Equilibrium geometries of cyclic SiC3 isomers

Equilibrium geometries of two isomers of cyclic SiC3 are determined by both large scale ab initio calculation and a procedure involving the use of exp erimental data from microwave spectroscopy and calculated harmonic and cubi c force fields. Internuclear distances corresponding to structures obtained by both procedures agree to better than 0.003 Angstrom in all cases, allow ing for precise recommendations of equilibrium structures. Rather large res idual inertial defects obtained from moments of inertia based on rotational constants adjusted for effects of vibration-rotation interaction were foun d to be reduced significantly by inclusion of electronic contributions as e stimated from calculations of rotational g-tensors. (C) 2001 American Insti tute of Physics.