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Media type:
E-Article
Title:
The Structural Anomaly of Zinc: Evolution of Lattice Constants and Parameters of Thermal Motion in the Temperature Range of 40 to 500 K
Contributor:
Nuss, Jürgen;
Wedig, Ulrich;
Kirfel, Armin;
Jansen, Martin
Published:
Wiley, 2010
Published in:
Zeitschrift für anorganische und allgemeine Chemie, 636 (2010) 2, Seite 309-313
Language:
English
DOI:
10.1002/zaac.200900460
ISSN:
0044-2313;
1521-3749
Origination:
Footnote:
Description:
AbstractThe crystal structure of elemental zinc deviates from the ideal hexagonal close packing by a significantly increased c/a ratio. We determined the evolution of the lattice constants and thermal displacement parameters in the temperature range of 40 to 500 K by accurate single‐crystal X‐ray diffraction. The c axis varies linearly within the whole temperature range, whereas the a lattice constant stays constant below ≈︁ 160 K, which indicates that at lower temperatures the Zn–Zn distances are no longer thermally contractible in the ab plane. As a further significant observation, the thermal expansion coefficient along the c direction exceeds the one in a direction by a factor of ~10, and consequently the c/a ratio slightly reduces, but stays unusually high (c/a = 1.826, extrapolated for T = 0 K). The thermal motion of zinc shows a striking anisotropy as expressed by a ratio U33/U11 of ≈︁ 2.6 at 500 K. This ratio decreases significantly towards lower temperatures and reaches almost 1.6 at 40 K. The thermal behavior as observed is thus reflecting the structural and bonding anisotropy of zinc at ambient conditions, but thermal motion turns isotropic at cooling, in contrast to the atomic equilibrium structure.