Abstract
Low-temperature X-ray diffraction with synchrotron radiation was used to study the CDW structure of the phosphate bronze (PO2)4(WO3)2m with m = 4. The CDW state at T = 20 K can be described as a 2-dimensional, incommensurately modulated structure with wave vectors q1 = (0.330(5),0.292(5),0) and q2 = ( − 0.330,0.292,0). The second type of modulation is found to comprise the mixed second-order satellites q1 − q2 at (0.340(5),0,0). Atomic displacements are mainly found on the wolfram atoms, whereby a tendency is observed for the CDW to concentrate in the middle of the WO3 layers. The consequences are derived for the interpretation of the CDW modulations in this homologous series of compounds.