An $ab$ $initio$ CASSCF study of Zero Field Splitting Fluctuations in the Octet Ground State of Aqueous [Gd(III)(HPDO3A)(H$_2$O)]

Shehryar Khan (1) , Rodolphe Pollet (2) , Rodolphe Vuilleumier (3) , Jozef Kowalewski (4) , Michael Odelius (1)

1 Department of Physics [Stockholm]
2 LSDRM - Laboratoire Structure et Dynamique par Résonance Magnétique (LCF)
3 PASTEUR - Processus d'Activation Sélective par Transfert d'Energie Uni-électronique ou Radiatif (UMR 8640)
4 Arrhenius Laboratory

In this work we present $ab$ $initio$ calculations of the zero-field splitting (ZFS) of a gadolinium complex[Gd(III)(HPDO3A)(H$_2$O)] sampled from an ab initio molecular dynamics (AIMD) simulation. We perform both post-Hartree-Fock (complete active space self-consistent field - CASSCF)and density functional theory (DFT) calculations of the ZFS and compare and contrast the methods with experimental data. Two different density functional approximations (TPSS and LC-BLYP) were investigated. The magnitude of the ZFS from the CASSCF calculations is in good agreement with experiment, whereas the DFT results in varying degree overestimate the magnitude of the ZFS for both functionals and exhibit a strong functional dependence. It was found in the sampling over the ab initio molecular dynamics (AIMD) trajectory that the fluctuations in the transient ZFS tensor derived from DFT is not correlated with that of CASSCF, nor does the magnitude of the ZFS from CASSCF and DFT correlate. From the fluctuations in the ZFS tensor, we extract a correlation time of the transient ZFS which is on the sub-picosecond time scale, showing a faster decay than experimental estimates.

Domaines: Matériaux

Shehryar Khan, Rodolphe Pollet, Rodolphe Vuilleumier, Jozef Kowalewski, Michael Odelius. An $ab$ $initio$ CASSCF study of Zero Field Splitting Fluctuations in the Octet Ground State of Aqueous [Gd(III)(HPDO3A)(H$_2$O)]. Journal of Chemical Physics, 2017, 147, pp.244306. ⟨10.1063/1.5010347⟩. ⟨cea-01675442⟩