Here we have combined topological analysis, density functional theory (DFT) modeling, operando neutron diffraction, and machine learning algorithms within the comparative analysis of the known widely LiNiO 2 (LNO) and LiNi 0.8 Co 0.15 Al 0.05 O 2 (NCA) cathode materials. Full configurational spaces of the mentioned materials during delithiation were set using the topological approach starting from the 2 × 2 × 1 supercell (12 formula units in total) of the LNO structure (space group R3̅ m). Several types of the DFT models were applied for the structural relaxation of entries of the LNO configurational space (87 configurations) demonstrating a strong dependence of the results of optimization on the initial structure guess (at the latter delithiation stages) and on the Hubbard correction application (for the whole range of delithiation). Within the computationally easiest model considered for LNO, subsequent modeling of the NCA configurational space (20760 configurations) results in structural changes of the model cell that are well-consistent (relative errors <1.5% with respect to the lattice parameter values) with data of operando neutron diffraction experiments during charge−discharge cycling. In the scope of the machine learning approach, topology of Li layers and relative disposition of Li and Al in NCA structure are found to be the most important descriptors during the energy balance estimations.
The crystal structure and magnetic ordering in Sr 3 YCo 4 O 10.5+␦ , ␦ = 0.02 and 0.26 compounds have been revisited in a detailed neutron diffraction study. The ordering is of G-type, with the magnetic Co moments being aligned along the c axis of the tetragonal cells. In contrast to the previous studies, we, however, find an important peculiarity of the magnetic structures in the title compounds, namely, the magnetic moment magnitudes are different in the layers containing Co ions with different oxygen coordination. Along with the modulation of the coordination type and charge state of Co ions along the c axis, the ordered magnetic moment magnitudes are varying concomitantly and thus the correlation between the charge and spin states of the Co ions has been directly observed.
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