Quantum chemical predictions of the properties of known and postulated neutral interstellar molecules

In order to make new predictions for chemical rate coefficients for ion-molecule reactions, quantum chemical calculations were performed for about 200 neutral molecules with up to 12 atoms that are known or postulated to be present in interstellar or circumstellar sources. After optimizing equilibrium structures, dipole moment and dipole polarizability components were computed using the finite field approach. Properties were computed at the RCCSD(T) level with basis sets as large as aug-cc-pVTZ, depending upon the size of the molecule. Comparisons are made to existing experimental data, which are quite limited in the case of dipole polarizabilities.