| Abstract Scope |
Primitive meteorites contain abundant refractory mineral phases, some of which are radiometrically age dated to 4.5673 billion years old and represent the first solids formed in our solar system. Materials such as spinel and perovskite, MgAl2O4 and CaTiO3, respectively, are among such phases. Equilibrium thermodynamics makes predictions that they and other materials should form in our solar system, based on its bulk composition, in a very specific sequence. Using aberration-corrected scanning transmission electron microscopy, we have identified nanostructures at odds with predictions, which includes variations in solute chemistry, solute segregation, and twinned structures. We have employed density-functional theory, which can account for such variations, with thermodynamic modeling to evaluate the temperatures and pressures under which these and related phases form. We suggest that such an approach can open up parameter space that was heretofore difficult to access via experimental methods and will discuss our results at the meeting. |