The dynamical correlation in spacer-mediated electron transfer couplings

摘要

The dynamical correlation effect in electron transfer (ET) coupling was studied in this work,for cases where electrons tunnel through a many-electron environment.The ET couplings for three different bridge-mediated model systems were calculated:(I) trans-alkyl chains [H_2C-(CH_2)_n-CH_2,n=2-10],(II) two isomers of trans-1,4-dimethylenecyclohexane,and (III) two ethylenes spaced by a saturated ethane molecule.The couplings were calculated as half energy gaps of the two lowest adiabatic states.The dynamical correlation was included with spin-flip (SF) and ionization potential or electron affinity coupled-cluster singles and doubles (SF-CCSD and IP/EA-CCSD) and a DELTA CCSD scheme.The direct coupling (DC) scheme is also used as a way to obtain a solution with nondynamical correlation,since DC uses approximated eigenstates that are symmetry-restoring linear combinations of two symmetry-broken unrestricted Hartree-Fock configurations.For all cases tested except for one,results from the DC scheme closely follow the CCSD data,indicating that the dual-configuration solutions can be a good approximation of wave functions with nondynamical correlation included,but there exist exceptions.Comparing the DC results with SF-CCSD and IP or EA-CCSD data,we concluded that the dynamical correlation effect is small for most of the cases we tested.