We show a novel approach to QM/QM calculations within the framework of linear-scaling DFT as implemented in the ONETEP program. Direct energy minimization with respect to the density matrix is performed using localized, non-orthogonal functions to exploit near-sightedness of electronic matter. The aim of this project is to divide the molecular system into two regions of different level of resolution. In one region, the localized functions are optimized in-situ using a plane-wave basis set, whereas in the other they remain frozen during the calculation. The interactions at the interface of the regions are naturally described due to the optimization of the density matrix in the whole system. As a result, a large portion of computational effort is saved, allowing to perform calculations on large systems of thousands of atoms while keeping chemical accuracy. The tensorial properties of the non-orthogonal functions play a key role for the energy minimization.

QM/QM approach for large-scale density functional calculations using non-orthogonal localized orbitals in the ONETEP program

243rd National Meeting (2012)

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