Quantum Chemical Calculation of NMR for Tetramethylsilane (TMS)

The chemical shift δ is the most important parameter in analyzing NMR spectra. It is the relative value of the sample's shielding (σ-) related to the reference's shielding (σ-ref). The reference (standard) is usually tetramethylsilane (TMS) for 1H and 13C. In quantum chemistry ab initio calculation, it is necessary to calculate the absolute shielding (σref), which has been calculated by different levels of theory and methods. The calculated results are fundamentally consistent with the experimental values.