Hot Enough to Melt Iron: Earth's core is divided into a fluid outer core and a solid inner core, both composed predominately of iron at extremely high pressures and temperatures. The boundary between these two regions is largely controlled by the melting point of iron at ∼330 GPa, which in turn influences heat transfer and geodynamo generation. Anzellini et al. (p. 464 , see the Perspective by Fei ) compressed iron in a laser-heated diamond anvil cell, tracking its structure and texture by using time-resolved x-ray diffraction as the pressure increased to 200 GPa. The melting curve suggests the possibility of high heat flux and partial melting at the core-mantle boundary.

The isothermal equation of state of rhenium has been measured by powder X-ray diffraction experiments up to 144 GPa at room temperature in a diamond anvil cell. A helium pressure transmitting medium was used to minimize the non-hydrostatic stress on the sample. The fit of pressure-volume data yields a bulk modulus K₀ = 352.6 GPa and a pressure derivative of the bulk modulus $K{\prime }_0=4.56$ . This equation of state differs significantly from a recent determination [Dubrovinsky et al., Nat. Commun. 3, 1163 (2012)], giving here a lower pressure at a given volume. The possibility of using rhenium gasket X-ray diffraction signal, with the present equation of state, to evaluate multi-Mbar pressures in the chamber of diamond anvil cells is discussed.

This study shows how a few nanometer-sized crystals markedly increase the viscosity of a magma leading to explosive eruptions.

We present an in-situ powder X-ray diffraction study on the phase stability and polymorphism of the metal-organic framework ZIF-4, Zn(Imidazolate)₂, at simultaneous high-pressure and high-temperature, up to 8 GPa and 600 °C. The resulting pressure-temperature phase diagram reveals four, previously unknown, high-pressure-temperature ZIF phases. The crystal structures of two new phases – ZIF-4-cp-II and ZIF-hPT-II – were solved by powder diffraction methods. The total energy of ZIF-4-cp-II was evaluated using density functional theory calculations and was found to lie in between that of ZIF-4 and the most thermodynamically stable polymorph, ZIF-zni. ZIF-hPT-II was found to possess a doubly-interpenetrated diamondoid-topology and is isostructural with previously reported Cd(Imidazolate)₂ and Hg(Imidazolate)₂ phases. This phase exhibited extreme resistance to both temperature and pressure. The other two new phases could be assigned with a unit cell and space group, though their structures remain unknown. The pressure-temperature phase diagram of ZIF-4 is strikingly complicated when compared with that of the previously investigated, closely related ZIF-62, and demonstrates the ability to traverse complex energy landscapes of metal-organic systems using the combined application of pressure and temperature.

In the past couple of decades, the laser-heated diamond anvil cell (combined with in situ techniques) has become an extensively used tool for studying pressure-temperature-induced evolution of various physical (and chemical) properties of materials. In this review, the general challenges associated with the use of the laser-heated diamond anvil cells are discussed together with the recent progress in the use of this tool combined with synchrotron X-ray diffraction and absorption spectroscopy.