Beyond DFT Methods

Density functional theory (DFT) has provided a practical approach to calculate and predict the electronic structure of atoms, molecules and solids. It has been known to have revolutionized the computational quantum mechanics by offering a remarkable balance between the computational efficiency and predictive power by reducing the many-body problem to one with effective single-particle periodic potential. However, its applicability is limited by its inability to capture the dynamics and many-body effects in materials displaying strong electronic-correlation effects. Subsequently, due to its static nature, it is found to fail in describing the observed electronic excitation properties of solids. These broad limitations have necessitated to resort to methods that extend beyond DFT. Some of the methods like time-dependent density functional theory (TDDFT), DFT+U, GW, and Hybrid functionals were developed and have been known to explain numerous physical properties of wide variety of solids. There are few other methods such as DFT+DMFT, GW+DMFT, which belong to recent theoretical advancements in the direction of beyond DFT methods. However, we will restrict our discussion to TDDFT, DFT+U, GW, and Hybrid functionals.