Insights into Li+ Migration Pathways in α-Li3VF6: A First-Principles Investigation

Magnetic, structural, and defect properties of lithium vanadium hexafluoride (alpha-Li3VF6) are investigated theoretically with periodic quantum chemical methods. It is found that the ferromagnetic phase is more stable than the antiferromagnetic phase. The crystal structure contains three inequivalent Li sites (Li(1), Li(2), and Li(3)), where Li(1) occupies the middle position of the triplet Li(2)-Li(1)-Li(3). The calculated Li vacancy formation energies show that vacancy formation is preferred for the Li(1) and Li(3) sites compared to the Li(2) position. The Li exchange processes between Li(1) <-> Li(3), Li(1) <-> Li(2), and Li(2) <-> Li(3) are studied by calculating the Li+ migration between these sites using the climbing-image nudged elastic band approach. It is observed that Li exchange in alpha-Li3VF6 may take place in the following order: Li(1) <-> Li(3) > (Li(1) <-> Li(2) > Li(2) <-> Li(3). This is in agreement with recently published results obtained from 1D and 2D Li-6 exchange nuclear magnetic resonance spectroscopy.