Summary and Future

Abstract

At the beginning of last century, it was difficult to extend quantum theory to many-electron system. In Bohr model, the electron structure of hydrogen atom was reproduced by introducing the concept of matter wave. However, it could not be applicable for many-electron system. To represent electron as quantum particle, the wave-function was proposed. One electron is allocated in one wave-function. It is not split into two wave-functions. Though the basic equation of electrons is Schrödinger equation, it cannot be analytically solved. Hartree-Fock method was developed to solve it numerically. It is important to analyse the obtained wave-function, which stands for molecular orbital. By using chemical bonding rule, chemical bonding character is specified. Though natural orbital is often utilized in molecular orbital analysis, it is completely different from molecular orbital. DFT is the scientifically reasonable method, due to incorporation of electron correlation effect. It makes it possible to design advanced materials. Finally, the future research in collaboration with particle physics is explained.