Evaluation of model exchange-correlation kernels in the adiabatic connection fluctuation-dissipation theorem for inhomogeneous systems.

Abstract

We investigated the effect of the exchange-correlation kernels of Dobson and Wang (DW) [Phys. Rev. B 62, 10038 (2000)] and Corradini, Del Sole, Onida, and Palummo (CDOP) [Phys. Rev. B 57, 14569 (1998)] in the framework of the adiabatic connection fluctuation-dissipation theorem. The original CDOP kernel was generalized to treat inhomogeneous systems, and an efficient numerical implementation was developed. We found that both kernels improve the correlation energy in bulk silicon as compared to that evaluated from the random phase approximation (RPA). In particular, the correlation energy from the CDOP kernel is in excellent agreement with the diffusion Monte Carlo result. In the case of the Kr dimer, while the DW kernel leads to stronger binding than RPA, the CDOP kernel does the opposite. The cause of this quite different behavior of the two kernels is discussed. Our study suggests that special attention needs to be paid to describe the effective interaction at the low density regions when developing model exchange-correlation kernels.