Direct Observation of Discommensuration Arrays in NbTe4by Means of Low-Temperature Electron Microscopy

Abstract
The pseudo one-dimensional compound NbTe4 exhibits a lock-in-type phase transition around 50 K. Electron microscopy reveals the occurrence of discommensurations; their evolution as a function of temperature is reported. A microstructure model is proposed in which cooperative dephasing between one-dimensional Nb-string segments generates the discommensurations. An alternative description using concepts currently applied for long-period antiphase-boundary structures provides a valid description for the phenomena observed below room temperature.