We establish a rigorous computational scheme for constructing an effective Hamiltonian to be used for the determination of the charge carrier mobility of pure organic crystals at finite temperature, which accounts for van der Waals interactions, and it includes vibrational contributions from the entire phonon spectrum of the crystal. Such an approach is based on the ab initio framework provided by density functional theory and the construction of a tight-binding effective model via Wannier transformation. The final Hamiltonian includes coupling of the electrons to the crystals phonons, which are also calculated from density functional theory. We apply this methodology to the case of durene, a small π-conjugated molecule, which forms a high-mobility herringbone-stacked crystal. We show that accounting correctly for dispersive forces is fundamental for obtaining a high-quality phonon spectrum, in agreement with experiments. Then, the mobility as a function of temperature is calculated along different crystallographic directions and the phonons most responsible for the scattering are identified.
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