Performance of modern density functional theory for the prediction of hyperfine structure: meta-GGA and double hybrid functionals

Abstract

. Performance of modern density functional theory for the prediction of hyperfine structure: meta-GGA and double hybrid functionals. Molecular Physics, Taylor & Francis, 2008, 105 (15-16) AbstractThe performance of modern density functionals for the prediction of molecular hyperfine couplings is investigated for a series of small radicals and transition metal complexes. Besides the established BP86 (GGA) and B3LYP (hybrid) functionals we have tested two prototypical members of emerging classes of density functionals, namely the TPSS meta-GGA functional (together with its hybrid version TPSSh) and the B2PLYP double-hybrid functional. The latter is the first member of a 'fifth-rung' density functional that incorporates a fraction of orbital dependent nonlocal correlation energy estimated at the level of second order many-body perturbation theory. Since this approach is non-variational, it becomes necessary to derive and implement the so-called 'relaxed' densities in order to properly predict hyperfine couplings. The necessary formalism is described in some detail and the new method has been implemented into the ORCA electronic structure program. The results of extended test calculations reveal that TPSS is superior to BP86. The hybrid variant TPSSh is at least as accurate or better than the B3LYP functional and significantly superior to the nonhybrid TPSS variant. The B2PLYP functional also leads to accurate predictions and is a clear improvement for the difficult metal nucleus HFCs. However, it also showed a few significant outliers in the test set which points to a somewhat reduced stability in the method. The latter effect is largely attributed to the elevated fraction Hartree-Fock exchange (53%) and to some extent also to the perturbative correction.

Copper impurities in bulk ZnO: A hybrid density functional study

“…This is found to be essential for the quantitative reproduction of experimental values in the case of transition metal compounds and in particular for Cu 2+ complexes. 50,51 Although largely underestimated, the computed dipolar components make up the major part of the hyperfine coupling constants, in line with the fact that the unpaired electron lies mostly in a d orbital.…”

Role of zero-point vibrational corrections to carbon hyperfine coupling constants in organic π radicals

“…One such relation is the McConnell relation that states that the spin density ρ C on the carbon of a C-H fragment in an organic π radical is linearly dependent on the isotropic hyperfine constant of hydrogen. [1][2][3] Although such relations or structure-property tools have frequently been used in the field of EPR, [4][5][6] recent advances in the quantum chemical modeling of HFCCs in organic radicals [7][8][9][10][11][12][13][14][15][16][17][18] offer an alternative way for exploring the physical origin of these constants.…”

“…[7][8][9][10][11][12][13][14][15][16][17][18] The lack of such analysis tools forced early investigations of EPR data to rely on rules-of-thumb or simple principles that relate the spin density to the measured hyperfine coupling constants (HFCCs). One such relation is the McConnell relation that states that the spin density ρ C on the carbon of a C-H fragment in an organic π radical is linearly dependent on the isotropic hyperfine constant of hydrogen.…”

Hyperfine Coupling Constants from Internally Contracted Multireference Perturbation Theory

“…[13][14][15][16] Yet another approach is based on density functional theory (DFT). 10,[17][18][19][20][21] These approaches have been generalized to relativistic analogues to account for the scalar relativistic and spin-orbit effects. [22][23][24][25][26] Recently, Lan et al 27,28 has used the CASSCF method with the density-matrix renormalization group (DMRG) algorithm to show that it is capable of reproducing experimental results when used with very large active spaces (up to 36 orbitals).…”