  Systematic studies of the two high-temperature monolayer oxygen structures
that exist on the (110) tungsten surface were performed using low-energy
electron microscopy and diffraction measurements. Our work questions the
commonly accepted interpretation from the literature that striped oxygen
superstructures arise from alternating site-exchanged (S-E) domains. We
postulate that the superstructures originate from a misfit between tungsten and
oxygen lattices while the striped appearance corresponds to a moir\'e pattern.
Moreover, we show that the two structures, indicated as 113- and 337-phases due
to the characteristic directions of the respective moir\'e patterns, differ
considerably in their symmetry properties. This suggests that oxygen atoms in
the two overlayers occupy different adsorption sites on average. In particular,
the 113-phase features rotational domains that retain mirror symmetries with
respect to the [001] and [1-10] directions, whereas the 337-phase is
characterized by the appearance of additional domains due to the breaking of
these symmetries. We propose structural models for both phases that
consistently explain their unusual properties and suggest a universal mechanism
for the thermal evolution of oxygen monolayer adsorbed on W(110).
