The Monte Carlo method is applied to finding missing atoms in solving inorganic crystal structures without applying a rigid-body approximation. Whole powder patterns of α-SiO2 and Mg2SiO4 were used for testing a procedure. Four atoms among the six in the asymmetric unit of Mg2SiO4 could be found in the present analysis. The use of well-refined profile parameters enhanced the frequency of correct structure configurations in the Monte Carlo search. Utilizing structural information available for constructing a trial configuration is also considered to be important for efficiently searching the structure solution. A procedure for assignment of equivalent positions to respective atoms is presented. The method can be used as a powerful tool for finding missing atoms in a partially solved structure. A histogram of weighted reliability index in Monte Carlo calculations is very informative for evaluating the performance of the method. ©

Modern powder diffraction employing computer-controlled diffractometers now allows quantitative analytical methods to use the whole diffraction trace rather than only individual peaks. Two such methods are in common use: the Rietveld method, which refines the crystal structures of the component phases as part of the matching calculation, and the pattern-fitting method, which uses reference patterns from a database. Potential accuracies of these methods seems to be around 1% absolute. The most severe limitation on the potential accuracy of these methods is particle statistics, which has been reviewed in considerable detail.

The crystal structures of two manganese hexacyanometallates(II), Mn2[Fe(CN)6].8H2O and Mn2[Os(CN)6].8H2O, were refined from X-ray powder diffraction data using the Rietveld method, with the reported structure for Mn2[Ru(CN)6].8H2O used as a structural model. These compounds are isomorphous and crystallize in the monoclinic space group P21/n. Their crystallization water is not firmly bound and can be removed without disrupting the M–C≡N–Mn network. In the dehydrated complexes, the outer cation (Mn) remains linked to only three N atoms from CN ligands while the inner cation (Fe,Os) preserves its coordination sphere. The IR, Raman, and Mössbauer spectra for the hydrated and anhydrous forms are explained based on the refined structures.

New X-ray powder diffraction patterns for two cholesterol derivatives, cholest-4-ene-3,6-dione and cholest-4-en-3-one are reported in the range 0<2θ<115°. Both compounds crystallize in similar monoclinic cells in space-group P21, with unit cell parameters a=10.481(3) Å, b=8.0354(8) Å, c=14.677(3) Å, β=105.265(7)°, V=1192.5(4) Å3 for C27H42O2, and a=10.703(2) Å, b=7.8750(6) Å, c=14.660(3) Å, β=105.205(14)°, V=1192.4(4) Å3 for C27H44O. The patterns, confirmed by single-crystal studies, do not match the PDF 17-1144 and PDF 10-649. A fitting of the overall parameters was performed with Fullprof using the atomic parameters obtained from single-crystal studies.

Our X-ray powder diffraction data determine that UTeO4 has an orthorhombic unit cell with parameters: a=10.115±0.003 Å, b=10.706±0.002 Å, c=7.833±0.002 Å, and v=848±0.40 (Å)3, i.e., the cell volume twice as large as that of UTeO5. IR spectral studies show that UTeO4 and UTeO5 have almost an identical molecular symmetry. In UTeO4, the effective environment of U and Te remains nearly the same as in UTeO5 and the UO2 group is noncentrosymmetric and nonlinear with little or no interaction with equatorial oxygen. Frequencies of the characteristic stretching bands of UTeO4 are (cm−1): νas (O=U=O)=945, νs (O=U=O)=880, νs (Te–O)eq=818, νas (Te–O)eq=749, νas (Te–O)ax=649, νs (Te–O)ax=561.

LiCu2O2 crystals grown by spontaneous crystallization from the fluxed melt were studied by powder X-ray diffraction. The phase analysis shows that the applied growth conditions are suitable for preparation of a single-phase compound. The as-grown crystals contain only traces of foreign phases (Li2CuO2, CuO, Cu2O) typical for preparation of the LiCu2O2 compound. Attempts to anneal or quench the as-grown crystals led to two-phase samples containing LiCu2O2 and LiCu3O3. X-ray powder diffraction pattern of a LiCu2O2 crystal is reported and compared with literature data. The crystal structure is orthorhombic, space group Pnma, in agreement with literature data. Lattice parameters of the studied sample are a=5.7286(2) Å, b=2.8588(1) Å, and c=12.4143(3) Å. Time evolution of a diffraction pattern illustrates a slow increase of the secondary-phases contribution assumed to be due to interaction of the powdered crystal with humid air. A brief summary of compounds known in the Li–Cu–O system is included

A new copper phosphate, CuPO4H⋅0.5H2O, was synthesized using a low temperature hydrothermal method and characterized by powder X-ray diffraction, thermogravimetric analysis, and chemical analysis. The material is monoclinic, space group P21/c, with a=10.6524(2), b=8.4730(2), c=9.2204(2), β=92.43(0), and V=831.47 Å3.

Ca3−xSrxCo4O9 with different compositions (x=0, 0.15, 0.3, and 0.45) were synthesized from stoichiometric mixtures of Co3O4, CaCO3, and SrCO3, and their unit-cell parameters were determined. The powders were mixed with silicon standard powder, and XRD patterns were collected and analyzed using TOPAS. The compounds were determined to be monoclinic with space group of P2. Unit-cell parameters changed from a=4.8329(3) Å, b=4.5727(1) Å, c=10.8360(4) Å, and β=98.093(7)° when x=0, to a=4.8432(1) Å, b=4.6100(3) Å, c=10.8668(3) Å, and β=98.110(5)° when x=0.3. An unidentified second phase was observed when x=0.45.

Powder diffraction data and refined unit cell parameters of two palladium borides were determined. For Pd3B (space group Pnma; Fe3C type) it was found that a=0.54602(3) nm, b=0.75596(4) nm, c=0.48417(4) nm and for Pd5B2 (space group C2/c; Mn5C2 type) a=1.27759(12) nm, b=0.49497(5) nm, c=0.54704(4) nm, β=97.049(7)°. Further, it was shown that the position of the principal scattering peak of the amorphous Pd2B fulfils the Nagel–Tauc criterion about glass forming ability.

X-ray powder diffraction data, unit-cell parameters and space group for a new chiral Kemp’s acid diamide, C18H28N2O3, are reported [a = 12.456(2) Å, b = 12.471(2) Å, c = 12.088(2) Å, β = 99.003(2)°, unit-cell volume V = 1854,48 Å3, Z = 4, space group P21]. All measured lines were indexed and are consistent with the P21 space group. No detectable impurity was observed.

Calcium hydroxyapatite (Ca10(PO4)6(OH)2) whiskers were prepared by using the technique of molten salt synthesis with the fluxing agent of potassium sulphate (K2SO4). A tentative x-ray diffraction (XRD) pattern was suggested for the produced whiskers. Phase purity, composition, and morphology of the whiskers were investigated by powder XRD, inductively coupled plasma-atomic emission spectroscopy, Fourier transform infrared spectroscopy, and scanning electron microscopy, respectively.

X-ray powder diffraction data are reported for a series of multipyrazole compounds in this paper. This work shows that the unit cell dimensions determined by single crystal agree well with those of powder diffraction analysis.