Evidence for Fe-Si-O liquid immiscibility at deep Earth pressures.

Seismic observations suggest that the uppermost region of Earth's liquid outer core is buoyant, with slower velocities than the bulk outer core. One possible mechanism for the formation of a stably stratified layer is immiscibility in molten iron alloy systems, which has yet to be demonstrated at core pressures. We find immiscibility between liquid Fe-Si and Fe-Si-O persisting to at least 140 GPa through a combination of laser-heated diamond-anvil cell experiments and first-principles molecular dynamics simulations.

Colloidal Organohalide Perovskite Nanoplatelets Exhibiting Quantum Confinement.

We prepare colloidal nanoplatelets of methylammonium lead bromide (MAPbBr3) perovskite and compare the optical signatures of excitons in these two-dimensional systems to spherical perovskite nanocrystals and the corresponding bulk phase. We find that excitonic features that had previously been attributed to quantum confinement in MAPbBr3 nanocrystals are in fact a property of the bulk perovskite phase. Furthermore, we find that higher-energy absorption features originate from two-dimensional nanoplatelets, which are present in the nanocrystal reaction product.