Modeling the (13)C chemical-shift tensor in organic single crystals by quantum mechanical methods: finite basis set effects.

The influence of using finite basis sets to calculate (13)C magnetic shieldings were explored using the Hartree-Fock and the B3LYP hybrid density functional methods. The shielding values were compared in a linear least-squares fashion for a test group of 102 (13)C complete chemical-shift tensors determined from 14 organic single crystals. Pople's basis sets allow for the addition of polarization and diffuse functions in a straightforward way, allowing the examination of 81 combinations at the double and triple zeta level.