3He NMR: from free gas to its encapsulation in fullerene

The He-3 nuclear magnetic shieldings were calculated for single helium atom, its dimer, simple models of fullerene cages (He@C-n), and single wall carbon nanotubes. The performances of several levels of theory (HF, MP2, DFT-VSXC, CCSD, CCSD(T), and CCSDT) were tested. Two sets of polarization-consistent basis sets were used (pcS-n and aug-pcS-n), and an estimate of He-3 nuclear magnetic shieldings in the complete basis set limit using a two-parameter fit was established. Theoretical He-3 results reproduced accurately previously reported theoretical values for helium gas, dimer, and helium probe inside several fullerene cages. Excellent agreement with experimental values was achieved. He-3 nuclear magnetic shieldings of single helium atom approaching various points of benzene ring were tested, and an impact of He-3 confinement within fullerene cages of different size on the He-3 chemical shift was determined. Copyright (c) 2013 John Wiley & Sons, Ltd.