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Pressure is a fundamental tool that can induce structural and electronic transformations, which is helpful to search for exotic materials not accessible at ambient conditions. Here, we have performed an extensive structural study on cubic Mg 3 As 2 in a pressure range of 0-100 GPa by using a combination of structure predictions and first-principle calculations. Interestingly, two novel structures with space groups C2/m and P 1 were uncovered that become energetically most stable at pressures of 12 GPa and 30 GPa, respectively. Phonon dispersions demonstrate that the three phases are dynamically stable in their respective low-enthalpy pressure ranges. The electronic calculations show that Mg 3 As 2 keeps semiconductor properties at pressures up to 100 GPa. The interesting thing is that the direct semiconducting property of Mg 3 As 2 transforms into indirect semi-conducting when the pressure is above 12 GPa. The current results provide new insights for understanding the behavior of Mg 3 As 2 at high pressures.

The rational design of ferromagnetic materials is crucial for the development of spintronic devices. Using first-principles structural search calculations, we have identified 73 two-dimensional transition metal hydrides. Some of them show interesting magnetic properties, even when combined with the characteristics of the electrides. In particular, the P3̅m1 Fe2H monolayer is stabilized in a 1T-MoS2-type structure with a local magnetic moment of 3 μB per Fe atom, whose robust ferromagnetism is attributed to the exchange interaction between neighboring Fe atoms within and between sublayers, leading to a remarkably high Curie temperature of 340 K. On the other hand, it has a large magnetic anisotropic energy and spin-polarization ratio. Interestingly, the above room-temperature ferromagnetism of the Fe2H monolayer is well preserved within a biaxial strain of 5%. The structure and electron property of surface-functionalized Fe2H are also explored. All of these interesting properties make the Fe2H monolayer an attractive candidate for spintronic nanodevices.