Effect of Anion Disorder on the Peierls Transition in the Commensurate One-Dimensional Conductors (TTF)(SCN)_0.56(ClO₄)_0.01, (TTF)(NO₃)_0.59(Cl)_0.28, and (TTF)(SCN)_0.09(Br)_0.59

Abstract

Three new quasi-one-dimensional tetrathiafulvalenium (TTF) conductors, (TTF)(SCN)0.56(ClO4)0.01, (TTF)(NO3)0.59(Cl)0.28, and (TTF)(SCN)0.09(Br)0.59, were obtained by electrochemical crystallization. They are all nonstoichiometric compounds with commensurate anion ratios and behave as Mott's 1D variable range hopping conductors because of their disordered anion structure. Evidenced by their unusual structure−conductivity characteristics, they are considered as in the intermediate regime, ranging from the highly conducting incommensurate compounds to the almost insulating commensurate salts with Peierls structure typified by (TTF)3(BF4)2. The Peierls instability is thus suppressed giving incomplete Peierls structures for these compounds despite their commensurate band filling ratio. This was most probably derived from the random potential exerted over TTF conducting chain by the disordered anion structure.

Preparation, structure and conduction properties of SeCN-containing mixed anion TTF conductors

“…The crystal structure was analyzed for the seven of the currently identified 21 mixed anion TTF conductors. They were (TTF)(Cl) 0.42 (ClO 4 ) 0.14 , 12 (TTF)(Cl) 0.60 (BF 4 ) 0.02 , 13 (TTF)(Cl) 0.66 (SCN) 0.09 , 13 (TTF)(Cl) 0.28 (NO 3 ) 0.59 , 16 (TTF)(SC-N) 0.47 (NO 3 ) 0.10 , 15 (TTF)(SCN) 0.12 (Cl) 0.57 , and (TTF)(Se-CN) 0.26 (Cl) 0.43 . All of them have a tetragonal lattice and space group P4 2 /mnm and are isostructural to each other except (TTF)(Cl) 0.28 (NO 3 ) 0.59 , which has an orthorhombic lattice and space group Pnnm.…”

“…The effect of the disorder on the Peierls 19 instability was reported in more detail in our previous article on mixed anion commensurate salts. 16…”