| Autor: |
Bocharov, D., Krack, M., Rafalskij, Yu., Kuzmin, A., Purans, J. |
| Rok vydání: |
2020 |
| Předmět: |
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| Zdroj: |
Comp. Mater. Sci. 171 (2020) 109198 |
| Druh dokumentu: |
Working Paper |
| DOI: |
10.1016/j.commatsci.2019.109198 |
| Popis: |
Scandium fluoride (ScF3) belongs to a class of negative thermal expansion (NTE) materials. It shows a strong lattice contraction up to about 1000 K switching to expansion at higher temperatures. Here the NTE effect in ScF3 is studied in the temperature range from 300 K to 1600 K using ab initio molecular dynamics (AIMD) simulations in the isothermal-isobaric (NpT) ensemble. The temperature dependence of the lattice constant, inter-atomic Sc-F-Sc bond angle distributions and the Sc-F and Sc-Sc radial distribution functions is obtained as a function of supercell size from 2a x 2a x 2a to 5a x 5a x 5a where a is the lattice parameter of ScF3. A comparison with the experimental Sc K-edge EXAFS data at 600 K is used to validate the accuracy of the AIMD simulations. Our results suggest that the AIMD calculations are able to reproduce qualitatively the NTE effect in ScF3, however a supercell size larger than 2a x 2a x 2a should be used to account accurately for dynamic disorder. The origin of the NTE in ScF3 is explained by the interplay between expansion and rotation of ScF6 octahedra. |
| Databáze: |
arXiv |
| Externí odkaz: |
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