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Dive into the research topics where W.O. Milligan is active.

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Featured researches published by W.O. Milligan.


Inorganica Chimica Acta | 1982

Structural investigations of YPO4, ScPO4, and LuPO4

W.O. Milligan; D.F. Mullica; G. W. Beall; L. A. Boatner

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.


Inorganica Chimica Acta | 1984

Ninefold coordination LaPO4: Pentagonal interpenetrating tetrahedral polyhedron

D.F. Mullica; W.O. Milligan; David A. Grossie; G. W. Beall; L. A. Boatner

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.


Journal of Inorganic and Nuclear Chemistry | 1981

The structure of cerium orthophosphate, a synthetic analogue of monazite

G. W. Beall; L. A. Boatner; D.F. Mullica; W.O. Milligan

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.


Journal of Inorganic and Nuclear Chemistry | 1977

Structural trends in the lanthanide trihydroxides

G.W. Beall; W.O. Milligan; Herbert A. Wolcott

Abstract The hydrous lanthanide oxides and hydroxides comprise a complex series of both amorphous and crystalline compounds. One important member of this system is the hexagonal form of M(OH)3 where M studied here are La, Nd, Sm, Gd, Tb, Dy, Ho, Y and Er. The lattice constants and structure for these nine isotypic compounds has been determined by three-dimensional X-ray diffraction. The space group is P63/m or P63 with two formula units per cell. The metal is 9-coordinate (tri-capped trigonal prism) with two independent metal-oxygen bond distances and three independent oxygenz.sbnd;oxygen bond distances. The metaloxygenoxygen bond distances both exhibit monotonic decreases proceeding from La to Er. The metal to oxygen distances range from 2.588(3) A to 2.403(3) A for MO2 and from 2.551(3) A to 2.439(3) A for MO1. At the low atomic number end of the series the MO1, bond distance is shorter than the MO2 bond distance. The two bond distances become the same at the spherically symmetric gadolinium and switch in relative magnitude as you proceed to erbium. The oxygenoxygen bond distances range from 3.033(5) A to 2.856(5) A for O1O2, 2.992(6) A to 2.826(7) A for O2O2 and 2.900(6) A to 2.710(6) A for the second O1O2 bond distance. Approximate positions for the hydrogen atoms have been found for the M(OH)3 compounds Gd, Dy, Ho, Y and Er. A set of crystal radii for the lanthanides La, Nd, Sm, Gd, Tb, Dy, Ho and Er has been derived.


Inorganica Chimica Acta | 1983

THE STRUCTURES OF THREE LANTHANIDE ORTHOPHOSPHATES

W.O. Milligan; D.F. Mullica; G. W. Beall; L. A. Boatner

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.


Journal of Inorganic and Nuclear Chemistry | 1979

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

D.F. Mullica; Gary W. Beall; W.O. Milligan; J.D. Korp; I. Bernal

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.


Journal of Inorganic and Nuclear Chemistry | 1979

Crystal structures of Pr(OH)3, Eu(OH)3 and Tm(OH)3☆

D.F. Mullica; W.O. Milligan; G.W. Beall

Abstract The crystal structures of Pr(OH)3, Eu(OH)3 and Tm(OH)3 have been determined from single-crystal, X-ray diffraction data. The hexagonal form of these lanthanide trihydroxides crystallizes in the space group P63/m(C6h2) with two formula units per unit cell. The respective lattice constants for the trihydroxides of Pr, Er and Tm are a 0 = 6.456(1), 6.352(1), and 6.221(1) A and c 0 = 3.769(1), 3.653(1), and 3.503(2) A . The metal atom of each is 9-coordinate with two unique MO bond distances and three independent OO bond distances. These isotypic compounds have been refined to conventional residual index values of 0.0320, 0.0280 and 0.0199, respectively. Fluorescence and IR data were collected on each of the isomorphous compounds. Refined parameters from this investigation have been added to earlier studies on structural trends in the lanthanide trihydroxides.


Journal of Inorganic and Nuclear Chemistry | 1980

Structural refinement of cubic Lu(OH)3

D.F. Mullica; W.O. Milligan

Abstract The cubic form of lutetium trihydroxide crystallizes in space group Im3(Th5. No. 204) with a0 = 8.2240(3)Ă. Single crystal X-ray diffraction data have been collected on an Enraf-Nonius CAD-4 automated diffractometer, complete to 2θ = 60°. The final full-matrix least-squares refinement based on 69 unique reflections yields an R value of 0.029. The cell contains eight formula units. Each lutetium atom is octahedrally coordinated with six oxygen atoms, and each oxygen is coordinated by two lutetium atoms to form infinite LuOLu chains. Atomic coordinates, temperature factors and other supporting crystallographic and supplementary data are reported. Dehydration, fluorescence, and spectroscopic analyses have been done on single crystals of cubic Lu(OH)3. The observed density is 5.36(4) Mg m−3 (ϱc = 5.396 Mg m−3). The important bond lengths are: LuO = 2.243 A; OO (intermolecular) = 2.728 and 2.972A. Lutetium trideuteroxide has been prepared in order to compare the IR spectra of Lu(OH)3 and Lu(OD)3 with regard to hydrogen bonding.


Journal of Inorganic and Nuclear Chemistry | 1979

Structural refinement of LaCo(CN)6·5H2O☆

D.F. Mullica; W.O. Milligan; W.T. Kouba

Abstract Lanthanum hexacyanocobaltate pentahydrate, LaCo(CN)6·5H2O, crystallizes in a hexagonal unit cell, space group P63/m (C6h2, No. 176), with a 0 = 7.507(2) A and c 0 = 14.343(4) A . Single crystal X-ray diffraction data have been collected on an Enraf Nonius Cad-4 automated diffractometer, complete to 2θ = 70°. The final least-squares refinement based on 533 independent reflections yields a residual index value of 0.039. The calculated density for two molecules in the unit cell is 2.106 g-cm−3 [ϱobs = 2.094(7) g-cm−3]. The trivalent lanthanum metal atoms are linked to the cobalt atoms by cyanide bridging. Three of the five water molecules are strongly coordinated and two are uncoordinated occupying holes in the structure along the threefold axis. Dehydration, fluorescence, and spectroscopic analyses gave also been done on single crystals of LaCo(CN)6·5H2O. The important bond lengths are: LaN = 2.616 A; CoC = 1.887 A; La-0(2) = 2.602 A; and CN = 1.156 A.


Inorganica Chimica Acta | 1982

The structural analysis of NdKFe(CN)6·4H2O

W.O. Milligan; D.F. Mullica; H.O. Perkins

The title compound crystallizes in the hexagonal space group P63/m(C26h, No. 176), with t = 7.358(1) A and c = 13.780(2) A. The experimental density for two molecules in the unit cell is 2.399(5) Mg m−3 (calculated, 2.402 Mg m−3). The single-crystal X-ray diffraction data refined by a full-matrix least-squares method have yielded R1 = 0.0160 and R2 = 0.0165, based on 858 unique reflections. The octahedral FeC6 groups are linked to the nine-coordinated NdN6(H2O)3 groups via cyanide bridging. The uncoordinated water molecule and the potassium ion occupy holes in the structure along a threefold axis above and below the Nd ion. Important bond lengths are: NdN = 2.518(3); FeC = 1.903(3); NdO = 2.685(3); and C = 1.166(4) A.

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G. W. Beall

Oak Ridge National Laboratory

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L. A. Boatner

Oak Ridge National Laboratory

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