Nature of the superionic transition in Ag+ and Cu+ halides
Silver and copper halides generally display an abrupt (first-order) transition to the superionic state. However, powder diffraction studies and molecular dynamics (MD) simulations of AgI under hydrostatic pressure both indicate that a continuous superionic transition occurs on heating. The gradual o...
| Главные авторы: | , , , , , , , |
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| Формат: | Journal article |
| Язык: | English |
| Опубликовано: |
2003
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| _version_ | 1826283279814230016 |
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| author | Keen, D Hull, S Barnes, A Berastegui, P Crichton, W Madden, P Tucker, MG Wilson, M |
| author_facet | Keen, D Hull, S Barnes, A Berastegui, P Crichton, W Madden, P Tucker, MG Wilson, M |
| author_sort | Keen, D |
| collection | OXFORD |
| description | Silver and copper halides generally display an abrupt (first-order) transition to the superionic state. However, powder diffraction studies and molecular dynamics (MD) simulations of AgI under hydrostatic pressure both indicate that a continuous superionic transition occurs on heating. The gradual onset of the highly conducting state is accompanied by an increasing fraction of dynamic Frenkel defects, a peak in the specific heat and anomalous behavior of the lattice expansion. Similar methods have been employed to investigate the proposed continuous superionic transition between the two ambient pressure face centered cubic phases of CuI. This is difficult to examine experimentally, because the hexagonal β phase exists over a narrow temperature range between the γ (cation ordered) and a (cation disordered) phases. MD simulations performed with the simulation box constrained to remain cubic at all temperatures show that, although limited Cu+ Frenkel disorder occurs within γ-CuI, CuI undergoes an abrupt superionic transition at 670 K to the superionic a phase. This is supported by powder neutron diffraction studies of CuI lightly doped with Cs+ to prevent stabilization of the β phase. The implications of these results on the phase transitions of other copper and silver halide superionic conductors are discussed. |
| first_indexed | 2024-03-07T00:56:32Z |
| format | Journal article |
| id | oxford-uuid:8843bf23-8150-47df-be78-478349a1a60a |
| institution | University of Oxford |
| language | English |
| last_indexed | 2024-03-07T00:56:32Z |
| publishDate | 2003 |
| record_format | dspace |
| spelling | oxford-uuid:8843bf23-8150-47df-be78-478349a1a60a2022-03-26T22:16:04ZNature of the superionic transition in Ag+ and Cu+ halidesJournal articlehttp://purl.org/coar/resource_type/c_dcae04bcuuid:8843bf23-8150-47df-be78-478349a1a60aEnglishSymplectic Elements at Oxford2003Keen, DHull, SBarnes, ABerastegui, PCrichton, WMadden, PTucker, MGWilson, MSilver and copper halides generally display an abrupt (first-order) transition to the superionic state. However, powder diffraction studies and molecular dynamics (MD) simulations of AgI under hydrostatic pressure both indicate that a continuous superionic transition occurs on heating. The gradual onset of the highly conducting state is accompanied by an increasing fraction of dynamic Frenkel defects, a peak in the specific heat and anomalous behavior of the lattice expansion. Similar methods have been employed to investigate the proposed continuous superionic transition between the two ambient pressure face centered cubic phases of CuI. This is difficult to examine experimentally, because the hexagonal β phase exists over a narrow temperature range between the γ (cation ordered) and a (cation disordered) phases. MD simulations performed with the simulation box constrained to remain cubic at all temperatures show that, although limited Cu+ Frenkel disorder occurs within γ-CuI, CuI undergoes an abrupt superionic transition at 670 K to the superionic a phase. This is supported by powder neutron diffraction studies of CuI lightly doped with Cs+ to prevent stabilization of the β phase. The implications of these results on the phase transitions of other copper and silver halide superionic conductors are discussed. |
| spellingShingle | Keen, D Hull, S Barnes, A Berastegui, P Crichton, W Madden, P Tucker, MG Wilson, M Nature of the superionic transition in Ag+ and Cu+ halides |
| title | Nature of the superionic transition in Ag+ and Cu+ halides |
| title_full | Nature of the superionic transition in Ag+ and Cu+ halides |
| title_fullStr | Nature of the superionic transition in Ag+ and Cu+ halides |
| title_full_unstemmed | Nature of the superionic transition in Ag+ and Cu+ halides |
| title_short | Nature of the superionic transition in Ag+ and Cu+ halides |
| title_sort | nature of the superionic transition in ag and cu halides |
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