Comparisons with crystalline solids, particularly molecular crystals, would eliminate or greatly simplify a number of these issues. The rigidity and regularity of a crystal would simplify the "solvent" environment by eliminating the need for conformational averaging. The extended structure around a molecule can be determined from the crystal structure and can be readily simulated through the use of periodic boundary conditions (PBC). In principle, solid state experiments allow the entire OR tensor to be resolved, unlike solution or gas phase where only the isotropic OR can be measured. However, linear birefringence is 2-3 orders of magnitude larger than circular birefringence. Therefore, OR measurements are typically performed along special axes (called optic axes) where linear birefringence is zero, although the experi-mental determination of the directions corresponding to these axes is difficult. Nonetheless, a direct comparison with experimental data for solids would provide complimentary information about this property that is not easily accessible for solvated systems.