Attempts to construct a better functional in the generalized gradient approximation (GGA) face a trade-off. Functionals with an enhanced gradient dependence improve atomization and total energies, but worsen bond lengths. Some suggestions of a GGA for solids have a reduced gradient dependence and typically do improve lattice parameters and/or surface energies, but have been criticized for worsening total and atomization energies. No GGA can do both: Accurate atomic exchange energies require violating the gradient expansion for slowly-varying densities, which is valid for solids and their surfaces .