Chemical structures of the three protoplanetary disk models. The left panels are for the reference model (R), the middle panels are for the gas-poor gap model (A), and the right panels are for the gas-rich gap model (B). Different species are shown in the top and bottom halves of each panel. D in H is the total number of D atoms in H isotopologues. The location of the gap is shown as a hatched background. The gas isotherms of 20 and 40 K are shown in blue and red in the upper panels, respectively, highlighting the CO snowline location and shape.