of quantitative methods of electron microscopy. Geometric phase analysis, which combines HRTEM imaging and intensive image analysis, will result in (1) quantitative near-atomic-scale measurements of displacements and strain resulting from dislocations and grain boundaries; (2) measurements of the waviness of low-angle grain boundaries like that recently discovered in olivine; (3) determination of the spatially resolved strain-energy density near dislocation cores – regions that were previously inaccessible; and (4) measurement of the strain fields and energies of dissociated dislocations. Garnets and perovskites will be the first minerals studied. Results will be compared to calculations utilizing elastic theory. In the process, estimates of elastic constants for regions as close as one or two atomic spacings from crystallographic disruptions will be determined.

Through use of the new technique of fluctuation electron microscopy, the structures of amorphous and paracrystalline materials will be determined. Evidence of paracrystallinity will initially be examined in nominally amorphous carbon that shows no apparent crystallinity but contains intriguing irregularities when viewed using high-resolution TEM. Structural variations of samples showing paracrystallinity will be correlated with environmental variables. Fluctuation microscopy will also be used to study the order in emerging crystalline phases at the homogeneous nucleation stage of silicate glasses of geological interest. High-resolution imaging and electron diffraction will be use to study cation ordering on a highly local scale in garnet and layer silicates.