DIFFRACTION LINE-PROFILE OF A 2-DIMENSIONAL HEXATIC

The structure factor is calculated for the Nelson and Halperin model o f the hexatic phase as a two-dimensional crystal containing a gas of i nteracting dislocations. It is shown that the diffraction peaks are Ga ussians in the azimuthal direction. The azimuthal and the radial peak widths are expressed in terms of the elastic moduli and the mean dislo cation density and do not involve any phenomenological parameter. The ratio of the radial to the azimuthal peak widths decreases considerabl y when the dislocations interact and depends on the sample size.