Magnetisabilities in density functional theory

Abstract

A new approach, denoted MKS (Multiplicative Kohn–Sham), has recently been used [Chem. Phys. Lett., 337 (2001) 341] to determine NMR shielding constants directly from theoretical electron densities. In the present study, we investigate the applicability of the MKS approach to the determination of isotropic and anisotropic magnetisabilities. We consider HF, H 2O, CH 4, CO, N 2, F 2, O 3, NH 3, HCN, C 2H 2, H 2CO, and CO 2. MKS magnetisabilities are calculated by determining the multiplicative Kohn–Sham potential associated with a theoretical electron density, and using the associated Kohn–Sham orbitals and eigenvalues in the standard uncoupled magnetisability expression. Compared to correlated wavefunction-based results, the quality of the MKS magnetisabilities improves as the electron density is varied from Hartree–Fock to MP2 to Brueckner Doubles. The best agreement with correlated results is obtained when Kohn–Sham densities are used, determined from a hybrid exchange-correlation functional. These MKS magnetisabilities are an improvement over conventional Kohn–Sham values.