Abstract
The incommensurate charge-density waves (CDW’s) in the phosphate bronze have been studied by synchrotron-radiation x-ray scattering. The CDW is found to correspond to a state for all temperatures below the first phase transition at The second phase transition at is found to involve the development of mixed second-order satellites within the primary CDW. The incommensurately modulated structure has been determined at The structure remains orthorhombic down to At 20 K the lattice parameters are and The two-dimensional CDW is characterized by the modulation wave vectors and The superspace group was found as The primary CDW comprises the satellite reflections with equal to and Below additional satellite reflections develop, that correspond to Accordingly, harmonic modulation amplitudes (1,0), (0,1), and were incorporated into the structure model. Refinement against 4970 observed reflection intensities resulted in a fit with The periodic lattice distortion shows that the CDW is located at the centers of the slabs. The CDW is interpreted in terms of the formation of clusters of six tungsten atoms, that are linked together to form larger clusters of 12 to 18 atoms.
- Received 14 September 2000
DOI:https://doi.org/10.1103/PhysRevB.64.104105
©2001 American Physical Society