The temperature dependent shear strain of the (NbSe4)(10)I-3 compound, a quasi-one-dimensional charge density wave system, below the Peierls transition

An X-ray study of the quasi-one-dimensional charge density wave (CDW) system (NbSe4)(10)I-3 as a function of temperature from room temperature down to 130 K has been performed by taking oscillation and zeroth level Weissenberg photographs. A reversible transformation of the room temperature tetragonal lattice into four symmetrically-relate monoclinic domains has been observed at the Peierls transition temperature, T-p approximate to 285 K, with a continuous change of the monoclinic angle from 90 degrees to 92.1 degrees at 130 K. The monoclinic deformation of the tetragonal lattice, i.e. the shear-strain along the chain axis seems to be an elastic response to the long wavelength transverse modulation of the 3D-CDW order which can be qualitatively explained by taking into account the Coulomb interaction between CDWs on neighbouring chains up to the next-nearest-neighbours