Coupling constants intrachain

Figure 10 Evidence for one-dimensional ferromagnetic correlations in PbMnB04. Note the positive deviation from the horizontal xT = C line with decreasing temperature. The inset shows a fit to Fisher s model for a linear ferromagnet with S = 2 J/ks = -1-11 K is found for the intrachain coupling constant. (Reprinted with permission from Ref. 17, 2003 American Chemical Society)...

Here n and Ep are the bare density of states and the Fermi energy, X is the electron-phonon coupling constant and Uq is the intrachain Coulomb interaction. When the interchain coupling is weak... 

As discussed by Travers [102], this can be due to either (1) an increase in the intrachain diffusion rate or (2) a decrease in the electron-proton coupling constants. In case 1, hydration has an effect on the polaron mobility, i.e., the latter is enhanced in case 2, hydration modifies the polaron electronic wave function. In addition, T p shows that the low frequency contribution to the proton relaxation is not affected, which is not consistent with a change in the coupling constant. It can be concluded that the increase in the macroscopic conductivity observed on hydration is related to an increase of the on-chain polaron mobility. A possible explanation can be proposed in terms of a solvation effect of the counterions resulting in a depinning of the polarons. 

When the involved transition metal possesses eg electrons, the interchain constant J2 is greater than the intrachain constant J3. This result is due to stronger 135° M-F-M superexchange interactions (occuring via eg-pcr-eg antiparallel couplings) which are... 

Fortunately, TTF-TCNQ is a particularly suitable prototype, because of the amenability of the TTF donor molecule to chemical modification. Some of the possibilities are illustrated in Figure 1. Any or all of the sulfur heteroatoms can be replaced with selenium, and the terminal protons can be replaced with any of a wide variety of substituent groups. To study the role of interchain coupling, we seek to hold the molecular electronic structure and intrachain stacking patterns as nearly constant as possible, while introducing steric factors chosen so as to force changes in the crystal structure. 

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