Electronic and magnetic properties of ordered and disordered binary alloy ni-al

Abstract

The order-disorder always exist in materials. The structural, electronic and magnetic properties of metals and metallic alloys have been the subject of intense research due to their applications in many technological purpose. Inter-metallic binary alloys of Ni and Al has attracted much attention in the field of science and technology because of their use in computer chips, variety of turbine components, medical implants and commercial applications etc. Magnetic properties and properties based on electronic structure of ordered alloys NiAl and Ni Al have been investigated using the first-principles study based on density functional theory and density functional perturbation theory. In order to understand the electronic properties, we have performed electronic band structure calculations. Our findings show that all the systems considered are metallic in nature. To know the contributions of the orbitals in the bands, the system is analyzed via fat bands which reveals most of the contributions on valence band of NiAl and Ni 3 Al is due to d-orbital and the contributions on conduction band is due to s and p-orbitals. Furthermore, spin up and spin down calculations have been done to know the magnetic properties of the system. Our calculations also suggest the magnetic nature of Ni Al and non-magnetic nature of NiAl. It has been found that the magnetic moment of alloys containing Ni and Al increases with increasing Ni concentration. The study of Ni Al is of great interest from magnetic point of view as it has magnetic moment 0.52 . The value of magnetic moment of NiAl and Ni Al obtained in the present work agrees with previous studies. From the study of liquid state of Ni-Al, it is found that the NiAl melt at 1873 K is ordering in nature which doesn’t support de-mixing in the solid form. 3 In studying vibrational properties, phonon modes in Ni Al are observed via phonon dispersion relation, which is di erent than that from NiAl. Optical branches gets more uniformly shifted in frequency in Ni 3 3 Al than in NiAl. Optical phonons have a non-zero frequency at the center of Brillouin zone and show no dispersion near that long wavelength limit. Modes are originated from electronic bands resulting to mode gap of 1.56 THz in NiAl and reduces the gap while increasing nickel content. Optical properties are analyzed through the calculations of dielectric function, reflectivity and refractive index. The maximum number of free electrons near the Fermi level in NiAl are responsible to change its reflectivity.