Why spin contamination is a major problem in the calculation of spin-spin coupling in triplet biradicals.
In organic triplet biradicals, zero field splitting is dominated by the spin-dipolar interaction. While it has been observed before that spin-unrestricted density functional calculations give huge errors for systems with small D values, a consistent explanation was still missing. Using model systems, this work demonstrates how spin contamination creates unphysical one-center terms in the two-particle density matrix that spoil the calculated results.
Fachbereich Chemie and Forschungszentrum OPTIMAS, Technische Universität Kaiserslautern, 67663 Kaiserslautern, Germany. christoph.vanwullen@chemie.uni-kl.de.
Patrick
P
Jost
Christoph
C
van Wüllen