[Zurück]

X. Yan, X. Chen, H. Michor, W. Wolf, V. Witusiewicz, E. Bauer, R. Podloucky, P. Rogl:
"Structural, thermodynamic, and electronic properties of Laves-phase NbMn₂ from first principles, x-ray diffraction, and calorimetric experiments";
Physical Review B, 97 (2018), 125110; S. 1 - 10.

By combining theoretical density functional theory (DFT) and experimental studies, structural and magnetic phase stabilities and electronic structural, elastic, and vibrational properties of the Laves-phase compound NbMn₂ have been investigated for the C14, C15, and C36 crystal structures. At low temperatures C14 is the ground-state structure, with ferromagnetic and antiferromagnetic orderings being degenerate in energy. The degenerate spin configurations result in a rather large electronic density of states at Fermi energy for all magnetic cases, even for the spin-polarized DFT calculations. Based on the DFT-derived phonon dispersions and densities of states, temperature-dependent free energies were derived for the ferromagnetic and antiferromagnetic C14 phase, demonstrating that the spin-configuration degeneracy possibly exists up to finite temperatures. The heat of formation Δ₂₉₈H⁰= −45.05 ± 3.64 kJ (mol f.u. NbMn2)⁻¹ was extracted from drop isoperibolic calorimetry in a Ni bath. The DFT-derived enthalpy of formation of NbMn₂ is in good agreement with the calorimetric measurements. Second-order elastic constants for NbMn2 as well as for related compounds were calculated.

Laves-phases, DFT calculations, x-ray diffraction

http://dx.doi.org/10.1103/PhysRevB.97.125110