Active performance of tetrahedral groups to SHG response: theoretical interpretations of Ge/Si-containing borate crystalsElectronic supplementary information (ESI) available: Different R-O patterns of KBGeO6 and Li4B4Si8O24; band structures of KBGe2O6, Li4B4Si8O24, LaBSiO5, LaBGeO5, Rb4Ge3B6O17, RbGeB3O7 and Rb2GeB4O9; density of state (DOS) of KBGe2O6, Li4B4Si8O24, LaBSiO5, LaBGeO5, Rb4Ge3B6O17, RbGeB3O7 and Rb2GeB4O9. See DOI: 10.1039/c5cp07313h

• Main Authors: Li, Linping, Yang, Zhihua, Lei, Bing-Hua, Kong, Qingrong, Lee, Ming-Hsein, Zhang, Bingbing, Pan, Shilie, Zhang, Jun
• Format: Journal Article
• Published: 17.02.2016
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c5cp07313h

As potential candidates for deep-UV nonlinear optical (NLO) crystals, borosilicates and borogermanates, which contain NLO-active groups such as B-O, Si-O and Ge-O, have fascinated many scientists. The crystal structures, electronic structures and optical properties of seven borates in different B/R (R = Si, Ge) ratios have been studied using DFT methods. Through the SHG-density, we find that besides the recognized contribution of the π-conjugation configuration of BO 3 to second harmonic generation (SHG), the tetrahedra have a non-negligible influence. This is because the non-bonding p orbitals of the bridging oxygen in the tetrahedra are observably closer to the Fermi level than those in BO 3 , which is observed in the PDOS of Rb 4 Ge 3 B 6 O 17 and RbGeB 3 O 7 . This conclusion would be very meaningful in the understanding of the relationship between the crystal structure and nonlinear optical properties. Besides the recognized contribution of the π-conjugation configuration of BO 3 to SHG responses, the bridging oxygens between the tetrahedra have a non-negligible influence.