Modeling the Neutral-Ionic Transition with Correlated Electrons Coupled to Soft Lattices and Molecules
Institut Néel, CNRS and Grenoble Alpes University, F-38042 Grenoble, France
Department of Chemistry, Life Science and Environmental Sustainability, Università di Parma, 43100 Parma, Italy
Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
Author to whom correspondence should be addressed.
Academic Editors: Anna Painelli and Alberto Girlando
Received: 3 April 2017 / Revised: 2 May 2017 / Accepted: 7 May 2017 / Published: 16 May 2017
Neutral-ionic transitions (NITs) occur in organic charge-transfer (CT) crystals of planar
-electron donors (D) and acceptors (A) that form mixed stacks ... D+ρ
... with variable ionicity
and electron transfer t
along the stack. The microscopic NIT model presented here combines a modified Hubbard model for strongly correlated electrons delocalized along the stack with Coulomb intermolecular interactions treated in mean field. It also accounts for linear coupling of electrons to a harmonic molecular vibration and to the Peierls phonon. This simple framework captures the observed complexity of NITs with continuous and discontinuous ρ
on cooling or under pressure, together with the stack’s instability to dimerization. The interplay of charge, molecular and lattice degrees of freedom at NIT amplifies the nonlinearity of responses, accounts for the dielectric anomaly, and generates strongly anharmonic potential energy surfaces (PES). Dynamics on the ground state PES address vibrational spectra using time correlation functions. When extended to the excited state PES, the NIT model describes the early (<1 ps) dynamics of transient NIT induced by optical CT excitation with a fs pulse. Although phenomenological, the model parameters are broadly consistent with density functional calculations.
This is an open access article distributed under the Creative Commons Attribution License
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).
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MDPI and ACS Style
D’Avino, G.; Painelli, A.; Soos, Z.G. Modeling the Neutral-Ionic Transition with Correlated Electrons Coupled to Soft Lattices and Molecules. Crystals 2017, 7, 144.
D’Avino G, Painelli A, Soos ZG. Modeling the Neutral-Ionic Transition with Correlated Electrons Coupled to Soft Lattices and Molecules. Crystals. 2017; 7(5):144.
D’Avino, Gabriele; Painelli, Anna; Soos, Zoltán G. 2017. "Modeling the Neutral-Ionic Transition with Correlated Electrons Coupled to Soft Lattices and Molecules." Crystals 7, no. 5: 144.
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