Breit interaction contribution to parity violating potentials in chiral molecules containing light nuclei

The importance of the Breit interaction for an accurate prediction of parity violating energy differences between enantiomers is studied within electroweak quantum chemical frameworks. Besides two-electron orbit-orbit and spin-spin coupling contributions, the Breit interaction gives rise to the spin-other-orbit coupling term of the Breit-Pauli Hamiltonian. The present numerical study demonstrates that neglect of this latter term leads in hydrogen peroxide (H2O2) to relative deviations in the parity violating potential (V-pv) by about 10%, whereas further relativistic corrections accounted for within a four-component Dirac-Hartree-Fock-Coulomb (DHFC) framework remain smaller, below 5%. Thus, the main source of discrepancy between previous one-component based (coupled perturbed) Hartree-Fock (HF) and four-component Dirac-Hartree-Fock results for parity violating potentials in H2O2 is the neglect of the Breit contribution in DHFC. In heavier homologs of hydrogen peroxide the relative contribution of the spin-other-orbit coupling term to V-pv decreases with increasing nuclear charge, whereas other relativistic effects become increasingly important. As shown for the H2X2 (X=O,S,Se,Te,Po) series of molecules and for CHBrClF, to a good approximation these other relativistic influences on V-pv can be accounted for in one-component based HF calculations with the help of relativistic enhancement factors proposed earlier in the theory of atomic parity violation. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.2958280]