Restoring the density-gradient expansion for exchange in solids and surfaces

Understand

Successful modern generalized gradient approximations (GGA's) are biased toward atomic energies.

• Restoration of the first-principles gradient expansion for exchange over a wide range of density gradients eliminates this bias.
• We introduce PBEsol, a revised Perdew-Burke-Ernzerhof GGA that improves equilibrium properties of densely-packed solids and their surfaces.