Chemical approach to neutral–ionic valence instability, quantum phase transition, and relaxor ferroelectricity in organic charge-transfer complexes

Phenomenology of the Neutral-Ionic Valence Instability in Mixed Stack Charge-Transfer Crystals

“…The (a) panel of Figure 15 shows that in TMB-TCNQ the TCNQ a g ν 4 mode shifts from 1418 to 1411 cm −1 at the phase transition. For a regular chain like room-temperature TMB-TCNQ we can use the trimer model to estimate ρ, and by disregarding the interaction among e-mv coupled modes (isolated band approximation), the perturbed frequency Ω is given by [49]: (8) where ω N is the vibrational frequency of the neutral molecule, ∆ the ionization frequency shift, g the e-mv coupling constant and ω CT is the frequency of the CT transition. Below the transition, when the stack is dimerized, the dimer model can be adopted [49]: (8) and (9) for the TCNQ a g ν 4 mode with the parameters given in the text.…”

Novel Countercation in MMX-Type Mixed-Valence Chain Compound: Coexistence of Neutral and Protonated Amino Substituents

“…Because these CT complexes can be obtained as single crystal, these are suitable to study the fundamentals of 1D electron system. So far, various electronic states of Q1D materials and their relationships to attractive physical properties, such as non-linearity [5,6], superconductivity [7], ferroelectricity [8] etc., have been extensively studied.…”

Crystal structure and phase transition of 2-methoxyanilinium perchlorate-18-crown-6

“…Searching for new solid-to-solid phase transitions triggered by temperature is very important not only for the exploration of novel physical properties but also theoretically for the study of structure-property relationships [1][2][3][4][5]. Recently, a series of research has been conducted on phase transitions in organic and inorganic hybrid complexes, which possess the properties of both organic and inorganic compounds [6][7][8][9].…”