Use of the complete basis set limit for computing highly accurate ab initio dipole moments.

Calculating dipole moments with high-order basis sets is generally only possible for the light molecules, such as water. A simple, yet highly effective strategy of obtaining high-order dipoles with small, computationally less expensive basis sets is described. Using the finite field method for computing dipoles, energies calculated with small basis sets can be extrapolated to produce dipoles that are comparable to those obtained in high order calculations. The method reduces computational resources by approximately 50% (allowing the calculation of reliable dipole moments for larger molecules) and simultaneously improves the agreement with experimentally measured infrared transition intensities. For atmospherically important molecules, which are typically too large to consider the use of large basis sets, this procedure will provide the necessary means of improving calculated spectral intensities by several percent.