  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 atomic
like. 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 inter-chain 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 photo emission data upon adding moderate on-site
interaction of the order of the band width 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.
