Neutral-ionic interface in organic charge-transfer salts

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Abstract

Charge transfer (CT) stabilization in linear stacks D+A-D+A- of -electron donors (D) and acceptors (A) involve spin-dependent configuration interactions that are treated exactly in rings of N=4, 6, 8, 10 sites, and extrapolated to N, by adapting valence-bond techniques to electron-hole excitations. The ground state CT (z) and the magnetic gap Em(z)2|t| to the lowest triplet are computed for arbitrary z=2|t|, where -2 is the energy for DAD+A-, -|t|=D+A-|H|DA is the Mulliken CT integral, and D2+, A2- sites are excluded. The spin degeneracy of A- and D+ ion radicals is treated exactly. Instead of the discontinuous change from =0 to =1 in the limit |t|0, finite overlap gives a continuous (z) and (zc)=0.680.01 at the neutral-ionic interface zc=0.530.01. The magnetic gap Em is finite for z<zc and vanishes for z>zc, where there is a diamagnetic to paramagnetic transition and the ground state switches from k=0 to k= symmetry. Collective effects due to long-range three-dimensional Coulomb interactions are included in a Hartree approximation and produce a first-order transition, with discontinuous (z), when the critical value m2|t|=1.40.1 of the Madelung stabilization m of a dimer is exceeded. The puzzling magnetic gaps in paramagnetic organic CT salts with mixed regular stacks arise naturally for partial CT and z<zc. Valence-bond analysis of CT excitations models the physical properties of organic complexes with overlapping sites and intermediate.

Original languageEnglish (US)
Pages (from-to)1991-2003
Number of pages13
JournalPhysical Review B
Volume18
Issue number4
DOIs
StatePublished - 1978
Externally publishedYes

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organic charge transfer salts
Charge transfer
Salts
charge transfer
Ground state
stabilization
valence
Stabilization
Hartree approximation
ground state
Electrons
configuration interaction
excitation
Electron transitions
Coulomb interactions
Dimers
switches
physical properties
dimers
Physical properties

ASJC Scopus subject areas

  • Condensed Matter Physics

Cite this

Neutral-ionic interface in organic charge-transfer salts. / Soos, Z. G.; Mazumdar, Sumitendra.

In: Physical Review B, Vol. 18, No. 4, 1978, p. 1991-2003.

Research output: Contribution to journalArticle

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