The crystal structure of silver tetraborate Ag2O.4B2O3

Crystalline Ag~O.4B203 has been prepared and fotmd to be monoclinic with unit-cell dimensions a=6.550±0-003, b=8-671 ±0.004, c=17.511___0.008A; fl=90 ° 18'±6'.The space group is P21/c.A crystal structure investigation was carried out on a solid solution of this phase, where 40 mol.% of the silver atoms were substituted by sodium atoms.This solid solution had unit-cell dimensions a = 6.521 ± 0.003, b = 8.624 ± 0.004, c = 17.549 ± 0-008 A; fl = 90 ° 20' ± 5'.A total of 829 reflexions were recorded.The structure was determined by a three-dimensional Fourier synthesis, and refined by a least-squares analysis, including all observed reflexions.A reliability index of R = 11.0%was obtained.The borate anion in the structure consists of two separate, identical, three-dimensional, interlocking networks.Each of these networks is composed of units which have previously been found in anhydrous triborates and pentaborates.A structural relationship of silver tetraborate to sodium tetraborate is indicated.