In this work, we present binding energies of acetic acid on the (110), (100), and (011) surfaces of rutile TiO 2 calculated with the two density functional theory (DFT) exchange-correlation functionals PBE and PBEsol. It is shown that the binding energies can be influenced, in this case slightly reduced for all three surfaces, via preadsorption of hydrogen. Additionally, we tested the performance of the densityfunctional based tight-binding (DFTB) method applied to these adsorbate systems. Analysis of the electronic density of states shows that DFTB provides qualitatively comparable results to DFT calculations as long as the Fermi energy level remains within the band gap.
Components distort during directed energy deposition (DED) additive manufacturing (AM) due to the repeated localised heating. Changing the geometry in such a way that distortion causes it to assume the desired shape -a technique called distortion-compensation -is a promising method to reach geometrically accurate parts. Transient numerical simulation can be used to generate the compensated geometries and severely reduce the amount of necessary experimental trials. This publication demonstrates the simulation-based generation of a distortioncompensated DED build for an industrial-scale component. A transient thermo-mechanical approach is extended for large parts and the accuracy is demonstrated against 3d-scans. The calculated distortions are inverted to derive the compensated geometry and the distortions after a single compensation iteration are reduced by over 65%.
In this work, we study the adhesion and decohesion of Cu(1 0 0) surfaces using density functional theory (DFT) calculations. An upper stress to surface decohesion is obtained via the universal binding energy relation (UBER), but the model is limited to rigid separation of bulk-terminated surfaces. When structural relaxations are included, an unphysical size effect arises if decohesion is considered to occur as soon as the strain energy equals the energy of the newly formed surfaces. We employ the nudged elastic band (NEB) method to show that this size effect is opposed by a size-dependency of the energy barriers involved in the transition. Further, we find that the transition occurs via a localization of bond strain in the vicinity of the cleavage plane, which resembles the strain localization at the tip of a sharp crack that is predicted by linear elastic fracture mechanics.
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