Abstract
Based on density-functional calculations, we propose that ZrMn2 is a polymorphic material. We predict that at low temperatures the cubic C15, and the hexagonal C14 and C36 structures of the Laves phase compound ZrMn2 are nearly equally stable within 0.3 kJ mol−1 or 30 K. This degeneracy occurs when the Mn atoms magnetize spontaneously in a ferromagnetic arrangement forming the states of lowest energy. From the temperature-dependent free energies at T ≈ 160 K we predict a transition from the most stable C15 to the C14 structure, which is the experimentally observed structure at elevated temperatures.