Structural, vibrational and optical characters of Ni-AI

The structural, vibrational and optical properties of inter-metallic ordered compound Ni-AI are carried out in the framework of density functional theory. Phonon bands are found more uniformly shifted in frequency in Ni₃ Al than in NiAl. 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. (author)