Why the generalized gradient approximation works and how to go beyond it
✍ Scribed by Kieron Burke; John P. Perdew; Matthias Ernzerhof
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 181 KB
- Volume
- 61
- Category
- Article
- ISSN
- 0020-7608
No coin nor oath required. For personal study only.
✦ Synopsis
Ž
. The local spin density LSD approximation, while of only moderate accuracy, has proven extremely reliable over three decades of use. We argue that any gradient-corrected functional should preserve the correct features of LSD, even if the system under study Ž . contains no regions of small density gradient. The Perdew᎐Wang 1991 PW91 functional Ž . respects this condition, while, e.g., the Lee᎐Yang᎐Parr LYP correlation functional violates it. We extend this idea to the next generation of density functionals, those which Ž . incorporate exact exchange via the optimized effective potential OEP , with a model in which the correlation hole is constructed from the exact exchange hole. The resulting exchange-correlation hole is deeper and less diffuse than the exact exchange hole. We denote such a functional as ''locally correlated Hartree᎐Fock'' and list a variety of conditions such a functional should satisfy. We demonstrate the promise of this approach with a crude simple model.