Characteristics of structure, thermal stability and optical properties for a novel NLO crystal (C5H12NO)H2PO4

A novel organic-inorganic hybrid crystal, (C 5 H 12 NO)H 2 PO 4 (4-(Hpd)H 2 PO 4 ), has been synthesized by evaporation method under ambient atmosphere. Based on structure analysis, the compound crystalizes in the polar space group P2 1 with the parameters a = 8.6074 (6) Å, b = 6.3134 (4) Å and c = 9.0934 (7) Å. By the hydrogen bonds , 4-(Hpd) + cation and (H 2 PO 4 ) - anion were aligned to form an alternatively intercalated three-dimensional framework. Physical properties including thermal performance, linear and nonlinear optical characteristics were identified. On the basis of the results, a high and broad transmittance has been exhibited at the ultraviolet region and the optical band gaps is proved about 3.71 eV for 4-(Hpd)H 2 PO 4 crystal. PL presented an obvious emission peak with the position at 450 nm. SHG response has been demonstrated and the intensity is about 0.15 time that of KDP. In particular, First-principle density functional theory (DFT) calculation was performed to get insight into the correlations between optical properties and electronic structure. The results reveal that the interactions of 4-(Hpd) + cations and (H 2 PO 4 ) - anions are associated with the high transmittance and SHG.