Embedded cluster density approximation for exchange-correlation energy

We have developed a local correlation method in the framework of Kohn-Sham density functional theory (KS-DFT). The method is termed embedded cluster density approximation (ECDA), which is a logical extension of the local density approximation. In ECDA, an embedded cluster is defined for each atom, and the cluster’s exchange-correlation (XC) energy density is calculated using advanced, orbital-based XC functionals. System's XC energy is then constructed by patching these locally computed, high-level XC energy densities in an atom-by-atom manner. An efficient approach for calculating XC potential is derived, ,making ECDA a fully self-consistent method for studying charge reorganization in heterogeneous materials. ECDA is a variational method, and analytical forces are derived. To further reduce the cost of ECDA, we showed that environments can be treated using orbital-free DFT. Numerical tests show that ECDA can be applied to various systems that have different types of bonds. ECDA is a nearly "black-box" method, and we expect it to be a simple, yet effective method to scale up high-level KS-DFT calculations in large systems.