D.F. Mullica

Structural investigations of YPO4, ScPO4, and LuPO4

Abstract YPO4, ScPO4, and LuPO4 crystallize in the tetragonal system conforming to space group model I41/ amd (D194h, No. 141), Z = 4. The refined crystal structures have been determined from three-dimensional single-crystal X-ray diffraction data. Final least-squares full-matrix refinement yielded respective R-values of 0.024, 0.028, and 0.038. The metal atom in each compound is 8-coordinated to oxygen atoms. The resultant polyhedron is viewed as two interpenetrating tetrahedra forming a bis-bisphenoid (D2d). The phosphate group in each compound is a distorted tetrahedron. Important bond and contact distances and bond angles as well as Ortep-II drawings are presented to foster a wider base for future investigations related to potential employment of lanthanide orthophosphates as hosts for radioactive nuclear waste.

Ninefold coordination LaPO4: Pentagonal interpenetrating tetrahedral polyhedron

Abstract The crystal structure of LaPO4 has been determined from three-dimensional single-crystal X-ray diffraction data. The respective residual indices R1 and R2 have been refined to 0.020 and 0.021, based on 625 unique reflections. Crystallization occurs in the monoclinic space group P21/n (No. 14) with a = 6.825(4), b = 7.057(2), c = 6.482(2) A, and β = 103.21(4)°. Z = 4. The lanthanum metal atom is nine-coordinated to oxygen atoms forming a polyhedron best described as a pentagonal interpenetrating tetrahedron. The nine-coordinated La atoms are linked together by distorted tetrahedral phosphate groups. Important interatomic distances and angles are presented.

The structure of cerium orthophosphate, a synthetic analogue of monazite

The crystal structure of CePO4 has been determined by modern X-ray crystallographic techniques. The unit cell is monoclinic (space group P21n) with a = 6.7777(3), b = 6.993(3), c = 6.445(3) A, and β = 103.54(4)°. The final least-squares refinement yielded R = 0.0276, and Rw = 0.0280. The structure is made up of irregular 9-coordinated cerium atoms linked together by distorted tetrahedral phosphate groups. Comparisons with previous structural determinations of naturl monazites are made. A potential application of the lanthanide orthophosphates as a nuclear waste matrix material is briefly discussed.

Coordination geometry and structural determinations of SmPO4,EuPO4 and GdPO4

Abstract SmPO 4 , EuPO 4 , and GdPO 4 crystallize in the monoclinic system conforming to space group P 2 1 / n (No. 14, Z = 4). The structures and coordination geometries of these three lanthanide orthophosphates have been determined by means of automated three-dimensional single crystal diffractometry using Mo Kα radiation. The lattice parameters of the three compounds are as follows: For SmPO 4 , a = 6.669(1), b = 6.868(2), c = 6.351(1) A, and β = 103.92(2)°; for EuPO 4 , a = 6.639(3), b = 6.823(3), c = 6.318(3) A and β = 104.00(4)°; and for GdPO 4 , a = 6.621(2), b = 6.823(2), c = 6.310(2) A, and β = 104.16(2)°. Final full-matrix least-squares refinements resulted in the following residual indices for SmPO 4 , EuPO 4 , and GdPO 4 , respectively: R = 0.034, 0.033, and 0.031 and R w = 0.034, 0.033, and 0.032. These results were based on 1103, 751, and 1073 reflections, respectively, for the three systems. The lanthanide atoms in this structure are coordinated to nine oxygen atoms forming a polyhedron, which has been described as a pentagonal interpenetrating tetrahedron. Important bond and contact distances and bond angles are presented along with ORTEP-II drawings that illustrate the coordination geometry.

Structural investigations of several LnVO4 compounds

Refinements of the crystallographic structures of SmVO4, EuVO4, GdVO4 and DyVO4 have been carried out by means of three dimensional single-crystal X-ray diffractometry. These orthovanadate compounds crystallize in the tetragonal space group 141/amd (Z = 4) with respective lattice constants of a = 7.2647(9), 7.2358(7), 7.2122(7), 7.1429(8) A and c = 6.384(1), 6.362(1), 6.346(2), 6.300(2) A. Anisotropic refinements of the structural data using a full-matrix least-squares program yielded final reliability (R) factors of 0.026, 0.049, 0.042 and 0.041 based on 266, 273, 261 and 220 unique reflections for Ln = Sm, Eu, Gd and Dy, respectively. The lanthamide (Ln) atoms are eight-coordinated to oxygen atoms with two unique LnO bond lengths. These non-equivalent vertices form two bisphenoidal sets. A distorted triangulated dodecahedron is produced by connecting the oxygen vertices. The orthovanadate group in each compound is a distorted tetrahedron. Important crystal data, parameters, bond lengths and angles are tabulated.

