Resolution of the 66-Fold Superstructure of DySe1.84 by X-ray Diffraction and Second-Moment Scaled Hückel Calculations
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- 作者：A. van der Lee ; L. M. Hoistad ; M. Evain ; B. J. Foran ; and S. Lee
- 刊名：Chemistry of Materials
- 出版年：1997
- 出版时间：January 1997
- 年：1997
- 卷：9
- 期：1
- 页码：218 - 226
- 全文大小：223K
- 年卷期：v.9,no.1(January 1997)
- ISSN：1520-5002
文摘
We report the superlattice of the modulated structureDySe1.84. The modulation is of thecharge density wave type, associated with electronic states on seleniumatoms arranged intwo-dimensional square nets. The complete modulated structure canbe described in thesuperspace group formalism in a 3+2 dimensional space group
.The basic cellobserved by single-crystal X-ray diffraction is orthorhombic witha = 3.9912(3) Å, b =3.9863(1) Å, and c = 8.206(1) Å. The modulation wavevectors are q1 =
a*+
b* +1/2c* andq2= a* - b* +1/2c*, where =0.33338(16) and = 0.27284(6). Structurerefinementbased on first- and second-order satellites as well as main latticereflections producedsolutions in four different space groups that could not bedifferentiated on the basis ofagreement factors. A best solution was sought by use ofsecond-moment scaled, tight-bindingband calculations. The lowest energy model found was similar tobut not identical with twoof those refined for X-ray data. This lowest energy structure canbe rationalized by analysisof second-nearest-neighbor interactions within the selenium squarenets.
.The basic cellobserved by single-crystal X-ray diffraction is orthorhombic witha = 3.9912(3) Å, b =3.9863(1) Å, and c = 8.206(1) Å. The modulation wavevectors are q1 =a*+b* +1/2c* andq2= a* - b* +1/2c*, where =0.33338(16) and = 0.27284(6). Structurerefinementbased on first- and second-order satellites as well as main latticereflections producedsolutions in four different space groups that could not bedifferentiated on the basis ofagreement factors. A best solution was sought by use ofsecond-moment scaled, tight-bindingband calculations. The lowest energy model found was similar tobut not identical with twoof those refined for X-ray data. This lowest energy structure canbe rationalized by analysisof second-nearest-neighbor interactions within the selenium squarenets.