Magnetic moment collapse induced axial alternative compressibility of Cr 2 TiAlC 2 at 420 GPa from first principle.

The electronic structure and thermodynamical properties of Cr ₂ TiAlC ₂ 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 Mo ₂ TiAlC ₂ and hypothetical Cr ₂ TiAlC ₂ . 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 Cr ₂ TiAlC ₂ 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.