INFRARED VIBRATIONAL INTENSITIES, DIPOLE DERIVATIVES, AND CHARGE FLUX PARAMETERS FOR BF3, CO32-, AND NO3-

The infrared bands ν2 ν3, and ν4 have been measured in oblique reflectance experiments with single crystals of CaCO3 and NaNO3 having the calcite structure. The observations were made with several different polarizations, and the bands were analyzed in terms of a damped harmonic oscillator model of the anisotropic dielectric function. From the parameters of the dielectric function, the molecular dipole derivatives, ∂μ/∂qk, k = 2, 3, 4, were calculated making appropriate corrections for the difference between the internal and external electric fields. These derivatives (along with the corresponding ones from published data for 11BF3) were transformed to derivatives, with respect to internal symmetry coordinates. In order to accomplish this transformation for modes 3 and 4, a molecular potential function must be available: we have carefully analyzed the uncertainties in the ∂μ/∂Sk, values which arise in consequence of imprecise definition of the potential function. Finally, the data are reduced to atomic effective charges and charge fluxes, utilizing simple bonding theory to facilitate the choice of some of the indeterminate signs of the ∂μ/∂qk which arise because (∂μ/∂qk)2 is the measurable quantity in most studies. © 1979 American Chemical Society.