Abstract
The high-pressure and high-temperature structural and chemical stability of ruthenium has been investigated via synchrotron X-ray diffraction using a resistively heated diamond anvil cell. In the present experiment, ruthenium remains stable in the hcp phase up to 150 GPa and 960 K. The thermal equation of state has been determined based upon the data collected following four different isotherms. A quasi-hydrostatic equation of state at ambient temperature has also been characterized up to 150 GPa. The measured equation of state and structural parameters have been compared to the results of ab initio simulations performed with several exchange-correlation functionals. The agreement between theory and experiments is generally quite good. Phonon calculations were also carried out to show that hcp ruthenium is not only structurally but also dynamically stable up to extreme pressures. These calculations also allow the pressure dependence of the Raman-active E2g mode and the silent B1g mode of Ru to be determined.
Highlights
Transition metals have always attracted the interest of the scientific community due to their unusual electronic and structural properties, originating from the dominant influence of their d electrons
In contrast with the results reported by Cynn et al, conclusions extracted from studies on iron-ruthenium alloys under high pressure suggest that a hcp-fcc transition should be expected in the range of the tenths of GPa23
In this work the stuctural and chemical evolution of Ru has been studied under HP-HT conditions combining angular dispersive (AD)-XRD and diamond anvil cell (DAC) techniques
Summary
Transition metals have always attracted the interest of the scientific community due to their unusual electronic and structural properties, originating from the dominant influence of their d electrons Often, they exhibit pronounced phonon anomalies as a result of complex Fermi-surface geometries coupled with strong electron-phonon interactions[1,2]. They exhibit pronounced phonon anomalies as a result of complex Fermi-surface geometries coupled with strong electron-phonon interactions[1,2] For these reasons, in the past decades big effort has been devoted to map and interpret the systematic properties of this metals at both ambient and extreme conditions of pressure and temperature[3]. Ru is inert to most chemicals and it is generally used in wear-resistant electrical contacts and thick-film resistors[4,5,6] It is often used alloyed with Pt and Pd as it increases their hardness. The experiments have been combined with first-principle calculations of the structural and lattice dynamic properties
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