Phases of general formula (RE, A)2M3O7 (RE=lanthanide, A=Ca, Sr, Ba; M=Ga, Al) are of interest for their nonlinear optical properties and have potential as solid state lasers. Their structures have been refined using X-ray and neutron diffraction data and are related to gehlenite, Ca2Al2SiO7, with M cations occupying Al and Si sites and RE and A cations sharing the Ca site with no evidence for ordering, although they occur in the ratio 1:1 because of stoichiometry; the M cations are tetrahedrally coordinated. (RE, Ba)2M3O7 compounds cannot be synthesized for M=Al or for RE cations smaller than Sm; this limitation is believed to be due to size mismatch between cations within the structure.

The subsolidus phase relations in the ternary system La2O3–Bi2O3–CuO at 900 °C were investigated by X-ray powder diffraction. A new binary compound, Bi2La4O9, was found, as well as a binary and a ternary solid solution series, Bi1−xLaxO1.5 (0.16≤x≤0.33) and La2−xBixCuO4 (0≤x≤0.11), respectively.

Bafertisite, Ba(Fe, Mn)2Ti(Si2O7)O(OH, Cl)2, has been reported as belonging to three space groups, i.e., Pmmn, P21/m, and Cm. The samples of bafertisite from the original locality Bayan Obo, Inner Mongolia, and from Jiangsu Province, China, were reinvestigated by X-ray methods. On the basis of single-crystal photographs, Pmmn could be ruled out and the relationship between a subcell in P21/m and the true cell in Cm deduced. The transformation matrix from the subcell to the true cell is 002/02¯0/101¯. Using the X-ray powder data, the refined true unit cell parameters in space group Cm are: a=10.612(3), b=13.637(7), c=12.464(2) Å, β=119.49(2)° for Bayan Obo sample, and a=10.633(6), b=13.67(1), c=12.465(5) Å, β=119.55(4)° for the Jiangsu sample. The 00l-reflections, which are rather prominent due to preferred orientation, can only be explained by our new unit cell.

The present paper establishes that the ratio between the XRD pulse counts of cement clinkers at d=0.278 and 0.274 nm bears a distinct relationship with the degree of sintering of the clinker, which is one of the factors that determine the cement quality. The paper also presents a rapid and accurate method for predicting both 3- and 28-day compressive strength (CCS) of cement mortar cubes based on XRD of the cement clinkers. The method is based on an index Xn derived from the XRD pulse counts at d=0.2959 and 0.287 nm corresponding to alite (hkl=202) and belite (hkl=102) phases of the clinker, respectively. The regression equation derived for a particular plant is (1) 3 day CCS=Xn×240 kg/cm2, when Xn<1 and 240+26 (Xn−1) kg/cm2, when Xn>1, where Xnmaximum=5.5. (2) 28 day CCS=C+C×In/100, where C=3 days CCS estimated by XRD (1), In=90−10Xn, where Xnmax=5.5. Calculated CCS values, in average, vary from the conventional test values by +5.9% to −5.4% and +3.8% to −3.5% in cases of 3- and 28-day CCS, respectively.

The phase decomposition occurring during the heating of rapidly quenched Al–Ge–Si alloys has been investigated in situ by means of synchrotron radiation X-ray diffraction. The metastable Al–Ge phases formed in the as-quenched state transform during heating to Al and Ge. The addition of silicon decreases the transformation temperature. A Ge(Si) solid solution is indicated by a systematic change in the lattice constant of Ge as a result of the diffusion of Si from the Al matrix into the phase-separated Ge matrix.

A mathematical model for interpreting the anisotropical broadening of the powder diffraction lines by an average crystallite in the form of a triaxial ellipsoid is developed. The model covers satisfactorily a broad range of averaged crystallite shapes in polycrystalline samples of all crystal symmetries and provides simple formulas for use in powder pattern fitting routines. When ra, rb, rc are the principal ellipsoid radii, and ca, cb, cc direction cosines of diffraction vector related to the principal axes of ellipsoid, the average dimension of crystallites along the diffraction vector (Dhkl) is: Dhkl=K/ca2/ra2+cb2/rb2+cc2/rc2. The coefficient K has the value 3/2 if Dhkl is the volume average dimension of crystallites along the diffraction vector, or 4/3 in the case of the surface average dimension. The appropriate expression for use in whole pattern fitting routines is: b11h2+b22k2+b33l2+2b12hk+2b13hl+2b23kl=K2/Lhkl2dhkl2, where bij are the elements of a second-rank symmetric tensor. Finding eigenvalues and vectors of tensor b gives dimensions and orientations of the principal ellipsoid radii in reciprocal lattice values.

