The ampule showed signs of attack during the growth reaction determined by XRD to be cristobalite (SiO 2 ), a feature not uncommon in CVT reactions using Cl 2 as a transport agent. It is important to note that neither hard X-ray photoelectron spectroscopy (HAXPES) surveys (Figure ) nor energydispersive X-ray spectroscopy (EDS) measurements (Figure ) showed any silicon in the crystals.