Europhys. Lett.
Volume 67, Number 5, September 2004
Page(s) 807 - 813
Section Condensed matter: structure, mechanical and thermal properties
Published online 01 August 2004
Europhys. Lett., 67 (5), pp. 807-813 (2004)
DOI: 10.1209/epl/i2004-10119-4

A new polymorphic material? Structural degeneracy of $\chem{ZrMn_{2}}$

Xing-Qiu Chen1, 2, W. Wolf3, R. Podloucky1, P. Rogl1 and M. Marsman4

1  Institut für Physikalische Chemie, Universität Wien - Liechtensteinstrasse 22A A-1090, Vienna, Austria
2  School of Materials and Metallurgy, Northeastern University Shenyang 110004, PRC
3  Materials Design s.a.r.l. - 44 av. F.-A. Bartholdi, F-7200 Le Mans, France
4  Institut für Materialphysik, Universität Wien - Sensengasse 8 A-1090, Vienna, Austria

(Received 26 March 2004; accepted in final form 21 June 2004)

Based on density-functional calculations, we propose that $\chem{ZrMn_{2}}$ is a polymorphic material. We predict that at low temperatures the cubic $\chem{C15}$, and the hexagonal $\chem{C14}$ and $\chem{C36}$ structures of the Laves phase compound $\chem{ZrMn_{2}}$ are nearly equally stable within 0.3 $\un{kJ\,mol^{-1}}$ or 30 $\un{K}$. This degeneracy occurs when the $\chem{Mn}$ atoms magnetize spontaneously in a ferromagnetic arrangement forming the states of lowest energy. From the temperature-dependent free energies at $T\approx 160$ $\un{K}$ we predict a transition from the most stable $\chem{C15}$ to the $\chem{C14}$ structure, which is the experimentally observed structure at elevated temperatures.

61.50.Lt - Crystal binding; cohesive energy.
71.15.Nc - Total energy and cohesive energy calculations.
75.50.-y - Studies of specific magnetic materials.

© EDP Sciences 2004