Away from generalized gradient approximation: Orbital-dependent exchange-correlation functionals

Deorbitalization strategies for meta-generalized-gradient-approximation exchange-correlation functionals

We explore the simplification of widely used meta-generalized-gradient approximation (mGGA) exchangecorrelation functionals to the Laplacian level of refinement by use of approximate kinetic-energy density functionals (KEDFs). Such deorbitalization is motivated by the prospect of reducing computational cost while recovering a strictly Kohn-Sham local potential framework (rather than the usual g...

Functional derivatives of meta-generalized gradient approximation (meta-GGA) type exchange-correlation density functionals.

Meta-generalized gradient approximation (meta-GGA) exchange-correlation density functionals depend on the Kohn-Sham (KS) orbitals through the kinetic energy density. The KS orbitals in turn depend functionally on the electron density. However, the functional dependence of the KS orbitals is indirect, i.e., not given by an explicit expression, and the computation of analytic functional derivativ...

Electron Correlation in Orbital Dependent Functionals

Generalized-gradient-approximation noninteracting free-energy functionals for orbital-free density functional calculations

We develop a framework for orbital-free generalized gradient approximations (GGAs) for the noninteracting free energy density and its components (kinetic energy, entropy) based upon analysis of the corresponding gradient expansion. From that we obtain a new finite-temperature GGA (ftGGA) pair. We discuss implementation of the finite-temperature Thomas-Fermi, second-order gradient expansion, and...

Avoiding singularity problems associated with meta-GGA (generalized gradient approximation) exchange and correlation functionals containing the kinetic energy density.

Convergence problems of meta-GGA (generalized gradient approximation) XC (exchange and correlation) functionals containing a self-interaction correction term are traced back to a singularity of the latter that occurs at critical points of the electron density. This is demonstrated for the bond critical point of equilibrium and stretched H2. A simple remedy is suggested that cures meta-XC functi...