Hybrid functionals screened

For the VCD studies described in Sects. 4.1 and 4.2, the B3LYP hybrid functional [83, 84] was used because of its proven reliability in predicting VCD intensities [25, 85, 86] and in describing strong H-bonded complexes [87-89], The initial screening calculations were carried out at a low level of theory such as HF/3-21G or B3LYP/6-31G [90, 91]. The final geometry optimizations of the chiral molecular systems were performed with 6-311++G(d,p) or aug-cc-pVTZ [92],... 

Hybrid functionals other than B3LYP have also proved successful in localised orbital methods. Yang and Dolg found that the hybrid functional B3PW including spin-orbit coupling reproduced the band gap of BiB30g well, while Prodan et u/." found that the HSE (Heyd, Scuseria and Emzerhof) screened coulomb hybrid potential described the oxides of uranium and plutonium well. The performance of hybrid functionals is discussed by Cora et Just as there is no universal... 

Recently, Heyd et al. [262] used the screening of 1/m to adapt global hybrid functionals to calculations of periodic systems with small band gaps. Such an adaptation is necessary because direct evaluation of exact exchange in periodic systems with metallic character is prohibitively expensive, rendering conventional hybrids utterly impractical for many solids. Heyd et al. start with rewriting the one-parameter global hybrid functional of Eq. (187) as... 

In 2003, Heyd et al. proposed to use a screened Coulomb operator in the Hartree-Fock exchange part of hybrid functionals [41]. The Coulomb operator was split into short-range (SR) and long-range (LR) components. 

The important advantage of the Scuseria-Kudin implementation of the DFT LCAO 0 N) method for solids is the possibility to use hybrid HF-DFT exchange-correlation functionals, including the recently developed screened Coulomb hybrid functional, discussed in the next subsection. 

Heyd-Scuseria-Ernzerhof Screened Coulomb Hybrid Functional... 

Screened Coulomb hybrid functionals do not need to rely on the decay of the density matrix to allow calculations in extended systems [409]. The SR HF exchange interactions decay rapidly and without noticeable dependence on the bandgap of the system. The screening techniques do not rely on any truncation radius and provide much better control over the accuracy of a given calculation. In addition, the thresholds can be set very tightly, without resulting in extremely long alculations. 

Fig. 13. Near-Fenni-energy structure of the hybridization function for the asymmetric PAM. The model parameters are 17 = 1.5, F = 0.6 and n, = 1. The dip at the Fermi energy denotes a decrease in the number of states available for screening, leading to a suppressed coherence Kondo scale T. The zero ten erature hybridization for the single-impurity Anderson model is shown for comparison.

Heyd, J., 8c Scuseria, G. E. (2004). Efficient hybrid density functional calctdations in solids Assessment of the Heyd-Scuseria-Ernzerhof screened Coulomb hybrid functional. The Journal of Chemical Physics, 121,1187-1192. 

Peralta, J. E., Heyd, J., Scuseria, G. E., 8c Martin, R. L. (2006). Spin-orbit splittings and energy band gaps calculated with the Heyd-Scuseria-Ernzerhof screened hybrid functional. Physical Review B, 74, 073101. 

J. Heyd, G. E. Scuseria, and M. Ernzerhof,/. Chem. Phys., 118, 8207-8215 (2003). Hybrid Functionals Based on a Screened Coulomb Potential. 

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