Structural refinements of praseodymium and neodymium orthophosphate

The crystal structures of PrPO4 and NdPO4 have been determined by single crystal X-ray diffraction techniques. The structures are isostructural with CePO4 and LaPO4, and are monoclinic in space group P21n. The cell constants are a = 6.741(3), b = 6.961(4), c = 6.416(3) A, and β = 103.63(3)° for PrPO4 and a = 6.722(1), b = 6.933(1), c = 6.390(2) A, and β = 103.72(2)° for NdPO4. The least-squares structural refinements of PrPO4 and NdPO4 yielded R values of 0.034 and 0.038 based on 810 and 947 unique reflections, respectively. The lanthanide metal atoms are coordinated with nine oxygens and are linked together by very slightly distorted tetrahedral phosphate groups. The nine oxygen atoms ligating the lanthanide atoms form a polyhedron that is best described as a pentagonal interpenetrating tetrahedron.

THE STRUCTURES OF THREE LANTHANIDE ORTHOPHOSPHATES

Abstract TbPO 4 , DyPO 4 , and HoPO 4 crystallize in space group [4 1 /amd (No. 141), zircon structure, Z=4. The crystal structures have been determined from automated three-dimensional single crystal X-ray diffraction analyses. Least-squares full matrix refinements yielded final weighted R-values equal to 00.035, 0.037, and 0.036, respectively. The lanthanide metal atom in each compound is eight-coordinated to oxygen atoms forming two orthogonal interpenetrating tetrahedra. Each tetrahedron has distinct bond distances. The resultant polyhedron is best described as distorted dodecahedron (D 2d ). Important crystal data, parameters, bond lengths, and angles are tabularized.

The X-ray photoemission spectra of Nd(OH)3, Sm(OH)3, Eu(OH)3 and Gd(OH)3

Abstract Experimental XPS spectra of lanthanide trihydroxides (Ln(OH)3, where Ln is Nd, Sm, Eu or Gd) at Ln3+5p, 5s, 4d, 4p, 4s, and 3d and OH− 2σ, 3σ and 1π levels are reported. A process of computation obtained by combining Wendins quasi-particle method and the Johansson-Martenssen method with first-order correction is employed in this work to explain the observed physical phenomena. The derived model implies that the spectral function of a long lifetime quasi-particle is a Gaussian function, locates the atomic orbital energy, corrects the variation in binding energy due to the correlation energy, calculates semi-empirically the dipole relaxation energy shift, and accounts for the atom-to-solid core level shift. Valence band XPS spectra, Ln3+ 4d, 4p, 4s, 3d and experimental and theoretical binding energies of Nd3+, Sm3+, Eu3+ and Gd3+ in Ln(OH)3 are tabulated. It is conspicuous that the 4f and 5d orbital collapses are responsible for the interesting features of three giant Coster-Kronig fluctuations, 5 s 1 ⇌ 5 p 2md1 (m = 5, 6, 7, …), 4 p 1 ⇌ 4 d 2mf1 (m = 4, 5, 6, …) and 4 s 1 ⇌ 4 p 14 d 1mf1 (m = 4, 5, 6, …), and the “satellite complex” in the 3d core hole spectra.

The crystal structure of cubic In(OH)3 by X-ray and neutron diffraction methods☆

Abstract Single crystals of indium trihydroxide were obtained by hydrothermal methods at varied concentrations and temperatures. The cubic form of indium trihydroxide crystallizes in space group Im , 3( T 5 h ), with a lattice constant of 7.9743(6) A. The expermental and calculated densities are 4.38 g cm −3 and 4.344 g cm −3 , respectively. An analysis of indium trihydroxide has been carried out by single crystal X-ray diffraction methods. The final refinement based on 106 independent reflections yields a conventional R value of 1.48%. Six oxygen atoms are octahedrally coordinated about each indium atom, and each oxygen atom is coordinated by two indium atoms. A neutron diffraction investigation verifies the conclusions obtained from the X-ray study and additionally shows the hydrogen atoms to be disordered. The 157 observed independent reflections obtained on a computer-controlled four-circle diffractometer yield a final R value of 3.09%. Indium trideuteroxide has been prepared in order to compare the IR spectra of In(OH) 3 and In(OD) 3 . Two different strengths of hydrogen-bonding are noted for the disordered hydrogens. The study of indium trihydroxide is part of a research program investigation the structure and morphology of M(OH) 3 compounds, which include the lanthanide trihydroxides. Indium trihydroxide is isomorphous with scandium trihydroxide and a newly-found cubic lutetium trihydroxide.

Structure of dichromate-type lead pyrophosphate, Pb2P2O7

Abstract Lead pyrophosphate, Pb2P2O7, crystallizes in the triclinic space group P 1 (Z = 4) with a = 6.914(2), b = 6.966(2), c = 12.751(4) A; α = 96.82(3), β = 91.14(3), γ = 89.64(3)°; and V = 612.0(6) A3. Structural refinement data were collected using an automated diffractometer with MoKα radiation. The lead pyrophosphate structure was refined by a full matrix to an R of 0.069 (Rw = 0.067) using 2637 unique reflections. The structure has two unique diphosphate groups that are repeated by lattice translations to form sheets of diphosphate groups. The P2O7 groups, dichromate type, are eclipsed to within 9.4 and 13.5°. The Pb2+ ions are eight- and nine-coordinated to oxygen atoms with average experimental interatomic distances of 2.695 and 2.767 A, respectively.