Bonding in CoAl and NiAl metal alloys using multipole and MEM techniques

The precise electron density distribution and bonding in metal alloys CoAl and NiAl is characterized using MEM (maximum entropy method) and multipole method. Reported X-ray single crystal data have been utilized for this purpose. Clear evidence of the metal bonding between the constituent atoms in these two systems has been obtained. The mid-bond electron densities in these systems are found to be 0.358 and 0.251 e/Å3, respectively for CoAl and NiAl in the MEM analysis. The two-dimensional maps and one-dimensional electron density profiles have been constructed and analyzed. The thermal vibration of the individual atoms Co, Ni and Al has also been studied and reported. The contraction of atoms in CoAl and expansion of Ni and contraction of Al atom in NiAl is found from the multipole analysis, in line with the MEM electron density distribution.