Topological analysis of the charge density response of a Ni₄ cluster to a probe H₂ molecule

Local density self-consistent field (SCF) discrete variational Xα calculations are performed on a Ni₄ tetrahedron interacting with a probe H₂ molecule in special geometries. Optimized basis functions generated from the spherically averaged SCF potential are used. Topological charge-density analyses and binding energy calculations are used to study a portion of the energy surface for the approach of the H₂ molecule toward the Ni₄ tetrahedron. The effect of the H₂ molecule on Ni-Ni, Ni-H bonds and changes in the H-H covalent bond are investigated with the help of the ∇_ρ field and various data at its critical points. The qualitative relationship between these data and the calculated binding energies is exploited.