Ab initio calculation of parity-violating potential energy hypersurfaces of chiral molecules ^†

We introduce the explicit concept of parity-violating potential energy hypersurfaces which govern the rotation–vibration tunneling dynamics as well as the time-dependent parity violation in chiral molecules. Calculations are reported for sections of the hypersurfaces of H₂O₂ and H₂S₂ at various levels of electroweak quantum chemistry, including CIS-RHF, CIS-LR, and CASSCF-LR. Important findings concern the observed increase of the parity-violating potentials (E_pv) with increasing bond lengths r_OO and r_SS, which is to some extent physical and partly a consequence of the only approximate electronic wavefunction and perturbational treatment, the confirmation of lines and surfaces of “accidentally” zero E_pv at chiral geometries, and the absence of a precise, simple scaling law for observables such as the measurable parity-violating energy difference between enantiomers ΔE_pv. The latter is due to the complicated geometry dependent E_pv, although a rough scaling on the order of Z^(5±1) with nuclear charges of the two heavy centers can be confirmed. The results are discussed in relation to possible experiments on molecular parity violation. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004