Investigation of molecular structure by the electron diffraction- and theoretical+calculation methods

Results are presented of investigation into molecular structure, carried out by Ivanovski Chemical-Technological Institute (IChTT) together with the Moscow University by gas electron diffraction-, model-, and quantum-chemical calculation methods. Molecules of tetrahalogenides of rare earth elements, cyclic Li2F2 and Tl2F2 molecules were studied by the gas electron diffraction method. Within the framework of theoretical investigations on the basis of an ion model of molecules for MX halides of alkali metals, M3X halides (M3=Ga, In, Tl), M2X2 and M23X3 dimeric molecules the atomization energy is determined the equilibrium geometric parameters, force fields, vibration frequencies and mean amplitudes of nuclei vibrations are calculated. A complex program for calculation of the structure, binding energy and force fields is developed. The main direction in the quantum-mechanical calculations in IChTI is the determination of force fields and spectroscopic parameters of molecules and ions, as experimental methods fail to give reliable results to that effect. In this connection a systematic research is going on, to determine the effect of a basic set of functions on finding the data on force fields of multi-atom molecules and ions, comprised of 2d-period atoms, using the SCF MO LCAO method