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 H 2 O 2 and H 2 S 2 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