Phase diagrams of incommensurate ferroelectric NH₄HSeO₄: phenomenological treatment
The phenomenological analysis of the pressure-temperature (P −T ) phase diagram of NH₄HSeO₄ crystals is presented. It is shown that the disagreement between the experimental results and the theory may be removed assuming that the coefficient of the Landau free-energy expansion κ at the gradient te...
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| Datum: | 2000 |
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| Hauptverfasser: | , |
| Format: | Artikel |
| Sprache: | English |
| Veröffentlicht: |
Інститут фізики конденсованих систем НАН України
2000
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| Schriftenreihe: | Condensed Matter Physics |
| Online Zugang: | http://dspace.nbuv.gov.ua/handle/123456789/120993 |
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| Назва журналу: | Digital Library of Periodicals of National Academy of Sciences of Ukraine |
| Zitieren: | Phase diagrams of incommensurate ferroelectric NH₄HSeO₄: phenomenological treatment / A.V. Kityk, A.V. Zadorozhna // Condensed Matter Physics. — 2000. — Т. 3, № 4(24). — С. 759-766. — Бібліогр.: 9 назв. — англ. |
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Digital Library of Periodicals of National Academy of Sciences of Ukraine| Zusammenfassung: | The phenomenological analysis of the pressure-temperature (P −T ) phase
diagram of NH₄HSeO₄ crystals is presented. It is shown that the disagreement between the experimental results and the theory may be removed
assuming that the coefficient of the Landau free-energy expansion κ at the
gradient term (dq/dz)(dq∗/dz) changes the sign in the experimental range
of pressures. According to the present model the triple point observed in
NH₄HSeO₄ at PK ≈ 455 MPa, TK ≈ 236 K may be considered as artificial
points which result from the limitation of experimental resolution. Therefore, even above PK there still exist two very close (unresolved) lines of the
incommensurate phase transitions. |
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