Crystal Structure Determination of Tetrabarium-digalliumoxide, Ba4Ga2O7

Abstract

Single crystals of a new barium oxogallate were obtained by growth from a melt at 1500°C. The compound is monoclinic, with cell parameters a = 17.7447(10) A Ê , b = 10.6719(5) A Ê , c = 7.2828(5) A Ê , b = 98.962(7)°, V = 1362.3(2) A Ê 3 . The diffraction pattern shows systematic absences corresponding to the space group P12 1 /c1. The structure was solved by direct methods followed by Fourier syntheses, and refined using a single crystal diffraction data set (R1 = 0.032 for 2173 reflections with I > 2r(I)). The chemical composition derived from structure solution is Ba 4 Ga 2 O 7 , with a unit cell content of Z = 6. Main building units of the structure are GaO 4 tetrahedra sharing one oxygen atom to form Ga 2 O 7 groups. The Ga±O±Ga bridging angle of one of the two symmetrically independent groups is linear by symmetry. The dimers are crosslinked by barium cations coordinated by six to eight oxygen ligands.

Bond-length distributions for ions bonded to oxygen: metalloids and post-transition metals

“…The minimum reliable distance occurs in BaGa 2 O 4 (Kahlenberg et al, 2000) in which there is one O 2À ion bridging two GaO 4 tetrahedra and not bonded to Ba 2+ . Ga 3+ -O 2À bonds are in the range 1.91-1.94 Å and occur in the structures of Sr 4 (Ga 2 O 7 ) (Kahlenberg et al, 2005) and Ba 4 (Ga 2 O 7 ) (Kahlenberg, 2001). [5] Ga has grand mean bond length of 1.910 Å and a range of 1.771-2.254 Å .…”

Bond-length distributions for ions bonded to oxygen: Metalloids and post-transition metals

“…The minimum reliable distance occurs in BaGa 2 O 4 (Kahlenberg et al, 2000) in which there is one O 2À ion bridging two GaO 4 tetrahedra and not bonded to Ba 2+ . The [4] (Kahlenberg et al, 2005) and Ba 4 (Ga 2 O 7 ) (Kahlenberg, 2001). [5] Ga has grand mean bond length of 1.910 Å and a range of 1.771-2.254 Å .…”

Tetrastrontium-digalliumoxide (Sr4Ga2O7)—synthesis and crystal structure of a mixed anion strontium gallate related to perovskite

“…Ba 4 Ga 2 O 7 , for example, adopts a crystal structure containing [Ga 2 O 7 ]-dimers exclusively [16]. On the other hand, a mixed anion structure very similar to Sr 4 Ga 2 O 7 is realized in Ba 4 Al 2 O 7 [17]: this compound is built up from the same single and triple tetrahedra in the same ratio 1:1.…”