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Category:Exchange-correlation functionals

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In the KS formulation of DFT[1][2], the total energy is given by

where the terms on the right-hand side represent the non-interacting kinetic energy of the electrons, the electrons-nuclei attraction energy, the classical Coulomb electron-electron repulsive energy, the exchange-correlation energy and the nuclei-nuclei repulsion energy, respectively. The orbitals and the electron density that are used to evaluate are obtained by solving self-consistently the KS equations

The only terms in and in the KS equations that are not known exactly are the exchange-correlation energy functional and potential . Therefore, the accuracy of the calculated properties depends mainly on the approximations used for and . Several hundreds of approximations for the exchange and correlation have been proposed[3]. They can be classified into several types, like the local density approximation (LDA), generalized gradient approximation (GGA), meta-GGA, and hybrid. Functionals that include van der Waals corrections have also been proposed. More details on the different types of approximations available in VASP and how to use them can be found in the pages and subcategories listed below.

How to