Perdew-Wang exchange functional

GGA functionals satisfy the uniform density limit. In addition, they satisfy several known, exact properties of the exchange-correlation hole. Two widely used nonempirical functionals that satisfy these properties are the Perdew-Wang (PW) functional [15] and the Perdew-Burke-Emzerhof (PBE) functional [16]. Because GGA functionals include more physical ingredients than the LDA functional, it is often assumed that GGA functionals should be more accurate than the LDA. This is quite often true, but there are exceptions. One example of such a situation is in the calculation of the surface energy of transition metals and oxides. 

Fig. 5. Calculated structure and NMR parameters of 5 (8( Si) and 5( C) at DFPT/IGLO/Basis III//B3LYP/ 6-3IG using the Perdew Wang exchange correlation functional (IMS

Perdew and Wang have proposed an exchange functional similar to B88 to be used in connection with the PW91 correlation functional given below (eq. (6.30)). 

Functionals which are related to this approach include among others the recent FT97 functional of Filatov and Thiel, 1997, the PW91 exchange functional (Perdew, 1991, and Burke, Perdew, and Wang, 1998) and the CAM(A) and CAM(B) functionals developed by Handy and coworkers (Laming, Termath, and Handy, 1993). 

In Ref. [12], Perdew and Burke made a graphical comparison of various GGA s. The popular functionals for exchange (Perdew-Wang 86 [8], Becke 88... 

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