A neutron powder diffraction study of fully deuterated laumontite

The crystal structure of fully deuterated laumontite, Ca (sub 4) Al (sub 8) Si (sub 16) O (sub 48) bullet 18D (sub 2) O, has been refined using the Rietveld method (C2/m, Z = 1; a 14.863, b 13.169, c 7.537 Angstrom, beta 110.18 degrees ; 1374 reflections, R (sub F) 0.63%); the specimen was immersed in D (sub 2) O during data collection. Of the four water sites, 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. Local cation and/or water vacancies will disrupt the ordering scheme and result in an average symmetry in agreement with the overall symmetry.