Correspondence: Reply to Strongly-driven Re+CO2 redox reaction at high-pressure and high-temperature

Santamaria-Perez et al. attempt to reproduce our CO2–SiO2 solid solution2. In their study, mixtures of CO2 and SiO2 similar to those studied in our work2 were indirectly laser heated up to 2,400K and 50 GPa by using Re as an internal heater, and a CO2–SiO2 solid solution was not obtained. Instead, the only temperature quenched crystalline phases identified by X-ray diffraction were: known polymorphs of pure CO2 and SiO2, Re and ReO2. In particular, the structure of ReO2 was identified as being the b-ReO2 (Pbcn), which is a well known phase of this oxide discovered many decades ago (ref. 9 in the letter). ReO2 was then inferred to form from a high P–T, ReþCO2 redox reaction. Moreover, it is shown that b-ReO2 may provide a better fit to our XRD pattern than the cristobalite-like CO2–SiO2 solid solution. A shadow is then cast on the very existence of this solid solution. In light of this study, we have reanalysed all our data, and realized that more complex chemical reactions may have occurred in our samples due to the extreme high temperatures: T>4,000 K.