Empirical equations for the bond energies and vibrational frequencies at chemisorptive bonds on surfaces

Empirical equations derived for bond energies and force constants of gaseous molecules are applied to chemisorptive bonds on surfaces. For two adsorbed atoms from the same family of the periodic table, A and B, the chemisorptive bond energies, E, to the same metal, M, can be approximated by E_A–M/E_B-M ≈ (E_A2/E_B2)^{$\text{1}\text{2}$}, where E_A2 and E_B2 are the bonds energies of diatomic molecules A₂ and B₂, respectively The corresponding vibrational frequencies, ν, can be approximated by ν²_A–M/ν²_B-M ≈ (m_B/m_A)(F_A2/F_B2)^{$\text{1}\text{2}$} · m_A and m_B are the masses of atoms A and B, respectively;F_A2 and F_B2 are the force constants of molecules A₂ and B₂, respectively. These relations are applied to the chemisorption of halogens on metals and showed good agreement with experiment.