Theoretical aspects in structural distortion and the electronic properties of lithium peroxide under high pressure

Abstract

The structural phase transition and electronic properties of Li2O2 under pressures up to 500 GPa have been investigated using first-principles calculations. Two new structural phase transitions have been proposed at pressures around 75 GPa from the P63/mmc structure to the P21 structure and around 136 GPa from the P21 structure to the P21/c structure. The calculated phonon spectra have confirmed the dynamical stability of these structures. The pressure dependence of the lattice dynamics, O-O bond length, and band gaps in Li2O2 have also been reported. The band gaps of the P63/mmc, P21, and P21/c structures calculated by PBE and HSE06 have shown increasing trends with increasing pressure. Interestingly, the P63/mmc band gap and c/a ratio have significantly decreased with the increasing O-O bond length and ELF value around 11 and 40 GPa. At these pressures, the phonon frequency of the O-O stretching modes has softened. This finding reveals the effects of structural distortion in three phases of Li2O2. Our study provides structural understanding and the electronic properties of Li2O2 under high pressure, which might be useful for investigating the charge transport through Li2O2 in lithium-air batteries and CO2 capture.

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

“…In addition, dramatic changes of ELF have also been predicted in the P6 3 /mmc structure of Li 2 O 2 at 11 and 40 GPa. 34 It was predicted that there is some charge transfer between the O and Li atoms at these pressures. However, the charge transfer may also occur in the Amm2 structure of Na 2 O 2 , but the marked change of the partial density of states of the Na and O atoms was not found in this work.…”

High-Pressure Structural Transformation Pathway and Electronic Properties of AgGaTe2: Ab Initio Evolutionary Structural Searching

“…For a few decades, high-pressure structural searching has been successful in both elemental solids − and compounds. , It paves the ways to solve some puzzles in high-pressure physics and design new materials, such as superhard materials, , high- T c superhydride materials, − and hydrogen storage materials . Therefore, the recent work aims at investigating the high-pressure phase transitions of AgGaTe 2 using ab initio evolutionary structural searching up to 100 GPa.…”

Structural phase transitions and electronic properties of LI2o2 and Na2o2 under high pressure for Co2 capture application

“…This result is in agreement with the collapses of the Li(1)-Li(2) and Li(2)-Li(2) distances during the P6 3 /mmc to P2 1 phase transition [Figure 18(c)], which relates to the alignment of the Li atoms in the P2 1 structure with respect to the sequence stacking of the Li atoms in the P6 3 /mmc structure. [67].…”

“…and (c and d) the P2 1 /c structure at 150 and 500 GPa, respectively. The dashed lines denote the Fermi level, which is set to zero [67]. The  p * antibonding and the  p * antibonding states of the O-O bonds in Li 2 O 2 are represented by the conduction band and the valence band states with almost no contribution from the Li states [72,73].…”

“…: The vibrational modes, activities in the IR and Raman spectra for the P-62m and the Amm2 structures at 0 GPa, the P2 1 /c structure at 22 GPa, and the Pbam structure at 30 GPa [76] Figure 14: (a) Plot of the enthalpy differences of the various structures compared to the P2 1 /c structure predicted by Deng et al [16] (denoted as P2 1 /c † hereafter) versus pressure at 0-500 GPa, (b) Plot of the enthalpy difference of the P2 1 structure compared to the P2 1 /c structure in the pressure range of 50-150 GPa [67]. ................ 41 Figure 31: Simulated XRD patterns of the crystal structures: (a) Na 2 O 2 -II at 550C and ambient pressure calculated from the Tallman's experimental data [20], and (b)-(c) are the I4/mmm and the P4/mbm structures at 0 K and ambient pressure obtained from the AIRSS searches [76] Figure 32: Simulated XRD patterns of the crystal structures: (a) Na 2 O 2 -Q at room temperature and ambient pressure calculated from the Tallman's experimental data [20], and (b)-(d) are the Pmmm, the Immm, and the C2/m structures at 0 K and ambient pressure obtained from the AIRSS searches, respectively [76].…”