Momentum-space properties of atoms: Application of the generalized-gradient approximation

The calculations of Compton profiles and various [p(n)]-expectation values are carried out for a few closed-shell atomic systems within Perdew-Burke-Emzerhof (PBE), Perdew-Wang 1991 (PW91) and Becke-Lee-Yang-Parr (BLYP) generalized-gradient approximations. The calculated Compton profiles and the moments are compared with their local-density approximation (LDA) and more accurate available theoretical or experimental counterparts in order to investigate the supremacy of generalized gradient approximation (GGA) over LDA in predicting the momentum-space properties. The results show that GGA improves the Compton profiles marginally. The PBE and PW91 values of Compton profiles are practically identical and are slightly better than BLYP. Further comparison of GGA and LDA results with those calculated within self-interaction corrected LDA (SICLDA) formalism demonstrates the importance of proper description of the valence region in the study of Compton profiles. GGA values of the moments of electron momentum density are found to be, in general, more accurate than their LDA counterparts.