Positional feature: Unlike molecular graphs, the importance of each atom in the catalyst surface differs for adsorption energy prediction (Fig. ). For example, atoms at the top layers are more important, while atoms at the bottom are less important. Moreover, GNNs are unable to determine the relative heights of atoms in a surface based on a surface graph, making it impossible to distinguish between top-layer and bottom-layer atoms. To help models understand the varying importance of atoms at different relative heights (Fig. ), each atom i of a surface graph will get a positional feature δ i computed by