Semiempirical (neglect of diatomic differential overlap, NDDO) molecular orbital (MO) calculations without local approximations are now possible for 100,000 atoms or more with the massively parallel EMPIRE program. Calculations on systems of this size or with periodic boundary conditions for repeat units up to 50,000 atoms make realistic nanoscale systems accessible to MO theory, even for flexible systems, for which thousands of snapshots need to be calculated.<br/>The importance of such calculations lies in the fact that we are no longer limited to small or homogeneous, perfect systems, but can now include defects, dopants, impurities or domain boundaries in the calculations, or even calculate amorphous systems.<br/>The results of such calculations can be used to search for conduction paths through devices or redox-active proteins or to simulate charge-transport through disordered monolayers. The figure shows the results of simulations of hole-transport through a self-assembled monolayer substituted with a p-type organic semiconductor and with crystalline domains.<br/>Very large-scale calculations can also be used to investigate size effects in nanoparticles or to construct large amorphous structures in order to construct, for instance, amorphous carbon nanodots. Amorphous nanoparticles can be cut out of these periodic structures with very large repeat units for studies of, for instance, their photophysics.<br/>

Approaching reality: Simulating electronic devices

254th National Meeting (2017)

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