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On the basis of geophysical observations, cosmochemical constraints, and high-pressure experimental data, the Earth's liquid outer core consists of mainly liquid iron alloyed with about ten per cent (by weight) of light elements. Although the concentrations of the light elements are small, they nevertheless affect the Earth's core: its rate of cooling, the growth of the inner core, the dynamics of core convection, and the evolution of the geodynamo. Several light elements-including sulphur, oxygen, silicon, carbon and hydrogen-have been suggested, but the precise identity of the light elements in the Earth's core is still unclear. Oxygen has been proposed as a major light element in the core on the basis of cosmochemical arguments and chemical reactions during accretion. Its presence in the core has direct implications for Earth accretion conditions of oxidation state, pressure and temperature. Here we report new shockwave data in the Fe-S-O system that are directly applicable to the outer core. The data include both density and sound velocity measurements, which we compare with the observed density and velocity profiles of the liquid outer core. The results show that we can rule out oxygen as a major light element in the liquid outer core because adding oxygen into liquid iron would not reproduce simultaneously the observed density and sound velocity profiles of the outer core. An oxygen-depleted core would imply a more reduced environment during early Earth accretion.

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Near-UV-pumped white-light-emitting diodes with ultra-high color rendering and decreased blue-light emission is highly desirable.H owever,d iscovering as ingle-phase white light emitter with such characteristics remains challenging. Herein, we demonstrate that Mn doping as lowa s0 .027 %i n the hybrid post-perovskite type (TDMP)PbBr 4 (TDMP = trans-2,5-dimethylpiperaziniium) enables to achieve ab right pure white emission replicating the spectrum of the sunsrays. Thus,awhite phosphor exhibiting an emission with CIE coordinates (0.330, 0.365), ahigh photoluminescence quantum yield of 60 %( new recordf or white light emission of hybrid lead halides), and an ultra-high color rendering index (CRI = 96, R9 = 91.8), corresponding to the recordv alue for as ingle phase emitter was obtained. The investigation of the photoluminescence properties revealed how free excitons,s elftrapped excitons,and lowamount of Mn dopants are coupled to give rise to such pure white emission.Supportinginformation and the ORCID identification number(s) for the author(s) of this article can be found under: https://doi.