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Recognition and Treatment of Background Problems in Neutron Powder Diffraction Refinements

  • W. H. Baur (a1) and R. X. Fischer (a1)

Abstract

Irregular backgrounds in time-of-flight neutron powder diffraction data and nonlinear backgrounds in angle dependent neutron powder diffraction data. were corrected by fitting fifth degree polynomials to those portions of the data most affected. The anomalous background intensities were in both cases due to non Bragg scattering. The polynomial fitting was carried out over a sufficiently widerange of the profile to avoid interfering with the Bragg peaks. The corrected data gave internally consistent results for the crystallographically nonequivalent (Si,Al) -0 (1) and(Si, Al) -0 (2) bond lengths in zeolite rho and compare favorably with previous refinements of this Zeolite in space group Im3m. Internal and external in consistencies of bond lengths are just as diagnostic of refinement difficulties as negative isotropic temperature factors or non positive definite an isotropic temperature factors are.

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Baerlocher, C. 1984, The X-ray Rtetveld System XRS-84, Acta Cryst., MO. C368.
Baur, W.H., 1970, Bond length variation and distorted coordination polyhedra in inorganic crystals, Trans. Amer, Cryst. Assoc, 6, 129.
Baur, W.H., 1978, Variation of mean Si-O. Fond lengths in silicon-oxygen tet-rahedra, Acta Cryst., B34, 1751.
Baur, W.H., and Ohta, T., 1982, The SisO6 pentamer in zunyite refined and empirical relations for individus) silicon-oxygen bonds, Acta Cryst., B38, 390.
Baur, W.H., Titlmanns, E., and Hofmeister, W., 1983, Topological analysis of crystal structures, Acta Cryst., B39, 669.
Enzo, S., Parrish, W., 1984 A Method of background subtraction for the analysis of broadened profMes, in “Adv. in X-Ray Analysis. Vol. 27”, Cohen, J.B., Russ, J.C., Leyden, D.E., Barrett, O.S., Predecki, P.K., eds., Plenum Press, New York.
Fischer, R.X., Baur, W.H., Shannon, R.D., Staley, R.H., Vega, A.J., Abrams, L., and Prince, E., 1985, Neutron powder diffraction study and phystcal characterization of zeolite D-rho deep-bed calcined at 500°C. nd 65O°C. in preparation.
Fischer, R.X., Baur, W.H., Shannon, R.D., Staley, R.H., Vega, A.J., Abrams, L., Corbin, D.R., and Jorgensen, J.D., 1986b, Neutron powder diffraction study and physical characterization of zeolite D-rho shal-low-bed calcined at 500°C. nd 600°C. in preparation.
Fischer, R.X., Baur, W.H. , Shannon, R.D., Staley, R.H., Vega, A.J., Abrams, L., and Prince, E., 1986c, Neutron powder diffraction study and physical characterization of Zeolite ZK-5 calcined at 500°C. nd 650°C. in preparation.
Immirzi, A., 1980, Constrained powder-profiie refinement based on generaliaed coordinates, Acta Cryst., B36, 2378.
Jorgensen, J.D., and Faber, J., 1983b Electronically focused powder diffractometers at IPNS-I. in “Proc. 6th Meeting International Collab. Advanced Neutron Sources”, Argonne National Laboratory, ANL-82-80.
McCusker, L.B., 1984, Crystal structures of the ammonium and hydrogen forms of zeoli te rho, Zeoli tes, 4. 51.
McCusker, L.B., and Baerlocher, C. 1984, The effect of dehydration upon the crystal structure of zeolite rho, in “Proceedings of the 6th International Conference on Zeolites, Reno, 1983”, Oison, D. and Bisio, A., eds., Butterworth: Guildford.
Pariee, J.B., Gier, T.E., Corbin, D.R., and Cox, D.E., 1984, Structural changes occuring upon dehydration of zeolite rho, J. Phys. Chem. 88, 1635.
Prince, E., 1980. Modification to the Rietveld powder refinement program, National Bureau of Standards, Technical Note 1117, 8.
Prince, E., and Santoro, A., 198O. The five detector neutron powder diffractometer, National Bureau of Standards, Technical Note 1117, 11.
Richardson, J.W., Pluth, J.J., Smith, J.V., and Faber, J., 1985. Fourier-fi1 tering techniques for the analysis of high-resolution pulsed neutron diffraction data, Abstracts of 34th Annual Denver Conference on Applications of X-ray Anatysis, Univ. Denver Research Institute, Denver.
Rietveld, H.M., 1969, A Profile refinement tnethod for nuclear and nagnetic structures, J. Appl. Cryst. 2, 65.
Rotetia, F.J., 1982, “users manual for Rietveld analysis of time-of-f1ight neutron powder data at IPNS”, revised 1984, Intense Pulsed Neutron Source, Argonne National Laboratory.
Shannon, R.D., 1976, Revised effective ionic radii and systematic studies of interatomic distances in halides and chalcogenides, Acta Cryst., AJ2, 751.
Shirley, R., 1984, Measurement and analysis of powder data from single solid phases, in “Hethods and applications in crystallographic Computing”, Hall, S.R. and Ashida, T., eds., Oxford Univ. Press: Oxford.
Von Dreele, R.B., Jorgensen, J.D., and Windsor, C.G., 1982, Rietveld refinement with spallatiori neutron powder diffraction data, J. Appl. Cryst. 15, 581.
Wiles, D.B., and Young, R.A., 1981, New computer program for Rietveld anslysis of x-ray powder diffraction patterns, J. Appl. Cryst., 14, 149.

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