Calculation and analysis of common harmonic force field of tetrahedral molecules EhX4(Eh=C,Si,Ge,Sn,Pb; X=H,F,Cl,Br,I)

The method of finding force constants (FC) of multiatomic molecules by direct differentiation of effective potentials satisfactorily describing both normal molecule oscillations and its energetics is suggested. The general analytical expressions for all FC of the tetrahedral molecule are suggested. FC for EhX4 (Eh=C, Si, Ge, Sn, Pb; X=H, F, Cl, I) are found. It is shown that the partial energy of Eh-X bond dissociation found linearly correlates with experimentally found length values of these bonds