Effective model for the electronic properties of quasi-one-dimensional purple bronze Li0.9Mo6O17 based on ab initio calculations

We investigate the electronic structure of the strongly anisotropic, quasi-low-dimensional purple bronze Li0.9Mo6O17. Building on all-electron ab initio band-structure calculations, we obtain an effective model in terms of four maximally localized Wannier orbitals, which turn out to be far from atomiclike. We find two half-filled orbitals arranged in chains running along one crystallographic direction and two full orbitals in perpendicular directions, respectively. The possibility to reduce this model to only two orbitals forming two chains per unit cell with interchain coupling is discussed. Transport properties of these models show high anisotropy, reproducing trends of the experimentally determined values for the dc conductivity. We also consider basic effects of electron-electron interactions using the (extended) variational cluster approach and dynamical mean field theory. We find good agreement with experimental photoemission data upon adding moderate onsite interaction of the order of the bandwidth to the ab initio derived tight-binding Hamiltonian. The obtained models provide a profound basis for further investigations on low-energy Luttinger-liquid properties or to study electronic correlations within computational many-body theory.