Work

High-Pressure Synthesis and Characterization of the Novel Potassium Superhydride KH 9

Year: 2025

Type: article

Abstract: Through high-pressure diamond anvil cell experiments, we report the synthesis of two novel potassium superhydrides (KH 9 -I and KH 9 -II) and investigate their structural and vibrational properties via synchrotron X-ray powder diffraction and Raman spectroscopy, complemented by density functional theory (DFT) calculations. Above 17 GPa at room temperature, KH-II and H 2 react to form KH 9 -I; this reaction can be accelerated with temperature. KH 9 -I possesses a face-centered-cubic ( fcc ) potassium sublattice with a slight rhombohedral distortion (space group R 3̅ m ). Compression above 78 GPa converts KH 9 -I to another polymorph, KH 9 -II, which adopts a primitive simple hexagonal potassium sublattice (space group P 6/ mmm ) and remains stable up to at least 100 GPa. Both KH 9 polymorphs exhibit ionic character, comprising K + and H – ions, along with quasi-molecular H 2 units, resulting in rich Raman activity.

Source: The Journal of Physical Chemistry Letters

DOI: 10.1021/acs.jpclett.5c02024