Structural model of the (1 x 4) reconstructed surface. Upper panel: side view, lower panel: top view. The ball-and-stick model sketches three kinds of ridges. Left: the ADM ridge (O TOP-ADM ), right: the AOM ridge (O TOP-AOM ), middle: the mixed ADM and AOM ridge with a ratio of 1:1. The O TOP , O SIDE , O TERRACE , and O BULK atoms are correspondingly colored in upper and lower panels. An O TOP-AOM becomes an O TOP-ADM when it is missing an O atom marked by the red arrows. The surface O V defects at terrace (O V-TERRACE and O V-3C ) and ridge (O V-RIDGE ) sites are marked by the black arrows.
