Correlation in a relativistic framework
Abstract
By the use of projection operators, defined in Dirac space, it is shown how a relativistic pair equation, correct to order α ^{2}Ry, can be constructed. It is pointed out how the BrownRavenhall disease (continuum dissolution) is rigorously avoided with this procedure. The pair equation treats correlation relativistically starting from a suitable choice of a fully relativistic oneparticle description of the atom. Second order contributions to the energy from the electrostatic correlation have been calculated for the 1s ^{2} ground state of some twobody systems. The starting point has been either hydrogenlike wave functions ( Z = 2, 10) or DiracFock orbitals ( ^{Z} 1060). Excitations to s ^{2}, p ^{2}, d ^{2} and f ^{2} have been treated and an unexpected behaviour of the p^{2}_{{1}/{2}} excita P^{2}_{{3}/{2}} one is discussed. By iterative solutions of the exact pair equation a nonperturbative treatment of the twobody part of the s Coulomb interaction is obtained. This procedure has been used for s excitations ( Z = 220) and a comparison of the relativistic and nonrelativistic behaviour is made.
 Publication:

Nuclear Instruments and Methods in Physics Research B
 Pub Date:
 July 1987
 DOI:
 10.1016/0168583X(87)900905
 Bibcode:
 1987NIMPB..27..543L