Micro hydration structure of aqueous Li + by DFT and CPMD

Systematic study on microscopic hydration structure of lithium ion hydrated clusters, [Li(H 2 O) n ] + ( n = 1–20), was carried out by density functional theory (DFT) calculations at ω B97XD/6-311++G( d,p ) basis l evel and Car-Parrinello molecular dynamics. The DFT calculation results reveal that the four-coordinated structure is the favorable first hydration sphere for [Li(H 2 O) n ] + ( n = 1–20) clusters in the aqueous phase. The second hydration layer of Li + is 8 water molecules when n ≥ 12. The energy parameters calculation shows that the structures of the first and second hydration shells are relatively steady. For n > 9, the competitive effects of the second and third hydration layers on water molecules arise and the solvent-solvent interactions for outer hydration shell are strengthened. The results of bond parameters declare that the structure of inner hydration shell has little influence on the H 2 O molecules of outer hydration layer when the first and second hydration spheres of Li + are saturated. MD simulation results prove Li + has a strong first hydration shell with Li–O (I, W) distance of 1.970 Å. Around 8.66 water with Li–O (I, W) distance of 4.10 Å from the second hydration shell. Both DFT and CPMD show Li + possesses a second hydration shell which is dominantly surrounded by 8 water molecules. Graphical abstract