Directly Patching Exchange-Correlation Energy in Density Functional Theory

Kohn-Sham density functional theory is widely used nowadays for large-scale material simulations, however its accuracy is limited by the accuracy of the exchange-correlation (XC) functionals. We will discuss our effort on developing the exchange-correlation energy patching (XCEP) method in which for each atom (called central atom) we select its nearby atoms as its buffer atoms. The central atom and its buffer atoms form the cluster. The rest atoms form the environment. The system’s electron density is then partitioned among the cluster and environment using the finite-temperature density functional embedding theory developed recently in our group. The obtained cluster is a small KS system, whose XC energy density can be computed using a high-level XC functional. The system’s XC energy is constructed by patching these high-level, local XC energy densities over the entire system in an atom-by-atom manner. The performance of XCEP is investigated by patching the random phase approximation correlation energy in some one-dimensional systems, and by patching the exact exchange energy in molecules. We show that by increasing the clusters’ sizes the XCEP results converge to the benchmarks.