We measure the electrical resistivity of hcp iron up to ∼170  GPa and ∼3000  K using a four-probe van der Pauw method coupled with homogeneous flattop laser heating in a DAC, and compute its electrical and thermal conductivity by first-principles molecular dynamics including electron-phonon and electron-electron scattering. We find that the measured resistivity of hcp iron increases almost linearly with temperature, and is consistent with our computations. The results constrain the resistivity and thermal conductivity of hcp iron to ∼80±5  μΩ cm and ∼100±10  W m^{-1} K^{-1}, respectively, at conditions near the core-mantle boundary. Our results indicate an adiabatic heat flow of ∼10±1  TW out of the core, supporting a present-day geodynamo driven by thermal and compositional convection.

Polymorphism, which describes the occurrence of different lattice structures in a crystalline material, is a critical phenomenon in materials science and condensed matter physics. Recently, configuration disorder was compositionally engineered into single lattices, leading to the discovery of high-entropy alloys and high-entropy oxides. For these novel entropy-stabilized forms of crystalline matter with extremely high structural stability, is polymorphism still possible? Here by employing in situ high-pressure synchrotron radiation X-ray diffraction, we reveal a polymorphic transition from face-centred-cubic (fcc) structure to hexagonal-close-packing (hcp) structure in the prototype CoCrFeMnNi high-entropy alloy. The transition is irreversible, and our in situ high-temperature synchrotron radiation X-ray diffraction experiments at different pressures of the retained hcp high-entropy alloy reveal that the fcc phase is a stable polymorph at high temperatures, while the hcp structure is more thermodynamically favourable at lower temperatures. As pressure is increased, the critical temperature for the hcp-to-fcc transformation also rises.

α-Glycine is studied up to 50 GPa using synchrotron angle-dispersive X-ray powder diffraction (XRD), Raman spectroscopy, and quantum chemistry calculations performed at multiples levels of theory. Results from both XRD and Raman experiments reveal an extended pressure stability of the α phase up to 50 GPa and the room temperature (RT) equation of state (EOS) was determined up to this pressure. This extended stability is corroborated by density functional theory (DFT) based calculations using the USPEX evolutionary structural search algorithm. Two calculated EOSs, as determined by DFT at T = 0 K and semiempirical density functional tight-binding (DFTB) at RT, and the calculated Raman modes frequencies show a good agreement with the corresponding experimental results. Our work provides a definitive phase diagram and EOS for α-glycine up to 50 GPa, which informs prebiotic synthesis scenarios that can involve pressures well in excess of 10 GPa.