Chi-Ruei Pan, Po-Tung Fang, Jeng-Da Chai
Aiming to remedy the incorrect asymptotic behavior of conventional semilocal exchange-correlation (XC) density functionals for finite systems, we propose an asymptotic correction (AC) scheme, wherein an exchange density functional whose functional derivative has the correct (-1/r) asymptote can be directly added to any semilocal density functional. In contrast to semilocal density approximations, our resulting exchange kernel in reciprocal space exhibits the desirable singularity of the type O(-1/q^2) as q -> 0, which is a necessary feature for describing the excitonic effects in non-metallic solids. By applying this scheme to a popular semilocal density functional, PBE [J. P. Perdew, K. Burke, and M. Ernzerhof, Phys. Rev. Lett. 77, 3865 (1996)], the prediction of properties that are sensitive to the asymptote, such as the highest occupied molecular orbital energies and Rydberg excitation energies, is significantly improved, while the prediction of properties that are insensitive to the asymptote, such as reaction energies and valence excitation energies, remains essentially the same as PBE. In addition, without loss of accuracy, two closely related AC schemes are developed for the efficient treatment of large systems.
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http://arxiv.org/abs/1211.0385
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