*From*: Bernd Engels <bernd[ AT ]rs5.thch.uni-bonn.de>*Subject*: Summary Symmetry-breaking*Date*: Mon, 9 Aug 1999 09:09:35 +0200 (MES)

Summary: Symmetry-breaking effects My original question was: > > dear ccl'er > > I looking for examples of the symmetry breaking effect. > As described in a paper of Davidson and Borden (JPC, 87 (1983) 3063) > it is the effect that the electronic wavefunctions has a lower > symmetry than the nuclear framework. An example is the > allyl radical with an ROHF type wave function, where > the nuclear framework has C2v symmetry but the C2v > wave function corresponds to a (first order) saddle point. > I am looking for more examples and some newer references. > I also know a reference from Cederbaum and coworker in Mol.Phys. > but I don't know the exact reference. > > I am not interested in the problem that ab initio > programms are not able to handle the full symmetry > but uses abelian subgroups. > > Thank you in advance and I will summarize > > Bernd Engels > Inst. für Org. Chemie > Universität Würzburg > Thanks to all who responded: Here is the summary: Well, these are starting to get a bit old, but we found a number of dioxophosphoranyl radicals to exhibit HF doublet instability. See, for instance Cramer, C. J.; Famini, G. R. "Computational Studies of Open-Shell Phosphorus Oxyacids 1. P-H Bond Homolysis in H2PO2" J. Am. Chem. Soc. 1990, 112, 5460. Cramer, C. J.; Lim, M. H. "Efficient Prediction of Isotropic Hyperfine Coupling in Radicals Containing Phosphorus. A Systematic Comparison of UHF, PUHF, and UMP2 Spin Densities" J. Phys. Chem. 1994, 98, 5024. Best regards, Chris Christopher J. Cramer University of Minnesota Department of Chemistry 207 Pleasant St. SE Minneapolis, MN 55455-0431 -------------------------- Phone: (612) 624-0859 || FAX: (612) 626-2006 cramer[ AT ]pollux.chem.umn.edu http://pollux.chem.umn.edu/~cramer a simpler case might be the n=2 wavefunction for an electron in 3 linear boxes separated by barriers V= infinity 0 0 < x < 1 constant 1 < x < 1.5 0 1.5 < x < 2.5 constant 2.5 < x < 3 0 3 < x < 3.5 infinity which is a simple undergrad or grad-level pen-and-paper exercise Kieran ------------------------------------------------------------ Dr Kieran F Lim Biol. and Chemical Sciences (Lim Pak Kwan) Deakin University ph: + [61] (3) 5227-2146 Geelong VIC 3217 fax: + [61] (3) 5227-1040 AUSTRALIA mailto:lim[ AT ]deakin.edu.au http://www.deakin.edu.au/~lim Dear Bernd, You might try the following references to get you into the literature on symmetry breaking examples. HCOO ...... McLean at al. J.Chem.Phys. 1985, 83,1459. Linear carbon clusters Liang and Schaefer III Chem.Phys. Lett. 1990,169,150. FC(O)O...... Schneider, Marieq and Francisco, J.Chem.Phys. 1995, 103, 6601 NO3 ....... Kim et al. Chem.Phys.Lett. 1990, 168, 131. Regards, Graham Chandler