A neutron powder diffraction study of fully deuterated laumontite
Ståhl, Kenny; Artioli, Gilberto
European Journal of Mineralogy Volume 5 Number 5 (1993), p. 851 - 856
published: Jan 1, 1992
manuscript accepted: May 19, 1993
manuscript received: Dec 22, 1992
ArtNo. ESP147050505014, Price: 29.00 €
Abstract The crystal structure of fully deuterated laumontite, Ca4Al8Si16048-18D20, has been refined from neutron powder diffraction data using the Rietveld method, λ = 1.468(1) Å, T = 295 K, Cllm, Z = 1, Mr = 1935.94, a = 14.863(2), b = 13.169(2), c = 7.537(1) Å, ß = 110.18(1)°, V= 1384.7(6) Å3, 6.04° < 26 < 125.00° in 1488 steps, Rp = 3.57 %, Rwp = 4.57 %, G0F = 1.61, RF = 0.63 % (1374 Bragg reflections) and 96 refined parameters. The sample was submerged in D2O during data collection. A D2O spectrum was measured separately and, after smoothing, subtracted from the laumontite spectrum. Of the four water sites present, two are coordinated to Ca while the other two act as bridges between the Ca-coordinated waters through hydrogen bonding. All water sites are disordered to some degree and essentially fully occupied. Elementary restrictions on bond distances and angles to the apparently large number of possible water arrangements impose a high degree of local water ordering. Local cation and/or water vacancies will disrupt the ordering scheme and result in an average symmetry in agreement with the overall symmetry.