Melting experiments require rapid data acquisition due to instabilities of the molten sample and optical drifting due to the high required laser power. In this work, the melting curve of zirconium has been determined for the first time up to 80 GPa and 4000 K using in-situ fast x-ray diffraction (XRD) in a laser-heated diamond anvil cell (LH-DAC). The main method used for melt detection was the direct observance of liquid diffuse scattering (LDS) in the XRD patterns and it has been proven to be a reliable melting diagnostic. The effectiveness of other melting criteria such as the appearance of temperature plateaus with increasing laser power is also discussed. PACS numbers: 92.60.hv, 61.50.Ks, 74.62.Fj, 81.30.Bx Zirconium (Zr) and its alloys have a very wide range of applications, from the chemical processing (as corrosion resistant materials) to the semiconductor industry 1 . Moreover, its good strength and ductility at high temperatures and the low thermal neutron cross-section absorption make it an ideal material for use as cladding at nuclear reactors 2 . Alloys of Zr with Cu, Al, Ti and Ni have been demonstrated to exhibit extraordinary glass forming ability 3 , while metallic glass formation in singleelement zirconium has also been discovered, with a wide stability in high pressure and temperature conditions 4 .Zirconium is a d-orbital transition metal with a rich and interesting phase diagram. At ambient conditions it crystallizes to an hcp structure (α-phase), while at temperatures higher than 1136 K it transforms to a bcc (β-) phase. By increasing pressure at ambient temperature it transforms to another hexagonal, but not close-packed, called the ω-phase and then back to β-phase around 35 GPa 5-7 . Similar transitions also occur in other group IV transition metals, such as Ti and Hf, and it seems that the electronic transfer between the broad sp band and the much narrower d band is the driving force behind those structural transitions.The high melting point (2128 K) of Zr often classifies it as a refractory metal. Although there are some works in the high temperature behavior of zirconium at high pressures 8-11 , its melting curve has not yet been investigated and this absence of experimental data has strongly motivated this study. On the other hand, the high pressure melting of transition metals has always been a subject of intense debate, because of the large uncertainties in the temperature measurements and the criteria used to identify the melting, so that different approaches can yield very different results. In most cases shock wave (SW) experiments and molecular dynamics (MD) calculations provide dramatically steeper curves than those obtained with the laser speckle method in a LH-DAC, where the melting is visually detected by observing the movements on the sample surface during heating. Tantalum is a good example of such a controversy, with melt-ing temperatures that differ thousands of K at 100 GPa by applying different experimental techniques [12][13][14][15] . Another more recent example is...

An extended series of MIL‐53(M)_X metal–organic frameworks (MIL = Materials of Institute Lavoisier; M = Al, Cr, Fe, Sc; X = Cl, CH3, NO2) have been systematically investiaged to explore the impact of the nature of both the metal centre and the functions grafted on to the organic linker on the mechanical behaviour of this family of highly flexible hybrid porous frameworks under the application of an external pressure of up to 3 GPa. The high‐pressure X‐ray diffraction measurements allowed the characterization of the pressure‐induced phase transitions of the hydrated structures, the associated volume changes/pressure transitions, and their mechanical resilience through the determination of their bulk moduli.

We report boron isotope effect on the E 2g phonon mode by micro-Raman spectroscopy on the ternary Mg 1−x Al x B 2 system, synthesized with pure isotopes 10 B and 11 B. The isotope coefficient on the E 2g mode frequency is nearly 0.5 in the wide range of Al, with a tendency to decrease at MgB 2 ͑x =0͒. The intraband electron-phonon ͑e-ph͒ coupling relative to the sigma band has been extracted from the E 2g line-shape parameters. By tuning the Fermi energy near the electronic topological transition ͑ETT͒, where the sigma Fermi surface changes from two-dimensional to three-dimensional topology ͑in range 0 Ͻ x Ͻ 0.28͒, the E 2g mode shows the Kohn anomaly accompanied with a splitting into a hard and a soft component. The results suggest that the intraband hardly plays any role to control the high T c of Mg 1−x Al x B 2 The common physical features of diborides with the multigap FeAs-based superconductors and cuprates are discussed.

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We investigated the atomic structure of liquid Rb along an isothermal path at 573 K, up to 23 GPa, by X-ray diffraction measurements. By raising the pressure, we observed a liquid-liquid transformation from a simple metallic liquid to a complex one. The transition occurs at 7.5 ± 1 GPa which is slightly above the first maximum of the T-P melting line. This transformation is traced back to the density-induced hybridization of highest electronic orbitals leading to the accumulation of valence electrons between Rb atoms and to the formation of interstitial atomic shells, a behavior that Rb shares with Cs and is likely to be common to all alkali metals.