Showing papers by "Robert Berger published in 2000"

Electroweak quantum chemistry of alanine: parity violation in gas and condensed phases.

Abstract: Just how different are the energies of left- and right-handed alanine enantiomers because of parity violation? Substantial advances in electroweak quantum chemistry have provided new answers to this question. The present, advanced calculations lead to the conclusion that numerous previous claims of L-alanine stabilization by parity violation are unjustified. This introduces some extra pepper into current discussions of the origin of biomolecular homochirality. The picture shows a zwitterionic model with conformational changes and solvent effects, as included in the calculations.

Multiconfiguration linear response approach to the calculation of parity violating potentials in polyatomic molecules

Abstract: We present a multiconfiguration linear response approach to electroweak quantum chemistry including effects from the parity violating weak nuclear force. Compared to our previous configuration interaction singles-restricted Hartree–Fock (CIS-RHF) approach [A. Bakasov, T. K. Ha, and M. Quack, J. Chem. Phys. 109, 7263 (1998)], the parity violating potential Epv is introduced by the linear response function and by solving the linear response equations in a direct iterative manner. Calculations are carried out within the multiconfiguration linear response approximation (MCLR) and its special cases, the configuration interaction approach (CI) and the random phase approximation (RPA). The systematic approach presented here, provides a systematic check and improvement upon various approximations used in the calculation of Epv. Extensive results are obtained for hydrogen peroxide at the CISDT (CI singles, doubles and triples) and CISDTQ (CI singles, doubles, triples, and quadruples) as well as at the complete act...