Ab initio study of the effect of substitutional impurities Mo and C on the physico mechanical characteristics of Zr(1-x)Mo(x)B2(1-y)C(2y) solid solutions

DOI: 10.62564/M4-NR1841

Nataliia Rozhenko, Liubov Ovsiannikova, Valerii Kartuzov

Frantsevich Institute for Problems of Materials Science National Academy of Science of Ukraine


Zirconium diboride is a promising material for creating ultra-high temperature ceramics (UHTK), since it is characterized by a high melting point, resistance to oxidation and thermal shock, and thermal conductivity. Varying substitutional impurities allows you to control the properties of ZrB2-based UHTK. An approach for calculating the values of the bulk modulus (B) and hardness of single crystals (HV) of solid solutions based on ZrB2 with substitutional impurities of Mo and/or C based on the results of an Ab initio study of isolated atomic clusters – fragments of their structure – has been developed and applied. The constructed clusters containing 19, 20, 45 and 87 atoms were studied within the DFT methods using Gaussian or GAMESS complexes. Within the developed approach, the cohesion energy of isolated clusters, obtained from first principles, is of decisive importance. The values of B and HV, calculated from the results of Ab initio studies of fragments of various geometries of the ZrB2 structure without impurities, turned out to be B = 197-219 GPa and HV = 22.3-24.8 GPa. The calculation results are in full agreement with experimental data B=218-250 GPa and HV=21.9-27.1 GPa. According to calculations carried out for the Zr(1-x)Mo(x)B2 at x={1/14, 1/6, 1/3, 4/9}, an increase in the Mo fraction contributes to an increase in the B by 2–13% and HV by 4–20% compared to ZrB2. For ZrB2(1-y)C(2y) at y={1/12, 1/8, 1/6, 1/3, 3/8} it is established that the greatest increase in B and HV achieved at y=1/8 (6% and 10% respectively). For the Zr(1-x)Mo(x)B2(1-y)C(2y) compound with both impurities, the largest increments are achieved at x=y=1/6 and amount to 12 and 20 (%) of the B and HV, respectively. The results obtained are in full agreement with available experimental data [1], [2], which means successful validation of the developed approach and its ability to adequately predict the values of the bulk modulus and hardness of new prognosticated ZrB2-based solid solutions.

Keywords
Zirconium diboride, substitutional impurities, Ab initio studies

Acknowledgments
This work is supported by the NATO Science for Peace and Security Programme, Project G5773.

References
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