SEARCH Articles Figures Tables Adiabatic generalized gradient approximations Density functional generalized gradient approximation Density functional theory generalized gradient approximation Density generalized-gradient approximation Exchange-correlation energy generalized gradient approximation Exchange-correlation functional generalized gradient approximation Functional Generalized Gradient Approximation General approximation General gradient approximation Generalized Approximations Generalized gradient approximation (GGA Generalized gradient approximation Becke Generalized gradient approximation GGA), exchange-correlation Generalized gradient approximation Perdew Generalized gradient approximation application Generalized gradient approximation asymptotic corrections Generalized gradient approximation cluster calculations Generalized gradient approximation correlation wave functions Generalized gradient approximation energy Generalized gradient approximation exchange-correlation Generalized gradient approximation generalization Generalized gradient approximation local hybrid Generalized gradient approximation methods Generalized gradient approximation relativistic form Generalized gradient approximations GGAs) Generalized gradient approximations exchange correlation functionals Gradient approximation generalization History of Several Generalized Gradient Approximations Meta-Generalized gradient approximation Perdew-Wang 1991 generalized-gradient approximation Relativistic generalized gradient approximation The Generalized Gradient Approximation