THE JAHN-TELLER INSTABILITY OF FIVEFOLD DEGENERATE STATES IN ICOSAHEDRAL MOLECULES

The linear H ⊗;(g ⊕ 2h) Jahn-Teller problem, relevant to the instability of icosahedral molecules in fivefold degenerate states, is analyzed in detail for the first time. The method of the isostationary function is used to identify all the extrema of the corresponding potential energy surface. Depending on one single mode-splitting parameter, two different coupling regimes are possible, favoring either pentagonal or trigonal minima. The saddle points on interconversion paths between equivalent minima are identified and the topology of the low-energy regions of the surface is determined. The results are found to be in agreement with the epikernel principle. In addition the symmetry characteristics of the principal warping term under the SO(5) symmetry group of electronic space are assigned. © 1990 American Institute of Physics.