GRADIENT-FREE EXCHANGE-CORRELATION FUNCTIONAL BEYOND THE LOCAL-SPIN-DENSITY APPROXIMATION

The gradient-free correlation functional derived in a previous work [E . I, Proynov and D. R. Salahub, Phys. Rev. B 49, 7874 (1993)] is combi ned with two different exchange counterparts-the standard local-spin-d ensity (LSD) exchange and a modified LSD exchange derived in the spiri t of the local thermodynamic approach in density-functional theory(DFT ). These exchange-correlation schemes are tested on a set of small mol ecules. The obtained binding energies are on average comparable to tho se of the gradient-corrected ones used currently in the DFT code deMON . The equilibrium geometries produced by our functionals are superior and on average very close to the experimental ones. The required compu ter time is comparable to that of the Vosko, Wilk, and Nusair LSD sche me [Can. J. Phys. 58, 1200 (1980)].