Density Functional Theory Calculations for Materials with Complex Structures

Quantum-mechanics-based first-principles density functional theory (DFT) calculations are promising for elucidating the relationship between structures and physical properties at the atomic scale. DFT calculations are highly accurate but conventionally time consuming, which limits the application of DFT to materials having complex structures and reactions affected by many metastable states. To overcome this problem, multi-scale simulations have been conducted using DFT cooperating with statistical methods, such as machine learning techniques, the kinetic Monte Carlo method, and microkinetic modeling. Large-scale calculation methods that reduce the computational cost of DFT have been proposed to treat the complex materials. In this chapter, we summarize the basic concepts of the quantum mechanics calculations (ab initio molecular orbital calculations and first-principles DFT calculations) and then introduce examples of multi-scale calculations using DFT for defects, surfaces, and interfaces and large-scale DFT calculations.