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Tungsten trioxide adopts a variety of structures which can be intercalatedwith charged species to alter the electronic properties, thus forming `tungstenbronzes'. Similar optical effects are observed upon removing oxygen from WO_3,although the electronic properties are slightly different. Here we present acomputational study of cubic and hexagonal alkali bronzes and examine theeffects on cell size and band structure as the size of the intercalated ion isincreased. With the exception of hydrogen (which is predicted to be unstable asan intercalate), the behaviour of the bronzes are relatively consistent. NaWO_3is the most stable of the cubic systems, although in the hexagonal system thelarger ions are more stable. The band structures are identical, with theintercalated atom donating its single electron to the tungsten 5d valence band.Next, this was extended to a study of fractional doping in the Na_xWO_3 system(0 < x < 1). A linear variation in cell parameter, and a systematic change inthe position of the Fermi level up into the valence band was observed withincreasing x. In the underdoped WO_3-x system however, the Fermi levelundergoes a sudden jump into the conduction band at around x = 0.2. Lastly,three compounds of a layered WO_4&#215;a,wdiaminoalkane hybrid series werestudied and found to be insulating, with features in the band structure similarto those of the parent WO_3 compound which relate well to experimentalUV-visible spectroscopy results.Comment: 12 pages, 16 figure

Density-functional studies of tungsten trioxide, tungsten bronzes, and related systems