Calcolo ab initio della massa effettiva e implementazione del codice CRYSTAL

Transport properties of materials have a paramount importance in many fields of material science and solid state physics such as the study of thermoelectric materials through its intimate relation with mobility. Among transport properties of materials, effective mass of electrons and holes may be considered as one of the simplest to be computed, even though one of the most interesting applicationwise. Although the definition of effective mass, in an harmonic band approximation seems quite simple, it turns out to be useful in many applications and the computational cost for evaluating it is small. In this thesis, two approaches: a semi-analytical and a numerical formulation for the effective mass are utilized. For calculations of wavefunctions Density Functional theory utilizing different functionals and Hartree Fock method are employed . The code is implemented in the public CRYSTAL code which has been under constant development for four decades. Subsequently, the code was tested in comparison with available literature for various material including several metal oxides and available numerical code (EMC). Although the results are not always in good agreement with experimental results as a consequence of simplifying assumptions, the results are numerically stable and with a good agreement with other codes.