The crystal structure of four cyanometallates has been determined from X-ray powder diffraction data using the Rietveld method. The variously hydrated compounds Cu3[Co(CN)6]2, Mn3[Co(CN)6]2 and KNi[Fe(CN)6] crystallize at cubic symmetry (Fm3m) with lattice parameters 10.032(2), 10.413(3) and 10.234(5) Å, respectively. The crystal of KMn[Fe(CN)6]·2H2O shows a monoclinic structure (P21/c) with the lattice parameters a=10.108(2) Å, b=10.104(3) Å, c=10.114(3) Å, β=92°, 93°. The starting model was based on an isomorphic Mn3[Co(CN)6]2 single crystal structure, where Co and Mn ions are octahedrally coordinated by C and N atoms, respectively, forming three-dimensional bimetallic networks with the C≡N groups as bridging ligands.

The X-ray powder diffraction data of polycrystalline fibrillar zinc trimolybdates ZnMo3O10·3.75H2O, ZnMo3O10·5H2O, and ZnMo3O10·10H2O, are reported. An uncommon diffraction pattern was recorded in the case of the “wet fibers” of ZnMo3O10·10H2O, which could be indexed assuming a model of parallel fibers with translation disorder along the fiber axis. The powder diffraction patterns, lattice parameters, space groups, and other data describing these compounds are presented in this paper.© 1999 International Centre for Diffraction Data.

The subject of the paper is the old and well-known linear least squares method for determining the lattice dimension of a crystalline phase from the peak locations of a powder diffraction pattern. Approximations, limits, and extensions of the method are discussed with reference to the assignment of hkl indices to an experimental multiphase pattern.

Experimental X-ray powder diffraction patterns and refined unit cell parameters for two barium hollandite-type compounds, BaxFe2xTi8−2xO16, with x=1.143 and 1.333, are reported here. Compared to the tetragonal parent structure, both compounds exhibit monoclinic distortions that increase with Ba content [Ba1.333Fe2.666Ti5.334O16: a=10.2328(8), b=2.9777(4), c=9.899(1) Å, β=91.04(1)°, V=301.58(5) Å3, Z=1, ρcalc=4.64 g/cc; Ba1.143Fe2.286Ti5.714O16: a=10.1066(6), b=2.9690(3), c=10.064(2) Å, β=90.077(6)°, V=301.98(4) Å3, Z=1, ρcalc=4.48 g/cc]. The X-ray powder patterns for both phases contain a number of broad, weak superlattice peaks attributed to ordering of the Ba2+ ions within the tunnels of the hollandite framework structure. According to the criteria developed by Cheary and Squadrito [Acta Crystallogr. B 45, 205 (1989)], the observed positions of the (0k1)/(1k0) superlattice peaks are consistent with the nominal x-values of both compounds, and the k values calculated from the corresponding d-spacings suggest that the Ba ordering within the tunnels is commensurate for x=1.333 and incommensurate for x=1.143. High-temperature X-ray diffraction data indicate that the x=1.333 compound undergoes a monoclinic→tetragonal phase transition between 310 and 360 °C.

The X-ray powder diffraction patterns of anilinium trimolybdate tetrahydrate, (C6H5NH3)2Mo3O10·4H2O, and anilinium trimolybdate dihyhydrate, (C6H5NH3)2Mo3O10·2H2O, have been measured in room temperature. The unit cell parameters were refined to a=11.0670(7) Å, b=7.6116(8) Å, c=25.554(3) Å, space group Pnma(62) and a=17.560(2) Å, b=7.5621(6) Å, c=16.284(2) Å, β=108.54(1)°, space group P21(4) or P21/m(11) for orthorhombic anilinium trimolybdate tetrahydrate and monoclinic anilinium trimolybdate dihydrate, respectively.

Crystal data and results of structure refinement, using powder X-ray diffraction and Rietveld analysis, for ε-ordered structures near 75 at. % Ga are reported. The structures are based on the AlB2-type with deviation from stoichiometry due to pairwise substitution of rare earth (RE) atoms by gallium. Weak reflections which are forbidden in the AlB2-type structure were observed and indicate the existence of positional ordering of Ga2 pairs located in the basal planes preserving the hexagonal symmetry (S.G. P6/mmm). This ordering results in a new unit cell with parameters a′, c′, in which a′=a√3 and c′=c. The experimental data of the cells parameters are: a=7.467(2)Å, c=4.276(3)Å for Nd1−xGa2−x (x=0.18), and a=7.400(3)Å, c=4.184(2)Å for Gd1−xGa2+2x (x=0.165).

The structure type of La2Ti10.27Ga9.63O38 was revealed by a search-match using the PDF. A successful Rietveld refinement (Rp=8.9, Rwp=13.3, RB=4.20) confirmed the structure to be rhombohedral (space group R3¯, No. 148) with the refined unit cell parameters a=9.1878(1) Å, α=68.458(1)°, and V=646.374(1) Å3. The structure is compared to other compounds of the davidite type, and the observed and calculated powder data are given.

