Crystal growth, crystal structure, vibrational spectroscopy, linear and nonlinear optical properties of guanidinium phosphates

Abstract Of the three guanidinium phosphates GuH 2 PO 4 (space group P 2 1 / c ), Gu 2 HPO 4 ·H 2 O (space group P 4 ¯ 2 1 c ) and Gu 3 PO 4 ·  3 2 H 2 O (space group Cc ) crystal structures and a vibrational spectroscopy study are presented. Large single crystals of GuH 2 PO 4 and Gu 2 HPO 4 ·H 2 O are grown. Refractive indices and their dispersion in the wavelength range 365 nm – 1083 nm are determined and used for the analysis of phase matching conditions for collinear SHG in the case of the non-centrosymmetric crystals of Gu 2 HPO 4 ·H 2 O. The crystals are not phase-matchable within their transmission range. Both independent components of the SHG tensor of Gu 2 HPO 4 ·H 2 O, determined by the Maker fringe method, are given, with d 14  = 0.23 pm/V and d 36  = 0.22 pm/V. In addition, the thermal stability and the anisotropy of thermal expansion of GuH 2 PO 4 and Gu 2 HPO 4 ·H 2 O is reported.