High-pressure x-ray diffraction on potassium and rubidium up to 50 GPa

Abstract

The effect of pressure on structural properties of potassium and rubidium is studied with diamondanvil cells by energy-dispersive x-ray diffraction with synchrotron radiation at room temperature up to 50 GPa. The K III structure of potassium at pressures above 23 GPa is indexed by the use of a tetragonal-body-centered lattice (tI16) with 16 atoms in the unit cell. A new phase is found for rubidium above 46 GPa. Equation of state data for these heavy alkali metals are presented and compared with earlier data for cesium.

K2O2: The most stable oxide of K

“…We have used α-oxygen 9 in an antiferromagnetic configuration for the oxygen reference energy and nonmagnetic K in body-centered cubic structure for the K reference energy. 10 Using oxygen molecule instead as our reference energy did not change the qualitative trends. An 8 × 8 × 8 Monkhorst-Pack k-point mesh was used for the …”

Metal–silicate partitioning of cesium: Implications for core formation

“…At pressures above those that produce the transition, alkali metals may behave more like transition metals, which also have electrons in d orbitals, and display a drastically increased solubility in iron. The s fi d transition is also applicable to the other alkali elements, with the pressure of that transition lowering for increasing atomic number (Winzenick et al, 1994). The appearance of this effect at 26 GPa for K suggests that the same transition for Cs should be well within the reach of a diamond-anvil cell (DAC) apparatus.…”

Metallic high-pressure modifications of main group elements

“…At pressures above 20 GPa the stability range of a phase with a hitherto unknown structure begins. The atomic arrangement bears some structural similarity to that of Rb-IV as evidenced by earlier X-ray diffraction data [11].…”

“…At pressures around 46 GPa, the appearance of new lines in the diffraction diagram indicates the onset of another structural phase transition [11]. A pure sample of this high-pressure modification Rb-VI can be obtained by annealing the pressurized metal at approximately 50 GPa and 393 K for 12 h [17].…”