Bond-breaking excitations with diverging coupling matrix of response density functional theory from highest-level functionals★
Computational Molecular Science Research Team, RIKEN Advanced Institute for Computational Science,
2 Section Theoretical Chemistry, VU University, Amsterdam, The Netherlands
a e-mail: firstname.lastname@example.org
Received in final form: 13 April 2018
Published online: 18 June 2018
Bond-breaking excitations ωα are the problematic case of adiabatic time-dependent density functional theory (TDDFT). The calculated ωα erroneously vanishes with the bond elongation, since the Hartree-exchange-correlation kernel and the corresponding response coupling matrix K of standard approximations lack the characteristic divergence in the dissociation limit. In this paper an approximation for K is proposed constructed from the highest-level functionals, in which both occupied and virtual Kohn-Sham orbitals participate with the weights wp. The latter provide the correct divergence of K in the limit of dissociating two-electron bond. The present K brings a decisive contribution to the energy of the 1Σu+ in the prototype H2 molecule calculated for various H-H separations. At shorter separations it improves ωα compared to the zero-order TDDFT estimate, while at the largest separation it reproduces near-saturation of the reference excitation energy.
© EDP Sciences / Società Italiana di Fisica / Springer-Verlag GmbH Germany, part of Springer Nature, 2018
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