Ab Initio Study of Single-and Double-Electron Capture Processes in Collisions of He^(2+) Ions and Ne Atoms

The single-and double-electron capture(SEC, DEC) processes of He^(2+) ions colliding with Ne atoms are studied by utilizing the full quantum-mechanical molecular-orbital close-coupling method. Total and state-selective SEC and DEC cross sections are presented in the energy region of 2 eV/u to 20 keV/u. Results show that the dominant reaction channel is Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s) in the considered energy region due to strong couplings with the initial state Ne(2s^(2)2p^(6)^(1)S) + He^(2+) around the internuclear distance of 4.6 a.u. In our calculations, the SEC cross sections decrease initially and then increase whereby, the minimum point is around 0.38 keV/u with the increase of collision energies. After considering the effects of the electron translation factor(ETF), the SEC cross sections are increased by 15%–25% nearby the energy region of keV/u and agree better with the available results. The DEC cross sections are smaller than those of SEC because of the larger energy gaps and no strong couplings with the initial state. Due to the Demkov-type couplings between DEC channel Ne^(2+)(2s^(2)2p^(4)^(1)S) + He(1s^(2)) and the dominating SEC channel Ne^(+)(2s2p^(6) ^(2)S) + He^(+)(1s), the DEC cross sections increase with increasing impact energies. Good consistency can also be found between the present DEC and the experimental measurements in the overlapping energy region.

Influence of electron correlations on double-capture process in proton helium collisions

The first-order correct-boundary Coulomb–Born distorted-wave approximation is used to study the double-electron capture by protons from the ground-state helium atoms at intermediate and high impact energies. The differential double capture cross sections are obtained as a function of the projectile scattering angle and the total cross sections as a function of the impact energy. In the considered range of impact energy, our calculation shows that although the results are not so sensitive to the static inter-electronic correlations in the initial channel, the strong final-state correlations have a large effect on the magnitudes of the double capture cross sections. The calculated differential and integral cross sections are compared with their available experimental values. The comparison shows a good agreement between the present calculations and the measurements. The comparison of the integral cross sections shows that the present approach is compatible with other theories.

Breaking the energy density limit of Li NiO_(2):Li_(2)NiO_(3)or Li_(2)NiO_(2)?

The development of next-generation layered oxide cathodes for high-energy-density electrical vehicle Li-ion batteries(LIBs)is an urgent topic.The existing method is achieved by continuously increasing the Ni contents of Ni-based layered oxides,but it has been limited to LiNiO_(2).To break this limit and attain increased energy densities,a promising strategy,which involves the introduction of excess Li ions into transition metal(TM)layers to form Li-excess compounds Li_(2)MO_(3)(M is a TM cation),has attracted enormous interest recently.However,another strategy,which has been neglected in recent years,involves the insertion of an extra layer of Li ions between the TM and original Li layers to form Li_(2)MO_(2).In this study,typical reversible Li_(2)NiO_(3) and 1T-Li_(2)NiO_(2) were selected as two representative cathodes to break the limit of LiNiO_(2),thereby availing comprehensive comparison with LiNiO_(2) regarding their overall properties as cathodes from a theoretical perspective.Interestingly,dissimilar to the Ni^(3+)/Ni^(4+)monoelectron cationic redox associated with LiNiO_(2),a polaronic anionic redox reaction occurs in Li_(2)NiO_(3),while a reversible Ni^(2+)/Ni^(4+)double-electron redox reaction accompanied by insulator-metal transition occurs in Li_(2)NiO_(2).Owing to this double-electron cationic activity,Li_(2)NiO_(2) exhibits absolute advantages over the other two materials(LiNiO_(2) and Li_(2)NiO_(3))as cathodes for LIBs in terms of the capacity,energy density,electronic conductivity,and thermal stability,thus rendering it the most promising candidate for next-generation layered oxide cathodes with high energy densities to break the limit of LiNiO_(2).