STRUCTURE REFINEMENT OF SYNTHETIC DEUTERATED KAOLINITE BY RIETVELD ANALYSIS USING TIME-OF-FLIGHT NEUTRON POWDER DIFFRACTION DATA

The crystal structure of synthetic deuterated kaolinite was refined by Rietveld analysis using time-of-flight (TOF) neutron powder diffracti on data. For non-hydrogen atoms, CI symmetry was assumed. Starting mod els were tested in which only the direction of O-D vectors was varied. The constraints were introduced to all Al-O, Si-O and O-D bonds. The refinement adopting the former gives Pl(Cl), a = 5.169(1) Angstrom, b = 8.960(2) Angstrom, c = 7.410(2) Angstrom, alpha = 91.26(2)degrees, b eta = 104.99(2)degrees, gamma = 89.93(1)degrees, R-wp = 3.17%, R-I = 5 .78% and S = 1.34 with constraints of l(Al-O) = 1.93 +/- 0.05 Angstrom , I(Si-O) = 1.62 +/- 0.03 Angstrom and l(D-O) = 0.95 +/- 0.15 Angstrom . The inner O-D vector points toward the tetrahedral sheet. All inner- surface O-D groups form H bonding with basal O atoms in the next kaoli nite layers. The results agreed with those obtained from natural kaoli nite.