Abstract Incommensurate structures of barium adatoms on the Mo(110) face are studied by the LEED method. A splitting of fractional-order beams corresponding to a commensurate c(2 × 2) barium structure is observed upon the commensurate-incommensurate transition. This result agrees with a model predicting the formation of linear solitons (domain walls) in the c(2 × 2) phase. A change of the soliton inner structure is found with increasing barium coverage. From the temperature dependence of the splitting it is inferred that with a rise in temperature a part of the excessive adatoms (with respect to the c(2 × 2) phase) goes from the solitons into the domains of this phase and forms interstitials. Frozen surface defects (preadsorbed oxygen atoms) are found to influence significantly both the ground state and the dynamical properties of the incommensurate barium phase.