Ab initio 13C shielding parameters in acetylene clusters

Abstract The coupled Hartree—Fock method has been used to calculate ab initio carbon magnetic shielding tensors for small clusters of acetylene molecules. The chemical shift increases from the monomer to the dimer and the trimer. This is mainly due to increased diamagnetism, which is imperfectly cancelled by increased paramagnetism due to loss of axial symmetry. Anisotropic effects are shown to be small in both the dimer and the trimer.