Sixth-order Douglas–Kroll: two-component reference data for one-electron ions from through

Abstract

Abstract Quasirelativistic Douglas–Kroll calculations including spin–orbit interaction have been performed for hydrogen-like (one-electron) ions. The Douglas–Kroll operators have been implemented up to the sixth order, and a huge even-tempered basis set has been applied that gives results to microhartree accuracy for the energy levels 1 s 1 2 through 4 f 7 2 for all ions with nuclear charge from Z = 1 up to Z = 100. Besides providing reference data for other implementations, these results can be used to analyse the performance of the Douglas–Kroll method. Such an analysis is presented for the 1s energy levels and the spin–orbit splitting of the 2p shell. The leading order of the error of the Douglas–Kroll result is different for 2s and 2 p 1 2 although these levels are degenerate both at nonrelativistic and Dirac level.