What Is the Molecular Orbital Theory?

The molecular orbital theory is also called the molecular orbital theory or the MO method. In 1932, it was proposed by the American chemist RSMulliken and the German physicist F. Hund. It is one of the modern covalent bond theories. The main point is: discuss the structure of the molecule from the integrity of the molecule. It is believed that after the atoms form a molecule, the electron no longer belongs to an individual atomic orbital, but belongs to the molecular orbital of the entire molecule. The molecular orbital is polycentric; The atomic orbits are combined, and the molecular orbital follows the principle of energy approximation, the symmetry consistency (matching) principle, and the principle of maximum overlap, which is commonly referred to as the "three principles of bonding." The principle of electrons filling molecular orbitals in molecules also obeys energy. Least Principles, Pauli's Incompatible Principles, and Hund's Rule. ^[1]

In 1927, as we know

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1. When an atom forms a molecule, all electrons contribute, and the electrons in the molecule no longer belong to an atom, but move across the entire molecular space. Space for electrons in molecules

The principle of energy approximation, symmetry matching and maximum overlap of orbits that atomic orbitals combine to form molecular orbitals is called the three-bonding principle. ^[1]

It depends on the types of atomic orbits and the overlap between atomic orbits. For example, g1s and u1s are much lower than g2s. This is because the energy of 1s is much lower than that of 2s. Similarly, because divide

Numerous physical chemists have perfected the molecular orbital theory and developed many methods to apply molecular orbital theory to explain the structure and properties of matter.

HF Molecular orbital theory HF method

The Hartree-Fock SCF method is an ab initio method. In short, the ab initio method is to use a "correct" Hamiltonian operator. Except for the most basic constants, no more experimental data is referenced. Based on the equation, only the non-relativistic approximation, Born-Oppenheimer's fast and one-electron approximation are used to solve the Schrödinger equation and the molecular orbital calculation method.

Semi-empirical calculation of molecular orbital theory

The semi-empirical method assumes an approximate Hamiltonian operator and uses various experimental data, such as ionization energy, transition energy of electron spectrum, and bond energy, to further simplify the difficulty of integration. Hocker's molecular orbital theory (HMO) is A typical example of this approach.

Other methods of molecular orbital theory

There are also Quantum chem-istry composite methods, Quantum Monte Carlo (QM), configuration interaction (CI), multi-configuration self-consistent field method (MCSCF), multibody Perturbation theory, coupled clustering (CC) and other methods are developed based on molecular orbital theory. ^[2]