Repulsive Interaction Potentials between Rare-Gas Atoms. Heteronuclear Two-Center Systems

A theoretical expression, previously applied only to homonuclear pairs of rare-gas atoms, has been used to calculate the interaction energies $U\left(R\right)\mathrm{}$ for the corresponding heteronuclear two-center systems at inter-nuclear separations $R$ ranging from $0.01a_0$ to $\sim 6.0a_0 (a_0=0.529\mathrm{} \mathrm{\AA })$. These results are compared with: (a) empirical data; (b) other calculations; (c) the geometric-mean rule $U_{\mathrm{AB}}={\left(U_{\mathrm{AA}}{U}_{\mathrm{BB}}\right)}^{\frac{1}{2}}$; (d) the corresponding united-atom energies. With regard to (a) and (b), this comparison supports conclusions drawn previously from a study of the homonuclear pairwise interactions. That is, the present calculations, too, generally agree more closely with experiment than does either Bohr's screened Coulomb potential or Firsov's Thomas-Fermi type potential. Relation (c) is found to be satisfied, generally, to within a few percent. As for (d), calculations for the He-Ne and Ar-Kr systems indicate that, as $R\to 0$, the electron energy of each system tends, approximately, to the appropriate empirical united-atom value. A similar study of other systems, including the light gases, metals, and certain diatoms, is in progress.