First principles study on the structural, electronic and magnetic properties of Ni4C

The first-principles calculations were performed based on density functional theory to study the structural, electronic and magnetic properties of Ni4C resulting from carbon atom diffusion in a conventional Ni unit cell. Firstly, geometry optimization was performed to reach the equilibrium state of Ni4C. The lattice constant of the stable Ni4C crystal structure was larger than that of the Ni unit cell. Then the electronic and magnetic properties of Ni4C were determined, and the results showed that the magnetic moment was 0.46 μB per unit cell, and the calculated local magnetic moment of carbon atoms was 0. There were two occupied sites for Ni atoms with different local magnetic moments, which was about 0.64 μB (close to that of nickel unit cell) for Nia atoms at the top corners and a negative value of −0.06 μB for Nib atoms at the face center. The magnetic moment increased abruptly to 1.89 μB at 3.79 Å due to the changes of lattice parameters with external factors, and fluctuated slowly from 3.5 Å to 3.78 Å.