The exchange-correlation functional used. The exchange-correlation functional used in a given simulation. Available values for this are: LDA, the Local Density Approximation PW91, Perdew and Wang's 1991 formulation PBE, Perdew, Burke and Enzerhof's original GGA functional RPBE, Hammer et al's revised PBE functional /cml:cml/cml:parameterList[@dictRef="input"]/cml:parameter[@dictRef="castep:xcFunctional"] XC_FUNCTIONAL convertibleToInput value absolute input LDA PW91 PBE RPBE 2 parameterInInput [ [ , ], ] ] .//cml:lattice