Use of the Generalized Gradient Approximation in Pseudopotential Calculations of Solids

TL;DR

This paper investigates the application of generalized gradient approximation (GGA) functionals in pseudopotential calculations of solids, showing improved cohesive energies over LDA but underestimating bulk moduli.

Contribution

It introduces a method to incorporate GGA functionals into pseudopotential calculations and compares their effectiveness against LDA and experimental data.

Findings

GGA improves cohesive energy predictions over LDA.

Lattice constants are comparable between GGA and LDA when core-valence coupling is considered.

GGA underestimates bulk moduli compared to experimental values.

Abstract

We present a study of the equilibrium properties of $sp$-bonded solids within the pseudopotential approach, employing recently proposed generalized gradient approximation (GGA) exchange correlation functionals. We analyze the effects of the gradient corrections on the behavior of the pseudopotentials and discuss possible approaches for constructing pseudopotentials self-consistently in the context of gradient corrected functionals. The calculated equilibrium properties of solids using the GGA functionals are compared to the ones obtained through the local density approximation (LDA) and to experimental data. A significant improvement over the LDA results is achieved with the use of the GGA functionals for cohesive energies. For the lattice constant, the same accuracy as in LDA can be obtained when the nonlinear coupling between core and valence electrons introduced by the exchange correlation functionals is properly taken into account. However, GGA functionals give bulk moduli that are too small compared to experiment.