Magnetic moment collapse induced axial alternative compressibility of Cr2TiAlC2 at 420 GPa from first principle

Abstract

The electronic structure and thermodynamical properties of Cr2TiAlC2 are studied by first principles under pressure. The obtained results observed that the ferromagnetic order is the most stable ground state and the magnetic moment will collapse at about 50 GPa. As a result, the lattice a axis becomes stiffer above about 420 GPa, ultimately presenting the same axial compressibility trends with those of nonmagnetic compounds Mo2TiAlC2 and hypothetical Cr2TiAlC2. The elastic constants and phonon dispersion curves demonstrate the structural stability during the disappearance of magnetic moment and occurrence of axial alternative compressibility. The density of states and energy band calculations confirmed the existence of magnetic moment of Cr2TiAlC2 at 0 GPa and disappearance at high pressures above 50 GPa. Evolutions of magnetic moment collapse with pressure are confirmed by a variety of properties. The obtained grüneisen parameter and thermal expansion coefficients show the maximum value among the known MAX phases, to date and to the author’s knowledge.

Pressure-induced magnetic moment abnormal increase in Mn2FeAl and non-continuing decrease in Fe2MnAl via first principles

“…In particular, Mn(A) exhibits a peak at Fermi level but Mn(B) and Fe locate at the steep hill, both of which make the charge transfer easier with respect to that of Fe 2 MnAl, consisting with the fact of its lower magnetism collapse pressure. Cr ion moment collapse process has been deeply discussed in Cr 2 TiAlC 2 20 , in which the contrary charge shift direction causes the moment collapse, whereas the present moment collapse of Fe and Mn show only certain shift under pressure. The DOS profiles of Fe 2 MnAl and Mn 2 FeAl consists well with their energy band profiles, as shown in Figs 7 and 8.…”

Predictive theoretical screening of phase stability for chemical order and disorder in quaternary 312 and 413 MAX phases

“…Note that the o-MAX structure has previously been shown to be dynamically stable. 33,34 In the present work we considered M′ and M″ from groups 3 to 6; Sc, Y, Ti, Zr, Hf, V, Nb, Ta, Cr, Mo, and W. To model chemical disorder of M′ and M″ on the M sublattices we used the special quasi-random structure (SQS) method 35 with supercell sizes of 4 × 4 × 1 unit cells, i.e. 192 and 256 atoms for the 312 and 413 MAX phases, respectively.…”