Geometries force constants and harmonic frequencies are calculated for the cyclic (dioxirane) structure of CO3 by ab initio SCF methods using the 3-21G, 3-21G(*). 6-31G and 6-31G* bases calculated frequency shifts for isotopomeric species agree with experiment and lend support to the vibrational assignments of Jacox and Milligan. Earlier arguments for and against the cyclic, cyclic and open structures of CO3, based upon the "physical reasonableness" of valence force constants are shown to be invalid owing to the dependence of conventional "rigid" force constants upon the choice of valence coordinates. The use of "relaxed" force constants as a basis for meaningful comparison of force fields for molecules described by different sets of redundant valence coordinates is demonstrated.
ASJC Scopus subject areas
- Physics and Astronomy(all)
- Physical and Theoretical Chemistry