Thin films of hafnium oxides deposited by atomic layer deposition are usually crystalline. It is isomorphous to transition metal tetrachlorides of zirconium, hafnium, and platinum. These TPS materials are based on zirconium diboride and hafnium diboride. In contrast, the trihalides of the heavier metals hafnium and zirconium engage in metal-metal bonding. It contains the elements titanium (Ti), zirconium (Zr), hafnium (Hf) and rutherfordium (Rf). Hafnium and tantalum isomers can be induced to emit very strong gamma radiation. The foremost use of corrosion-resistant hafnium and zirconium has been in nuclear reactors. Albany calls itself the "rare metals capital of the world", producing zirconium, hafnium and titanium. About half of all hafnium metal manufactured is produced as a by-product of zirconium refinement. These results may imply that dubnium behaves more like hafnium than niobium. This process for differential purification of zirconium and hafnium is still in use today. The production of hafnium-free zirconium is the main source for hafnium. Francium was the last element discovered in nature, rather than synthesized, following hafnium and rhenium. Perhaps the simplest hafnium metallocene is halfnocene dichloride.