Research on the Structure and Properties of Diamond-Like Quaternary Compounds MCu₂GeX₄ (M = Fe, Co; X = S, Se)

In this article the electrical, magnetic, and mechanical properties of the quaternary compound MCu₂GeX₄ (M = Fe, Co; X = S, Se) have been systematically investigated using a first-principles calculation method. The calculation results show that the ground state of the quaternary compound MCu₂GeX₄ is in antiferromagnetic state, and the two magnetic states of the quaternary compound MCu₂GeX₄ exhibit different material characteristics, some are metallic, some are semi-metals, and some exhibit semiconductor characteristics under the exchange-correlation generalized function (PBE) calculation method. Among them, the magnetic sources of the ferromagnetic states are mainly caused by the strong spin-splitting effects on the d orbitals of Fe and Co atoms. However, all these four materials exhibit semiconducting characteristics under calculations using the hybrid functionals (HSE06). In order to study electronic structures under strain, we have also investigated the mechanical properties of MCu₂GeX₄ structures. We found that these materials have good mechanical stability, and the Young's modulus and shear modulus of the materials exhibit different degrees of anisotropy. Finally, we investigated the total energy, band gap, and magnetic moment of M atoms of MCu₂GeX₄ under the tetragonal strain effect. The results show that the total energy, band gap, and magnetic moment of these materials change regularly with the strain on the atoms in different directions. This study can provide comprehensive information on the various properties of MCu₂GeX₄ and provide useful references for its future applications.