Toward coupled-cluster accuracy in the prediction of nuclear shielding constants: a simple and efficient DFT approach

Exchange correlation functionals determined from energy criteria are not optimal for nuclear shielding predictions. We Ž . present a simple but highly efficient density functional theory DFT method which appears to correct for deficiencies in the Ž . virtual Kohn–Sham KS orbitals and eigenvalues. Our approach involves calculating the shieldings within the generalised gradient approximation using KS eigenvalues and orbitals from a conventional hybrid functional calculation including about 5% exact Hartree–Fock exchange. The shielding parameters produced by these new functionals on first and second-row nuclei provide a dramatic improvement over conventional DFT functionals with an accuracy approaching coupled-cluster quality. q 1999 Elsevier Science B.V. All rights reserved.