| Autor: |
Mozharivskyj, Yurij, Pecharsky, Alexandra O., Bud'ko, Sergej, Franzen, Hugo F. |
| Zdroj: |
Zeitschrift für anorganische und allgemeine Chemie; July 2002, Vol. 628 Issue: 7 p1619-1630, 12p |
| Abstrakt: |
Crystal structures of the compounds SmCu1+δAs2—χPχ(δ= 0 — 0.2, χ= 0 — 2) undergoing symmetry‐breaking transitions and SmCuP2.3have been investigated by the X‐ray single crystal and powder methods. While the phases SmCuAs2through SmCuAs1.22P0.78retain the tetragonal HfCuSi2structure (P4/nmmspace group), the compounds SmCuAs1.11P0.89through SmCuAs0.56P1.44adopt the GdCuAs1.15P0.85—type structure (Pmmnspace group), an orthorhombic variant of the HfCuSi2‐type. Further distortion follows in SmCuAs0.33P1.67through SmCuP2.3, the powder patterns of which were indexed in the P2/nspace group (P2/cin a standard setting). According to Landau theory the transitions from tetragonal SmCuAs1.22P0.78to orthorhombic SmCuAs1.11P0.89and from orthorhombic SmCuAs0.56P1.44to monoclinic SmCuAs0.33P1.67can be continuous. Introducing extra copper into some of the orthorhombic arsenophosphides restabilizes tetragonal phases (0 < δ≤ 0.2) with the P4/nmmsymmetry, and the reverse transition Pmmn→ P4/nmmcan be continuous. Inserting copper atoms into monoclinic SmCuP2yields the SmCu1+δP2phosphides with Cmmmsymmetry, and this transition is first‐order. |
| Databáze: |
Supplemental Index |
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