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.
@article{arxiv.0711.0156,
title = {Restoring the density-gradient expansion for exchange in solids and surfaces},
author = {John P. Perdew and Adrienn Ruzsinszky and Gabor I. Csonka and Oleg A. Vydrov and Gustavo E. Scuseria and Lucian A. Constantin and Xiaolan Zhou and Kieron Burke},
journal= {arXiv preprint arXiv:0711.0156},
year = {2008}
}