Comparative Density Functional Theory Study of Magnetic Exchange Couplings in Dinuclear Transition-Metal Complexes

Multicenter transition-metal complexes (MCTMs) with magneticallyinteracting ions have been proposed as components for information-processingdevices and storage units. For any practical application of MCTMsas magnetic units, it is crucial to characterize their magnetic behavior,and in particular, the isotropic magnetic exchange coupling, J, between its magnetic centers. Due to the large size oftypical MCTMs, density functional theory is the only practical electronicstructure method for evaluating the J coupling. Here,we assess the accuracy of different density functional approximationsfor predicting the magnetic couplings of eight dinuclear transition-metalcomplexes, including five dimanganese, two dicopper, and one divanadiumwith known reliable experimental J couplings spanningfrom ferromagnetic to strong antiferromagnetic. The density functionalsconsidered include global hybrid functionals which mix semilocal densityfunctional approximations and exact exchange with a fixed admixingparameter, six local hybrid functionals where the admixing parametersare extended to be spatially dependent, the SCAN and r (2)SCAN meta-generalized gradient approximations (GGAs),and two widely used GGAs. We found that global hybrids tested in thiswork have a tendency to over-correct the error in magnetic couplingparameters from the Perdew-Burke-Ernzerhof (PBE) GGAas seen for manganese complexes. The performance of local hybrid densityfunctionals shows no improvement in terms of bias and is scatteredwithout a clear trend, suggesting that more efforts are needed forthe extension from global to local hybrid density functionals forthis particular property. The SCAN and r (2)SCAN meta-GGAs are found to perform as well as benchmarkglobal hybrids on most tested complexes. We further analyze the chargedensity redistribution of meta-GGAs as well as globaland local hybrid density functionals with respect to that of PBE,in connection to the self-interaction error or delocalization error.