First Principle Study of MC (M= Al, Ga, and In) at Equilibrium and under Negative Stress

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The electronic and magnetic properties of the hypothetical compounds of MC (M=Al, Ga and In) are investigated by using first-principle calculations and pseudopotential plane wave self-consistent field method based on density functional theory. In order to find the most stable phase of MC (M=Al, Ga and In), we study them in zinc-blende (ZB), rocksalt (RS), wurtzite and NiAs crystal structures. We find that the most stable crystal structure is the RS structure by comparing the total energies of these compounds in different structures. Our calculations show that these compounds are metals in all of these structures. However, many of the nanospintronic devices are the heterojunctions of half-metals and semiconductors where the crystal structures of the layers that are grown on the semiconductors are the same as that of the semiconductors. Because most of the semiconductors have ZB structure, we investigate the electronic and magnetic properties of these compounds in this structure. It is shown that although MC (M=Al, Ga and In) compounds are metals in ZB structure, they become half-metal when relatively high negative stresses are applied over them. Therefore these compounds could be used in spintronic devices.