Features of structure and phase transitions in pure uranium and U–Mo alloys: atomistic simulation
| Autor: | V.I. Tseplyaev, A. Yu. Kuksin, D.E. Smirnova, L.N. Kolotova, Sergey Starikov |
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| Rok vydání: | 2016 |
| Předmět: |
010302 applied physics
History Phase transition Materials science Condensed matter physics chemistry.chemical_element Pair distribution function 02 engineering and technology Uranium 021001 nanoscience & nanotechnology 01 natural sciences Computer Science Applications Education Condensed Matter::Materials Science Tetragonal crystal system Molecular dynamics chemistry Lattice (order) Metastability 0103 physical sciences Density functional theory 0210 nano-technology |
| Zdroj: | Journal of Physics: Conference Series. 774:012036 |
| ISSN: | 1742-6596 1742-6588 |
| Popis: | We study structural properties of cubic and tetragonal phases of U-Mo alloys using atomistic simulations: molecular dynamics and density functional theory. For pure uranium and U-Mo alloys at low temperatures we observe body-centered tetragonal (bct) structure, which is similar to the metastable γ°-phase found in the experiments. At higher temperatures bct structure transforms to a quasi body-centered cubic (q-bcc) phase that exhibits cubic symmetry just on the scale of several interatomic spacings or when averaged over time. Instantaneous pair distribution function (PDF) differs from PDF for the time-averaged atomic coordinates corresponding to the bcc lattice. The local positions of uranium atoms in q-bcc lattice correspond to the bct structure, which is energetically favourable due to formation of short U-U bonds. Transition from bct to q-bcc could be considered as ferro-to paraelastic transition of order-disorder type. The temperature of transition depends on Mo concentration. For pure uranium it is equal to about 700 K, which is well below than the upper boundary of the stability region of the α-U phase. Due to this reason, bct phase is observed only in uranium alloys containing metals with low solubility in α-U. |
| Databáze: | OpenAIRE |
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