Computational Investigation of Electron Small Polarons in α-MoO3

The properties of electron small polarons in α-MoO3 are investigated computationally employing density-functional-theory with Hubbard-U corrections (DFT+U) and hybrid functionals (HSE06). These methods are used to compute the electronic and atomic structures of polarons localized on Mo ions, the barrier for adiabatic polaron hopping, and the magnitude of the binding energy with intercalated Li ions. The calculations establish a pronounced anisotropy in polaron mobilities, both within the bilayer sheets and across the van der Waals (vdW) gaps characteristic of the α-MoO3 structure. The lowest and highest energy barriers are found for hopping within the same bilayer plane and across the vdW gap, respectively. The binding energies between polarons and intercalated Li ions are calculated in supercells with composition Li0.028MoO3, yielding values of approximately 0.3 eV when Li ions are located in the one-dimensional channels within the bilayer sheets, and values that are approximately 0.1 eV lower in magnitude when Li resides in the two-dimensional interlayer van der Waals gaps.