VWN parameterization

The LDA correlation functional used in these calculations was not the VWN parameterization of the Ceperly and Alder reference data for the uniform electron gas but that of Perdew and Wang.18... 

The analytical form for the correlation energy of a uniform electron gas, which is purely dynamical correlation, has been derived in the high and low density limits. For intermediate densities, the correlation energy has been determined to a high precision by quantum Monte Carlo methods (Section 4.16). In order to use these results in DFT calculations, it is desirable to have a suitable analytic interpolation formula, and such formulas have been constructed by Vosko, Wilk and Nusair (VWN) and by Perdew and Wang (PW), and are considered to be accurate fits. The VWN parameterization is given in eq. (6.36), where a slightly different spin-polarization function has been used. 

The first DFT calculations on GC and AT base pairs recently appeared. Calculations were carried out within the LSDA using the VWN parameterization. Calculations beyond the LSDA were also performed using Becke s gradient-corrected exchange functionaP and Perdew s gradient-corrected correlation functional. The results from these calculations are listed in Tables 6 and 7, along with those from HF and MP2 calculations. ... 

They studied N2 as a test case, and used several large basis sets including the TZVP basis set augmented with field induced polarization functions, and the Sadlej basis. They use LDA with the VWN parameterization, and the calculations were carried out with their dMon suite of programs. The Cauchy moments are calculated directly from SOS formulae. 

However, extended parameterization of the local correlation energy may be unfolded since considering the fit with an LSDA p and p ) ana-l>4ical expression by Vosko, Wilk andNusair (VWN) (Vosko et al., 1980),... 

LDA (S-VWN) Perdew-Zunger parameterization Local density approximation... 

LDA takes its densities from the uniform electron gas (UEG), and an analytical form of a density functional for the exchange energy of the UEG can be derived (the same exchange energy as used in the HFS-method). No such expression exists for the correlation energy, but the UEG correlation energy can be calculated numerically and lit in various ways. One successfid and popular parameterization comes from the work of Vosko, Wilk, and Nussair, referred to as VWN (Vosko et al. 1980). 

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