ELECTROSTATIC MODEL OF COVALENT BONDING. A PARTICULAR SOLUTION OF THE HELLMANN – FEYNMAN ELECTROSTATIC THEOREM

The purpose of this work was to create a model of a covalent bond based on quasi-classical electrostatic concepts. A three-center electrostatic model of a covalent bond has been proposed, which takes into account only the forces that occur along the axis connecting the nuclei of the bonded atoms. These electrostatic forces are represented as gradients of the potential energy of the atoms from their isolated state to their bonded state. According to the model concept, in the equilibrium state of a molecular system, the charges of the nucleus and the electron density, which is reduced to a point along the axis connecting the nuclei of the bonded atoms, are aligned in each of these atoms. In diatomic molecules, the force equilibrium between the bonded atoms is achieved by the equality of forces (and electrostatic potentials) between the nuclei of the bonded atoms and the electrostatic tension forces on the reverse side of the nuclei, ensuring zero ponderomotive forces on the nuclei. In polyatomic molecules, the electrostatic tension forces maintain equilibrium only for the nuclei of the terminal atoms. In polyvalent atoms, depending on the valence angles (α), these forces may be absent (α=180o) or partially realized (180o>α>90o). The revealed simple functional dependence of the electrostatic potentials of the bond atoms allows us to calculate the energy or length of a chemical bond for a known (or specified) value of the interatomic distance or bond energy, respectively, with an accuracy not lower than the error of their experimental determination. The results obtained indicate the promising nature of the study of molecular systems based on electrostatics, and may be useful in quantum chemistry to identify the difference in the topography of the electron density in chemically bonded and isolated atoms.