Crystal Structures and Electronic Properties of Xe–Cl Compounds at High Pressure

Abstract

Crystal structure prediction techniques coupled with enthalpies obtained at 0 K from density functional theory calculations suggest that pressure can be used to stabilize the chlorides of xenon. In particular, XeCl and XeCl 2 were calculated to become metastable by 10 GPa and thermodynamically stable with respect to the elemental phases by 60 GPa. Whereas at low pressures Cl 2 dimers were found in the stable phases, zigzag Cl chains were present in Cmcm XeCl at 60 GPa and atomistic chlorine comprised P6 3 /mmc XeCl and Fd3̅ m XeCl 2 at 100 GPa. A XeCl 4 phase that was metastable at 100 GPa contained monomers, dimers, and trimers of chlorine. XeCl, XeCl 2 , and XeCl 4 were metallic at 100 GPa, and at this pressure they were predicted to be superconducting below 9.0, 4.3, and 0.3 K, respectively. Spectroscopic properties of the predicted phases are presented to aid in their eventual characterization, should they ever be synthesized.

The XtalOpt Evolutionary Algorithm for Crystal Structure Prediction

“…With this in mind, currently the XtalOpt EA has successfully been employed to predict the structures of a number of atomistic inorganic crystals; a few recent examples can be found in refs − . Our group has mostly applied XtalOpt to study hydrides under conditions of extreme pressures, ,− because they have the potential to behave as conventional (Bardeen-Cooper-Schrieffer) high-temperature superconductors. , This line of reasoning can be traced back to Ashcroft, who pointed out that hydrogen and hydrogen-dominant alloys could have all of the properties required for conventional high-temperature superconductivity (large electron–phonon coupling, high density of states at the Fermi level, wide bands, and high vibrational frequencies).…”

The influence of electronegativity on linear and triangular three-centre bonds

“…The difluorides of Kr, Xe and Ra have been characterised as solids. 22 High pressure conditions have also been proposed for stabilisation of XeCl 2 23 and XeBr 2 21 but the low Δ XY values (Table 2, Entry 6) suggest low stability relative to the elements. Xenon dichloride may be accessible/detectable under carefully controlled conditions (gas phase, matrix isolation).…”

A First-Principles Exploration of NaxSy Binary Phases at 1 atm and Under Pressure

“…Because dispersion interactions are unlikely to be important under pressure [85], calculations at 100, 150 and 200 GPa were carried out with the PBE functional. Figure 1 illustrates that only Na 3 S and Na 2 S were thermodynamically stable at all of these pressures.…”

“…The pressure induced polymerization and bond weakening observed in the two-dimensional sulfur layers has been seen in other systems before. For example, it has been shown that the Cl 2 molecules present in XeCl at 40 GPa undergo polymerization to form one-dimensional zigzag chains by 60 GPa with the -iCOHPs between nearest neighbor atoms computed to be 3.81 eV and 2.16 eV, respectively [85]. By 100 GPa, however, there is no evidence of Cl-Cl bond formation with computed ELF and -iCOHPs characteristic for monoatomic Cl.…”