The structure of a monolayer film of carbon dioxide adsorbed on graphite

The structure of a monolayer film of CO2 on graphite has been determined by X-ray diffraction. The 2-dimensional space group is pgg and the rectangular unit cell has lattice parameters a = 0·439 nm and b = 0·693 nm at 120 K. There are two molecules in the unit cell, arranged in a herringbone structure and aligned at angles of + and -41° with respect to the short side of the cell.