Molten barium titanate: a high-pressure liquid silicate analogue

The structure of molten BaTiO3 has been measured using laser heating, aerodynamic levitation and a combination of neutron diffraction with Ti isotope substitution, x-ray diffraction and spectroscopy. All measurements indicate a Ti-O coordination of n(TiO) = 4.4(2), far lower than the perovskite or hexagonal crystalline forms. However, n(TiO) > 4 suggests structural analogy with molten silicates at high pressures. We introduce methodology for ascertaining such analogies and demonstrate similarity with molten CaSiO3 at upper mantle pressures circa 5 GPa. Although some topological differences exist, we propose that planetary melt analogues provide rich insight into important processes relevant to hot exoplanets and Earth's early history.