Force-torque correlations

The equilibrium force-torque correlation ?Nf? is studied, first for a general fluid in which the intermolecular potential is expanded in generalized spherical harmonics, and then for the specific case of homonuclear diatomic molecules. If coordinate axes are taken with z axis parallel to the 12 intermolecular vector, it is shown that two (and only two) elements of the tensor are non-zero : ?n_x (12)f_y (12)? = -?n_y (12)f_x (12)?. For the linear molecule, these elements are evaluated in the limit of zero density for the atom-atom model of the potential. Example calculations are done, numerically for finite L (where L is the length of the diatomic molecule) and analytically in the limit of small L.