What is meta-GGA?
Meta-GGA (6, 7, 10, 11) is the highest rung at the semilocal level of Jacob’s ladder of DFT, (12) which includes the kinetic energy density as an input in addition to the electron density and its density gradient.
What are XC functionals?
The Density Functional, also called the exchange-and-correlation (XC) functional, consists of an LDA, a GGA part, a Hartree-Fock exchange part (hybrids), and a meta-GGA part (meta-GGA or meta-hybrid). A hybrid GGA (for example B3LYP) stands for some combination of a standard GGA with a part of Hartree-Fock exchange.
What is PBE0 functional?
PBE0 is a hybrid functional (different class than GGA) which is based on PBE. there are important differences between hybrid exchange-correlation functionals (PBE0) and GGAs. PBE0 contains an exact-exchange contribution and GGAs do not. Thus, the effective potential imposed by these functionals is different.
What is B3lyp?
B3lyp is a functional, that includes exact exchange and GGA corrections in addition to LDA electron-electron and electron-nuclei energy. The weights of the parts were fit to reproduce geometry of a test suite of small molecules. As such use of b3lyp for calculations with heavier atoms is questionable.
What is GGA approximation?
Generalized gradient approximations (GGA’s) for the exchange-correlation energy improve upon. the local spin density (LSD) description of atoms, molecules, and solids. We present a simple. derivation of a simple GGA, in which all parameters (other than those in LSD) are fundamental. constants.
What is PBE GGA?
GGA functionals PBE (Perdew et al., 1996) is the default exchange-correlation functional. It is recommended, especially, for studies of molecules interacting with metal surfaces, although it is also fairly reliable for bulk calculations.
What is LDA and GGA?
LDA predicts stiffer bonds from which higher values of the IFCs stem; whereas GGA usually gives softer bonds and thus lower values of the IFCs. An alternative approach would be to fix the lattice parameter to the experimental value at the temperature of interest and perform the IFCs calculations as this fixed volume.
What is GGA in VASP?
Description: GGA specifies the type of generalized-gradient-approximation one wishes to use. This tag was added to perform GGA calculation with pseudopotentials generated with conventional LDA reference configurations. Possible options are: The tags AM (AM05) and PS (PBEsol) are only supported by VASP.5.X.
Can hybrid and meta-GGA functionals be implemented in the standard Kohn–Sham formalism?
However, hybrid and meta-GGA functionals are often not implemented in the standard Kohn–Sham formalism, where the Kohn–Sham potential is strictly local, since this would require using the optimized effective potential method 25, 26, 27, i.e. solving a complicated integral equation.
What is meta-GGA DFT?
A meta-GGA DFT functional in its original form includes the second derivative of the electron density (the Laplacian). This is a natural development after the GGA (generalized gradient approximation), that includes only the density and its first derivative in the exchange-correlation potential.
What are the MS functionals available in VASP?
The MS functionals are available as of VASP version ≥ 5.4.1. The modified Becke-Johnson exchange potential in combination with L (S)DA-correlation yields band gaps with an accuracy similar to hybrid functional or GW methods, but computationally less expensive (comparable to standard DFT calculations).