Correlation energies of light atoms related to pairing between antiparallel spinelectrons

Abstract

Early theoretical work emphasized the gross trend of thetotal correlation energy of neutral atoms with atomic numberZ. Thiswas later improved quantitatively, by focusing on the number of pairings betweenantiparallel-spin electrons in the same main shell (i.e., K, L, M...shells).Here, this viewpoint is pressed, and correlation energies associated with s–s, s–pand p–p pairings are extracted. The s–s energy turns out to be rather insensitiveto a change from K to L shells, but a small increase is found to occur in the Mshell. Also, the s–p and p–p pairing energies show a small increase from the L tothe M shells. The s–s and s–p energies are ≈1 eV, thes–s contribution being the larger. The p–p energy is ≈1/3 eV.The effect of removing or adding one electron to the neutral atom has also beenanalysed. Wavefunction overlap and wavefunction localization appear to controlthe values of the pairing energies.