A new orthorhombic high pressure phase was observed in CsH at approximately 17.5 GPa and V/Vp = 0.53. This high pressure phase was assigned to the CrB structure with the Cmcm space group based upon 19 x-ray diffraction peaks. It was studied to V/Vo = 0.260 at 253 GPa. This is the highest compression measured in the ionic alkali hydrides to date. At 253 GPa, the bulk modulus of CsH (881 GPa) is nearly double that of diamond at atmospheric pressure (442 GPa). PACS numbers: 62.50.+p, 61.10.Lx, 64.30.+t, 64.60.i In metallic hydrides the hydrogen particle forms both covalent and ionic bonds. At ambient pressure, transition metal hydrides have covalent bonding, whereas alkali metal hydrides are principally ionic [1]. The alkali halides are assumed to have a complete charge transfer of 1.0e between alkali anions and halide cations. By comparison, the alkali hydrides are computed to have a charge transfer of 0.73e [2]. While more covalent than the alkali halides, the alkali hydrides are crystallographically similar to the alkali halides and are expected to behave similarly with the increasing pressure.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.