The first bismuth borate oxyiodide, BiBOI: commensurate or incommensurate?

The first bismuth borate oxyiodide, BiBOI, has been prepared by solid-state reaction in evacuated silica ampoules. Its crystal structure [space group Immm(00γ)000] comprises litharge-related layers of edge-sharing OBi tetrahedra; the interlayer space is filled by I and [BO] anions. The wavevector, q = 0.