Structure and the nonlinearity of lithium triborate studied by Raman and infrared reflectivity spectroscopy

Raman and infrared measurements of the LiB3O5 (LBO) crystals were completed . The experimental results shown here are more and stronger Raman lines and infrared absorption peaks. which implies that the external vibrations of t he trigonal (BO3)(3-) and tetrahedral (BO4)(5-) ions, especially the former , in the six-membered boron-oxygen rings at the low wave number are strong and the internal vibrations of the (BO4)(5-) ions above 200 cm(-1) are stro nger than those of the (BO3)(3-) ions if compared with the Raman spectra of BaB2O4 crystals. These are caused due to the slope and distortions of the B3O7 rings and their BO3 and BO4 units in LBO, which change the structural rigidity of the crystals. intensify the long-range electrostatic force and short-range molecular force, and shorten the ultraviolet absorption edge.