Transferability of nonbonded Cl...Cl potential energy function to crystalline chlorine

The crystal structure of molecular chlorine could not be accurately predicted using a transferred nonbonded Cl^...Cl potential function that was found satisfactory for prediction of perchlorohydrocarbon crystal structures. Additional consideration of quadrupole-quadrupole interaction did not resolve this problem. One possible solution, which has been explored in the literature, was to define a new, nontransferable, Cl^...Cl potential function specifically tailored to molecular chlorine. Such a specialized Cl^...Cl function required additional adjustable parameters that defined an anisotropic nonbonded energy function for chlorine. A second possible approach, explored here, transferred the perchlorohydrocarbon Cl^...Cl potential function to molecular chlorine. This simple isotropic nonbonded energy function was then supplemented by a partial intermolecular bonding force constant, which was applied to the short contacts present in this structure type. The resulting empirical model described the crystal structure of molecular chlorine within threshold accuracy.