Electron diffraction data have been used as a constraint in the determination of force field for Tl2F2 having planar rhombic structure. The L-F approximation method, recently given by us, has also been applied to evaluate force constants for thallous halide dimers,e.g. T12F2 and T12Cl2. The results have been compared with the available experimental data in order to check the validity of the present work. It is concluded that non-bond experimental mean amplitudeU1...Tl for Tl2F2 is capable of fixing the force field and L-F approximation gives reasonably good force fields for the two thallous halide dimers now under study.
