Ba<sub>4</sub>Ga<sub>2</sub>B<sub>8</sub>O<sub>18</sub>Cl<sub>2</sub>·NaCl:  A New Polar Structure with NaCl Inclusion

2006-08-21T00:00:00Z (GMT) by R. K. Li Yi Yu
The title compound, Ba<sub>4</sub>Ga<sub>2</sub>B<sub>8</sub>O<sub>18</sub>Cl<sub>2</sub>·NaCl, is found to crystallize in a polar space group <i>P</i>4<sub>2</sub><i>nm</i> with cell dimensions of <i>a</i> = 12.1134(2) Å and <i>c</i> = 6.8456(1) Å. The basic building blocks of the structure are the B<sub>4</sub>O<sub>9</sub> groups, which are interconnected by the GaO<sub>4</sub> tetrahedron to form a three-dimensional net with Ba<sup>2+</sup> ion-, Cl<sup>-</sup> ion-, and NaCl molecule-filled tunnels. This net structure is closely related to that of mineral hilgardite, with which many variant compounds have been found. Both a powder second-harmonic-generation test and calculations suggest that it possesses an optical nonlinearity comparable to that of potassium dihydrogen phosphate.