ABSTRACT
Computer simulation methods are classified in accordance with the size and time scale for the target phenomenon. They include quantum mechanics dealing with electronic states, molecular dynamics and Monte Carlo simulation dealing with the collective motion of atoms and molecules, finite element method and statistical thermodynamics calculation dealing with bulk materials, and phase-field method dealing with a mesoscale that connects between micro and the macro scaled phenomena. This chapter focuses on the molecular orbital method, which is widely used as a calculation method based on quantum mechanics. Currently available molecular orbital simulations are based on a method with higher accuracy that considers electron correlation (the many-body perturbation method, the configuration interaction (CI) method) or density functional theory with a high accuracy per number of calculations. Molecular orbital simulations consume computational resources particularly for systems with many atoms and electrons.
