the green atom is bonded to tungsten (6+) in pentagonal bipyramid and the cyan atom to two tungsten atoms (5+). In fact, though one should distinguish between two groups of oxygen atoms. This grouping is evident in the DFT calculation of the ELNES spectrum of the oxygen K edge (Figure ). The blue, yellow and orange oxygen atoms could be further divided into subgroups. However, to minimize the complexity of the presentation they are represented each by one color. Nonetheless, their heterogeneity (second nearest neighbors) is manifested by the broadness of their calculated ELNES band-like spectrum (Figure ). In sharp contrast, the green, cyan, and red curves are narrow reflecting the minor heterogeneity of the oxygen atoms bound to W 5+ atoms.