Density exchange-correlation functionals

The applicability of the local spin density exchange-correlation functional. This is of very great concern for localized f orbitals. Harmon (1979) noted that the calculated minority f character in Gd was falling too low in energy and it does appear that there is too much minority f occupation in all subsequent calculations. 

The total electron density is just the sum of the densities for the two types of electron. The exchange-correlation functional is typically different for the two cases, leading to a set of spin-polarised Kohn-Sham equations ... 

There is no systematic way in which the exchange correlation functional Vxc[F] can be systematically improved in standard HF-LCAO theory, we can improve on the model by increasing the accuracy of the basis set, doing configuration interaction or MPn calculations. What we have to do in density functional theory is to start from a model for which there is an exact solution, and this model is the uniform electron gas. Parr and Yang (1989) write... 

Adamo, C., Ernzerhof, M., Scuseria, G. E., 2000, The meta-GGA Functional Thermochemistry with a Kinetic Energy Density Dependent Exchange-Correlation Functional , J. Chem. Phys., 112, 2643. 

Becke, A. D., 1996b, Current-Density Dependent Exchange-Correlation Functionals , Can. J. Chem., 74, 995. 

Table 4.1. Acronyms used in text for parametrizations for the exchange-correlation (Exc) functional. The acronyms for separate exchange (Ej and correlation (E ) components of A xc are specified when applicable. Throughout the text, density functional calculations following the Kohn-Sham formalism are referred to as DFT(XXX), where XXX stands either for the acronym of the approximate exchange-correlation functional or for the acronyms of the exchange and correlation functionals, separated by the / symbol.

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