Onishi - Quantum Computational Chemistry: Modelling and Calculation for Functional Materials

Springer Nature Singapore Pte Ltd. 2018

Taku Onishi 1, 2, 3

Abstract

By the difference of scale, matter is largely classified into solid, molecule and cluster. The basis unit of matter is atom. Atom consists of quantum particles such as electron, proton and neutron. In Bohr model, quantum effect is incorporated through the concept of matter wave. In the case of hydrogen, the orbit radius was estimated to be 0.5292 , corresponding to the experimental distance. In addition, the discrete energy was also reproduced. However, Bohr model was not able to be applicable to many-electron system. In order to incorporate particle-wave duality in universal manner, quantum wave-function was proposed. In wave-function theory, electron does not correspond to classical point, but spreads as wave. It is difficult to interpret wave-function itself. It is because it does not represent figure. Instead, the square of wave-function represents electron density. Wave-function can be obtained by solving the Schrdinger equation, where electron energy is given by operating wave-function with Hamiltonian. As a feature of wave-function, it is normalized and satisfies orthogonality. In quantum mechanics, one electron occupies one wave-function. It implies that one electron is not distributed to several wave-functions.

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