Phase diagram of calcium at high pressure and high temperature

Resistively heated diamond-anvil cells have been used together with synchrotron x-ray diffraction to investigate the phase diagram of calcium up to 50 GPa and 800 K. The phase boundaries between the Ca-I (fcc), Ca-II (bcc), and Ca-III (simple cubic, sc) phases have been determined at these pressure-temperature conditions, and the ambient temperature equation of state has been generated. The equation of state parameters at ambient temperature have been determined from the experimental compression curve of the observed phases by using third-order Birch-Murnaghan and Vinet equations. A thermal equation of state was also determined for Ca-I and Ca-II by combining the room-temperature Birch-Murnaghan equation of state with a Berman-type thermal expansion model.Part of the research was supported by the Spanish Government MINECO under Grants No. MAT2016-75586-C4-1/4P and No. MAT2015-71070-REDC.Peer reviewe

Band Gap Closure, Incommensurability and Molecular Dissociation of Dense Chlorine

Molecular systems are predicted to transform into atomic solids and be metallic at high pressure; this was observed for the diatomic elements iodine and bromine. Here the authors access the higher pressures needed to observe the dissociation in chlorine, through an incommensurate phase, and provide evidence for metallization

ABSORB-7 and ABSORB-GUI for single-crystal absorption corrections

ABSORBis a program to calculate and apply absorption corrections to single-crystal X-ray intensity data from any source, any detector type and any instrument configuration. A new version,ABSORB-7, contains several significant new features.ABSORB-GUIhas been developed to allow much easier specification of standard experiments and to enable experimental information to be imported from diffractometer software. The program that calculates the absorption calculations has been reconfigured to allow it to be called directly from other commercial and non-commercial software packages. In addition, a number of new features have been introduced to allow more flexibility in the way the experimental configuration is described and to correct synchrotron diffraction data collected with beams smaller than the sample crystal.</jats:p

Integration of Direct Methods With Macromolecular Crystallographic Techniques

The role of direct methods in macromolecular crystallography is discussed. The common belief that such methods will still remain marginal is rejected. Different sectors are analyzed. A direct procedure for phasing reflections when diffraction data of one isomorphous derivative are available is briefly described. The applications to experimental data of some test structures succeeded, and suggest that direct methods are competitive with traditional SIR techniques. Attention is also devoted to a formula which is able to recover the total from a partial structure. Direct methods can play a central role also for expanding (and refining) phases from derivative to native resolution, and can constitute an alternative to traditional molecular replacement techniques. 1 Introduction The use of traditional direct methods for solving macromolecular crystal structures or for refining phases was initiated several years ago. It was soon realized that Sayre equation, tangent formula, Karle-Hauptman d..

EosFit7c and a Fortran module (library) for equation of state calculations

none3noneANGEL R.;Gonzalez-Platas J;Alvaro MAngel, ROSS JOHN; Gonzalez Platas, J; Alvaro, Matte

Humulene derivatives from Saharian Asteriscus graveolens

International audienc

Behavior of Yb3+ and Er3+ during Heat Treatment in Oxyfluoride Glass Ceramics

The effects of alumina content and heat treatment on upconversion properties of codoped (ErF3-YbF3) oxyfluoride glass ceramics were investigated. Results showed that alumina content had an effect on phase separation and viscosity of the glass. Due to the high viscosity of low alumina content glass, the phase separated areas were smaller in these specimens. Increasing the heat treatment temperature led to the incorporation of Er3+ ions into CaF2 crystals and also increased the Yb3+ concentration in them. This increase improved the energy transfer and back transfer process between Er3+ and Yb3+ ions and as result upconversion intensity was increased