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C. Fuger, D. Holec, H. Bolvardi, H. Riedl:
"Fracture resistance characterized by bonding nature via ab initio calculations";
Poster: 47th International Conference on Metallurgical Coatings and Thin Films, ICMCTF, San Diego (USA); 2021-04-26 - 2021-04-30.

Fracture resistive thin films are of high interest, not only in the aerospace industry to improve the erosion resistance of high-performance components, but also in diverse applications in the automotive industry. As the resistance against erosion is mainly influenced by hardness and fracture resistance, it is necessary to enhance ideally both material characteristics. Initially, potential candidates are selected based on promising values of both, fracture resistance and a pronounced hardness. Screening methods by means of elastic constants evaluation (gained by DFT calculations) have evinced the previous mentioned demands for transition metal diborides [1]. The theoretically predicted ductile behaviour of various borides was confirmed in experiment, revealing also high hardness values [2].
Therefore, group V-VII transition metal diborides have been chosen to get a deeper understanding of chemical bonding and the repercussions on ductility and fracture resistance. Density functional theory using the Vienna Ab-initio Simulation Package was conducted to calculate charge density distributions of the diborides in space group 191 (α-structured, AlB2-prototype) and 194 (ω-structured, W2B5-x-prototype). For a more detailed characterization of the prevalent bonding character within this material systems, density of states has been evaluated showing also overlapping of particular electron orbitals. Furthermore, bonding properties have been investigated after deforming the crystal lattice, as also described in [3]. Strained and unstrained structures have been compared, leading to distinct differences in bonding nature and thus, indicating consequences on macroscopic material properties.