The structure of CS2 adsorbed on graphite

The structure of an adsorbed layer of CS 2 on graphite has been determined by X-ray diffraction. The experimentally determined unit cell has lattice parameters a = 0·807 nm, b = 0·602 nm, and β = 90°. There are two molecules in the unit cell arranged in a herringbone structure and aligned at angles of + and -33° with respect to the short side of the unit cell. The structure has also been calculated using a three centre interaction site model and different quadrupolar interactions. The favoured configuration of the isolated molecule was found to be with the carbon atom over a saddlepoint and the two sulphurs in the centre of adjacent hexagons. However, the most favourable structure for the whole layer was found to be incommensurate. Two stable structures were found whose relative energies depended on the value chosen for the quadrupole moment, θ. One of them, where θ has the value 11 × 10 -40 C m 2 , is close to the experimental structure, with lattice parameters a = 0·785 nm, b = 0·625 nm, and β = 90°, and two molecules per unit cell inclined at angles of + and -29° to the shorter side.