Ab initio investigation of the effect of pressure on the structure and electronic properties of alkali metal oxides and peroxides

Discovery of Rhombohedral NaIrO3 Polymorph by In Situ High-Pressure Synthesis of High-Oxidation-State Materials Using Laser Heating in Diamond Anvil Cells

“…26 Na 2 O 2 crystallizes in the hexagonal space group P6̅ 2m and shows no phase transitions up to 6.5 GPa. 27 NaCl has the cubic Fm3̅ m B1 phase at 6.5 GPa and is used as a pressure calibrant during the experiment. 24 NaClO 3 crystallizes in the cubic P2 1 3 space group at ambient pressure and has been reported to have a phase transition at 5.5 GPa but with a very slow transition time (around 7 days).…”

“…Iridium crystallizes in the cubic Fm 3̅ m space group, is very incompressible, and has no phase transitions up to 6.5 GPa . Na 2 O 2 crystallizes in the hexagonal space group P 6̅2 m and shows no phase transitions up to 6.5 GPa . NaCl has the cubic Fm 3̅ m B1 phase at 6.5 GPa and is used as a pressure calibrant during the experiment .…”

Theoretical predictions for low-temperature phases, softening of phonons and elastic stiffnesses, and electronic properties of sodium peroxide under high pressure

“…To quantify the effect of pressure on the elastic anisotropy of the crystal structures, the universal elastic anisotropy index (A U ) of the Amm2 and the P 62m structures were calculated using eqn (2). At ambient pressure, the A U of the Amm2 and P 62m structures were slightly different with values of 0.28 and 0.24, respectively (see Fig.…”

“…Sodium peroxide (Na 2 O 2 ) is of great interest because of its broad applications, for example as a bleaching agent, oxidizing agent, and in breathing apparatus. 1,2 Na 2 O 2 is also utilized as an oxygen source by capturing carbon dioxide to generate oxygen and sodium carbonate. 1 Moreover, Na 2 O 2 has attracted much attention in energy storage for Na-O 2 batteries due to its high energy density.…”

Computational modelling of inorganic solids

“…Aleinikova et al 52 investigated the pressure dependence of alkali metal oxides and peroxides using DFT and fitting to the Birch-Murnaghan equation of state. They find that the band gap increases with pressure particularly for K 2 O.…”