The crystal structure of delta-Na2Si2O5

The crystal structure of delta-Na2Si2O5 has been solved and refined to an R index of 0.053 for 933 independent reflections. The compound is monoclinic with space group P2(1)/n (a = 8.393(2) Angstrom, b = 12.083(3) Angstrom, c = 4.843(1) Angstrom, beta = 90.37(3)degrees, V = 491.1(1) Angstrom(3), M-r = 182.15 u, Z = 4, lambda(MoK alpha)= 0.71073 Angstrom, D-x = 2.46 g/cm(3) , mu(MoK alpha) = 8.3 cm(-1)). The crystal showed twinning by pseudo-merohe dry according to 2(100), a feature which we took account of in the refineme nts. The compound belongs to the group of single layer silicates. Individua l sheets can be described as being built by the condensation of zweier sing le chains of SiO4 tetrahedra parallel to the c-axis or, alternatively, by c ondensation of vierer single chains parallel to the a-axis. The stacking of the layers parallel to the b-axis results in a three-dimensional structure in which the sodium cations reside between the layers for charge compensat ion. (C) 1999 Academic Press.