The fragment molecular orbital method combined with density-functional tight-binding and periodic boundary conditions

The density-functional tight-binding (DFTB) formulation of the fragment molecular orbital method is combined with periodic boundary conditions. Long-range electrostatics and dispersion are evaluated Ewald summation technique. first analytic derivatives energy respect to atomic coordinates lattice parameters formulated. accuracy established in comparison numerical gradients DFTB without fragmentation. largest elementary cell this work has 1631 atoms. applied elucidate polarization, charge transfer, interactions solution.