title: Magnetic properties with multiwavelets and DFT: the complete basis set limit achieved.
abstract: Multiwavelets are emerging as an attractive alternative to traditional basis sets such as Gaussian-type orbitals and plane waves. One of their distinctive properties is the ability to reach the basis set limit (often a chimera for traditional approaches) reliably and consistently by fixing the desired precision ε. We present our multiwavelet implementation of the linear response formalism, applied to static magnetic properties, at the self-consistent field level of theory (both for Hartree-Fock and density functional theories). We demonstrate that the multiwavelets consistently improve the accuracy of the results when increasing the desired precision, yielding results that have four to five digits precision, thus providing a very useful benchmark which could otherwise only be estimated by extrapolation methods. Our results show that magnetizabilities obtained with the augmented quadruple-ζ basis (aug-cc-pCVQZ) are practically at the basis set limit, whereas absolute nuclear magnetic resonance shielding tensors are more challenging: even by making use of a standard extrapolation method, the accuracy is not substantially improved. In contrast, our results provide a benchmark that: (1) confirms the validity of the extrapolation ansatz; (2) can be used as a reference to achieve a property-specific extrapolation scheme, thus providing a means to obtain much better extrapolated results; (3) allows us to separate functional-specific errors from basis-set ones and thus to assess the level of cancellation between basis set and functional errors often exploited in density functional theory.
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway. stig.r.jensen@uit.no kenneth.ruud@uit.no.
authors.forename: Stig Rune
authors.initials: SR
authors.lastname: Jensen
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway. stig.r.jensen@uit.no kenneth.ruud@uit.no and Department of Mathematics and Statistics, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway.
authors.forename: Tor
authors.initials: T
authors.lastname: Flå
authors.affiliation: High-Performance Computing Group, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway.
authors.forename: Dan
authors.initials: D
authors.lastname: Jonsson
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway. stig.r.jensen@uit.no kenneth.ruud@uit.no.
authors.forename: Rune Sørland
authors.initials: RS
authors.lastname: Monstad
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway. stig.r.jensen@uit.no kenneth.ruud@uit.no.
authors.forename: Kenneth
authors.initials: K
authors.lastname: Ruud
authors.affiliation: Centre for Theoretical and Computational Chemistry, Department of Chemistry, University of Tromsø - The Arctic University of Norway, N-9037 Tromsø, Norway. stig.r.jensen@uit.no kenneth.ruud@uit.no.
authors.forename: Luca
authors.initials: L
authors.lastname: Frediani