Superconductivity of TiNCl intercalated with diamines

Superconducting nitride halides MNX (M = Ti, Zr, Hf; X = Cl, Br, I)

“…All distances and angles remain nearly the same as in TiNCl (see Table 7), only the basal spacing increases tremendously from 780 to 1351 pm (see Table 4). In agreement with their volumes, other TiNCl samples intercalated with organic molecules show smaller increases in basal spacing (1112 pm for EDA and 1166 pm for HDA) [9] (see Table 5). The estimated orientation of the pyridine molecules in TiNCl is therefore perpendicular to the …”

“…[139]. Other successful intercalation experiments followed for a-HfNBr [44] and even a-TiNCl with various alkali metals and organic compounds [8,9,114]. Electron-doping with lithium (also a co-intercalated phase with THF) and Na(THF) in a-HfNBr did not lead to superconducting compounds [44].…”

“…[8,9], expanding earlier results in the intercalation chemistry with the same host [114]. In order to achieve this task, TiNCl was exposed to pyridine or ethylene diamine vapour in a volumetric apparatus equipped with a pressure transducer.…”

“…While for the intercalated hafnium representatives the lattice parameters and the basal spacings are known, only the basal spacings were reported for the zirconium representatives. Thus, we are focussing our comments on the titanium representatives, for which detailed crystal structure refinements were recently reported [8,9].…”

“…The vast majority of studies so far deal with intercalates of the b-polymorphs, especially with the nitride chlorides, but more recent reports focus also on intercalates of the apolymorphs [8,9]. Since superconductivity of all these materials can not be explained with the BCS theory [10], it is still a valuable and vivid scientific field as it contributes to the quest of generating a general theory for the mechanism of superconductivity.…”