%0 journal article %@ 2040-3364 %A Sellschopp, K.,Vonbun-Feldbauer, G.B. %D 2023 %J Nanoscale %N 42 %P 16967-16975 %R doi:10.1039/D3NR01045G %T Mechanical properties of TiO2/carboxylic-acid interfaces from first-principles calculations %U https://doi.org/10.1039/D3NR01045G 42 %X Nature forms structurally complex materials with a large variation of mechanical and physical properties from only very few organic compounds and minerals. Nanocomposites made from TiO2 and carboxylic-acids, two substances that are available to nature as well as materials engineers, can be seen as representative of a huge class of natural and bio-inspired materials. The hybrid interfaces between the two components are thought to determine the overall properties of the composite. Yet, little is known about the atomistic processes at those interfaces under load and their failure mechanisms. The present work models the stress–strain curves of TiO2/carboxylic-acid interfaces in the slow deformation limit for different facets and binding modes, employing density functional theory calculations. Contrary to former hypotheses, the interface rarely fails through a de-bonding of the molecule, but rather through a surface failure mechanism. Furthermore, a stress-release mechanism is discovered for the bi-dentate binding mode on the {101} facet. Deriving mechanical properties, such as the interface strength, strain at interface failure, and the elastic modulus, allows a comparison with experimental results. The calculated strengths and elastic moduli already agree qualitatively with properties of nanocomposites, despite the simplifications in the model consisting of periodic sandwich structures. The results presented here will help to improve these materials and can be directly integrated in multi-scale simulations, in order to reach a more accurate quantitative description. %0 journal article %@ 1932-7447 %A Konuk, M.,Sellschopp, K.,Vonbun-Feldbauer, G.,Meißner, R. %D 2021 %J The Journal of Physical Chemistry C %N 8 %P 4794-4805 %R doi:10.1021/acs.jpcc.0c10338 %T Modeling Charge Redistribution at Magnetite Interfaces in Empirical Force Fields %U https://doi.org/10.1021/acs.jpcc.0c10338 8 %X Magnetite shows enormous potential from biocompatible hybrid materials to heterogeneous catalysis. However, a detailed atomistic understanding of magnetite in complex nanostructures and at interfaces is required to unfold these potentials. Methods capable of treating (several) thousands of atoms and achieving an optimal balance between accuracy and efficiency are therefore in great demand. Here, a new empirical force field for the (001) and (111) magnetite surfaces is developed using partial point charges derived from ab initio Bader charge analyses. An accurate description of electrostatic interactions enables the modeling of magnetite–organic and magnetite–water interfaces. Consequently, surface charge redistribution is proposed as the most relevant mechanism for the surface reconstruction of magnetite and the bidentate binding of ligands. The produced force field results are in excellent agreement with the latest findings on magnetite. The approach can be further applied to magnetite nanoparticles and easily extended to oxide and other ionic crystal surfaces. %0 journal article %@ 1932-7447 %A Wuerger, T.,Heckel, W.,Sellschopp, K.,Mueller, S.,Stierle, A.,Wang, Y.,Noei, H.,Feldbauer, G. %D 2018 %J The Journal of Physical Chemistry C %N 34 %P 19481-19490 %R doi:10.1021/acs.jpcc.8b04222 %T Adsorption of Acetone on Rutile TiO2: A DFT and FTIRS Study %U https://doi.org/10.1021/acs.jpcc.8b04222 34 %X Acetone adsorbed on rutile TiO2 nanoparticles was investigated with respect to its energetic, vibrational, and chemical properties. Temperature-dependent ultrahigh-vacuum Fourier transform infrared spectroscopy measurements for different acetone dosages (4.5–900 L) give insights into the acetone adsorption behavior. Those experiments indicate thermal-induced reactions of acetone on rutile TiO2 surfaces yielding new species. Density functional theory calculations were performed to investigate acetone adsorption on rutile TiO2(110). Particularly, the importance of sampling the adsorption configuration space is shown. Adsorption geometries that are energetically significantly more favorable than the commonly used high-symmetry configurations are presented. To facilitate the comparability to the experiment, theoretical infrared spectra were computed using density functional perturbation theory for various acetone adsorption geometries using different exchange-correlation functionals. Additionally, computational spectra were obtained for several species which are potential products from reactions of acetone on TiO2 surfaces. The investigated species are η2-acetate, η2-diolate, η1-enolate, and mesityl oxide. For η1-acetone, experimental and calculated spectra fit well for low temperatures, whereas for elevated temperatures, emerging bands indicate the formation of diolate.