The two ternary phases W5As2.5P1.5 and Ni4Nb5P4 have been investigated by X-ray powder diffraction. Precise data for the two compounds were collected using CuKα1 radiation over the range 11°–140° 2θ. Unit cell refinements (space group I4/m) led to a=9.4729(3) Å, c=3.2414(2) Å (Dx=13.16 gcm−3) with M20=127, F30=91(0.0092,36) for W5As2.5P1.5 and a=9.9304(4) Å, c=3.5243(3) Å (Dx=7.87 gcm−3) with M20=179, F30=138(0.0068,32) for Ni4Nb5P4.

Indexed X-ray powder diffraction data are reported for the homologous compound (ZnO)5(In1−xYx)2O3. The structures of (ZnO)5In2O3 and of (ZnO)5(In1−xYx)2O3 were refined by the Rietveld technique on the basis of the space group R3¯m. Refined unit cell dimensions are a=3.3285(1) Å, c=58.127(2) Å, V=557.71(3) Å3, Dx=6.11 g/cm3, Rwp=10.52, RB=8.56 for (ZnO)5In2O3, and a=3.3505(1) Å, c=57.863(1) Å, V=562.53(2) Å3, Dx=5.97 g/cm3, Rwp=9.05, RB=6.94 for (ZnO)5(In0.8Y0.2)2O3. The structure of (ZnO)5In2O3 was shown to be isostructural with (ZnO)5LuFeO3. Y3+ ions were determined to be arranged at the 3a-metal sites substituting for In3+ ions.

The crystal structure of γ-Mo4O11 was obtained at room temperature (296 K) by Rietveld analysis with X-ray powder diffraction data. The crystal belongs to orthorhombic system, space group: Pna21, Z=4, Mr=559.753 (Atomic weights 1977), Dx=4.1228 g/cm3, F(000)=1024.0, μ=451.293 cm−1 (Int. Tab. Vol. C, Table 4.2.4.2, p. 193, λ=1.540 60 Å), a=24.4756(5) Å, b=6.7516(1) Å, c=5.4572(1) Å, and V=901.80(3) Å3. The structure was refined to Rwp=5.60%, Rp=4.27%, Rb=3.36%, and Rf=2.74% for 65 parameters with 3541 step intensities and 3055 peaks. Goodness of the fit S=3.35.

The structure and powder diffraction data of Hägg-carbide (χ-Fe5C2) have been redetermined and improved by X-ray diffraction. Experimental values of 2θ, corrected for systematic errors, relative peak intensities, lattice spacings, and the Miller indices of 27 observed reflections up to 100° 2θ are reported. The unit cell is monoclinic (space group C2/c, Z=4) with a=11.588 Å, b=4.579 Å, c=5.059 Å, and β=97.75°. The crystal structure has been refined by Rietveld analysis, resulting in Rwp=0.073.

The crystal structure of disilver(1+) pentacyanonitrosylferrate(2−) was studied by X-ray powder diffraction. IR and Mössbauer spectroscopies, thermogravimetric analysis and density measurements were also carried out. This compound is monoclinic, and its lattice parameters are: a=10.986(3) Å, b=6.4080(10) Å, c=7.4545(19) Å, α=δ=90°, β=102.54°(2).

The crystal structure of 1-amino-4-methoxycarbonyl-3-methyl-8-oxopyrazolo[1,5-a]pyrimidine monohydrate, C9H10N4O3·H2O, from the family of pyrazolo[1,5-a]pyrimidines which demonstrate an activity against the influenzavirus A and coxsackievirus B3, has been determined from laboratory (Guinier-Johannson photograph) powder diffraction data using a grid search procedure. Parameters of the monoclinic cell (P21/a, No. 14, Z=4) at 295 K are a=11.599(7) Å, b=11.550(7) Å, c=8.575(5) Å, β=110.76(4)°. Rietveld refinement (full-pattern-decomposition) gave χ2=4.8(4.5), Rp=0.048(0.043), Rwp=0.065(0.062). The observed microstrain-induced anisotropy of diffraction line broadening was approximated by a quartic form in h,k,l. The obtained results allowed to distinguish between several isomers which were indistinguishable by others methods.

Powder diffraction data for 2-aminophenalenone at 295 K (P21/n, Z=4) are given, strong lines: 7.54/X, 7.26/9, 3.34/3. The cell parameters found are a=3.7213(3), b=16.550(2), c=15.095(2) Å, β=92.61(2)°. The crystal structure was determined using powder data and refined giving Rb=0.089. Disordered molecules form stacks along [100] with interplanar spacing of 3.48 Å.