ISBN 9783843950725

978-3-8439-5072-5, Reihe Theoretische Chemie

Joseph Daniel Schmitt-Monreal
Applications of Subsystem-Quantum Chemistry to Materials and Surfaces

150 Seiten, Dissertation Technische Universität Braunschweig (2021), Softcover, B5

Zusammenfassung / Abstract

Applying computational chemistry to materials and surfaces requires the use of multiscale simulation methods. Here, two complementary approaches were considered.

First, the use of atomistic simulations using periodic density-functional theory (pDFT) for obtaining parametrized models of the interaction of metal oxide surfaces with molecules was explores. Based on pDFT calculations a model of the interaction energies was developed and compared to a specifically designed AFM experiment.

Second, fragmentation methods offer an attractive approach for the quantum-chemical treatment of large molecular clusters and crystals. Here, the combination of two complementary approaches of fragmentation methods were explored, the many-body expansion (MBE) and the frozen-density embedding (FDE). Conventionally, the MBE is performed for the total energy, but such an energy-based MBE often suffers from a slow convergence with respect to the expansion order, which can be only slightly enhanced by accounting the environmental effects on the subsystems using FDE.

An alternative yet very promising approach called density-based MBE was established, by performing the MBE for the electron density instead of the total energy allowing to derive a density-based correction for all higher order polarization effects.

In further tests of water clusters, a systematic assessment of the accuracy of the density-based MBE shows significant accelerations of the interaction energy convergence. The density-based MBE reproduces interaction energies per fragment within chemical accuracy already at low-order expansions and allows to accurately predict the energetic ordering as well as the relative interaction energies of different isomers of water clusters