Relationship between structure and optical properties of lithium triborate

Measurements of the optical rotation of LiB₃O₅ have been carried out using a high-accuracy universal polarimeter in the temperature range 298-503 K. The results have been analyzed within the framework of a point-dipole model for the optical rotation. Though the magnitude of the rotation is very small, its sign has been clearly determined and linked to the crystallographic structure. A slight modification of the point-dipole model also permits an explanation of the values of the second-order susceptibility coefficients for second-harmonic generation.