RelativisticAb InitioTheory using the Regular Approximation

Abstract

AbstractAn account of the theoretical methods for atomic and molecular calculations in anab initiorelativistic quantum‐mechanical framework, based on the regular approximation to the exact formalism, is presented. A brief introduction into the nature of relativistic effects and into the full four‐component relativistic quantum‐mechanical formalism is given. A classification of the quasirelativistic methods including the methods based on the Foldy–Wouthuysen transformation of the Dirac equation is presented. The concept of the regular approximation to the exact relativistic formalism is introduced. Theab initiomethods within the regular approximation ranging from the zeroth‐order regular approximation (ZORA) to the infinite‐order regular approximation (IORA) methods are described and details of their implementation are discussed. A brief survey of the results of theab initiocalculations on atomic and molecular systems concludes the account.