|About this Abstract
||Materials Science & Technology 2020
||Materials vs Minerals: Bridging the Gap between Materials Science and Earth and Planetary Science
||Thermodynamic Modeling of Al-Ti-rich Pyroxene Solid Solutions: Deducing the Nebular Conditions of Condensation of Ti+3 and Ti+4 Oxidation States
||Venkateswara Manga, Tom Zega
|On-Site Speaker (Planned)
Calcium-aluminium-rich inclusions (CAIs) are radiometrically age-dated to 4.567 billion years and contain refractory mineral-solutions that formed at very high temperatures. The crystal chemistry of these constituent minerals in the inclusions offer clues to the thermodynamic landscape of the early solar nebula. One such important phase in the CAIs is the pyroxene, which exhibits a family of solid solutions with a monoclinic structure. In this talk we present first-principles-driven thermodynamic modeling of the Al-Ti-rich pyroxenes within the ternary space of CaTiAl2O6-CaTiAlSiO6-CaMgSi2O6. Thermochemical data predicted from the first-principles calculations of special-quasi-random structures of Ca(Ti+3,Mg+2,Ti+4)(Al+3,Si+4)O6 solid solutions is employed in the thermodynamic modeling of the phase within CALPHAD framework. The miscibility-gap exhibited by the pyroxene and the condensation temperature of the Al-Ti-rich and Mg-Si-rich endmembers are predicted under the nebular conditions. We discuss the thermodynamic conditions of occurrence of Ti+3 and Ti+4 oxidation states and the revised condensation temperatures of various refractory minerals.