STRUCTURAL STUDY OF A CHLOROFORM FILM ADSORBED ON GRAPHITE

The structural characterization of a chloroform (CHCl3) film adsorbed on graphite was performed by means of X-ray and neutron diffraction be tween 40 and 227 K. Results are consistent with those of a previous th ermodynamic characterization and can be related to difficulties in the adsorbed film nucleation. The first layer melts at 166 K. At 227 K, t he CHCl3 bilayer spectrum is that of a liquid, in agreement with the 2 25 K melting temperature determined from the isotherm measurements. Th e diffraction profiles of solid adsorbed CHCl3 are representative of a mixture of two structures on a microscopic scale. One of them is hexa gonal with a 5.91 Angstrom parameter, and appears to be the most stabl e, the second is a square unit cell with a 5.77 Angstrom parameter. (C ) 1998 Elsevier Science B.V.