Isotope Fractionation in TiO2 Polymorphs (Rutile, Anatase, Brookite) Estimated from “First Principles”

Resumo

Temperature relations of β-factors for ¹⁸O/¹⁶O fractionations in TiO₂ polymorphs have been determined using the density functional theory:

1000 ln β_rt(¹⁸O/¹⁶O) = 6.93039x – 0.08158x² + 0.00116x³ + 0.08305*P

1000 ln β_ant(¹⁸O/¹⁶O) = 7.34275x – 0.09906x² + 0.00153x³ + 0.08027*P

1000 ln β_brk(¹⁸O/¹⁶O) = 7.19088x – 0.09157x² + 0.00139x³ + 0.07601*P,

x = 10⁶/T(K)², P is pressure (GPa). The deduced relations can be applied for isotope thermometry if combined with β-factors of coexisting phases.