Joseph J. Pluth

Structural features of aluminophosphate materials with

Abstract The aluminophosphates with Al P = 1 form a sub-group of the wide range of phosphates important in biochemistry, soil chemistry, geology and industrial chemistry. The Al and P positions of each 1:1 aluminophosphate structure can be related to alternating nodes of a four-connected 3D net. Descriptions are given of: berlinite (net 90); AlPO4-cristobalite (net 1); AlPO4-tridymite (net 2); AlPO4-20 (sodalite, net 108); variscite (net 5); metavariscite (net 3); AlPO4-5 (net 81); AlPO4-1.5H2O (net 24a); AlPO4-21 and -25 (net 401); AlPO4-15 (net 400); AlPO4-14 (analogous to GaPO4-14, net 399); AlPO4-EN3 (net 402); AlPO4-12 (related to net 398 by changing a linkage). The crystal chemistry of the 1:1 aluminophosphates is different from that of the zeolites because of electrostatic neutrality of the AlPO4 moiety, occurrence of some Al atoms in five or six coordination with oxygen species including OH and H2O, and strict alternation of Al and P atoms on tetrahedral nodes around even-numbered circuits. The aluminophosphate structure types range from dense phases through the hydrates and semi-dense phases to the newly-synthesized microporous materials, which become molecular sieves upon removal of encapsulated material. There is no simple answer to the extent that encapsulated material acts as a template during synthesis. Polytypic variations have not been reported. Integrowths related by simple structural changes are theoretically possible. Observed and calculated X-ray powder patterns are given for seven phases.

Aluminophosphate molecular sieve AlPO4-11: partial refinement from powder data using a pulsed neutron source

Abstract The crystal structure of AlPO 4 -11 is an open aluminophosphate framework containing a 10-ring channel obtained by removing two opposing columns of opposing four-rings from the alternating columns of four- and six-rings that surround the 12-ring channel in AlPO 4 -5.

The framework topology of magnesiumaluminophosphate structure type 36

Abstract The crystal structure of MAPO-36 was solved and refined by combining information obtained bysynchrotron powder, Weissenberg single crystal (of an imperfect crystal), and electron and GuinierLenne powder diffraction. The powder pattern was indexed using a monoclinic cell (C2/c) with a = 13.148, b = 21.577, and c = 5.164 A and β = 91.84°. Powder patterns were calculated for hypothetical models having similar cell parameters and a match was finally achieved for a model related to but topologically different from cancrinite. The aluminophosphate-based molecular sieve structure type 36 is based on the 4.6.12 two-dimensional net (gml) and the double zigzag chain (zz), but unlike cancrinite, it has both radial and tangential chains around the 12-ring. This gives an elliptical channel with staggered annular side pockets. Even though it has smaller channels, these side pockets give it a greater adsorption capacity than that of AIPO-5.

The structures of as-synthesized AlPO4-53(A), calcined dehydrated AlPO4-53(B), and AlPO4-53(C), a new phase determined by the FOCUS method

Abstract AlPO 4 -53 was synthesized hydrothermally with methylamine as a structure-directing agent. The structure of as-synthesized AlPO-53(A) was solved using AlPO-EN3 as a starting model. The Rietveld refinement converged ( R P = 0.140) in space group P2 1 2 1 2 1 ( a =10.3212(1) A, b =13.6308(1) A and c =17.4539(1) A) for unit cell composition: Al 24 P 24 O 96 ·8.5CH 3 NH 2 ·14H 2 O. AlPO-53(A) is isotypic with as-synthesized AlPO-EN3, JDF-2, UiO-12-as, and presumably CFSAPO-1(A). The structure of calcined dehydrated AlPO-53(B) was solved by direct methods, and refined to R P =0.084 in Pbca ( a =18.0241(1) A, b =13.9174(1) A and c =9.6554(1) A). The topology of AlPO-53(B), the tetrahedral equivalent of AlPO-EN3, is iso-structural with MCS-1 and UiO-12-500. This topology (structure type code AEN) has two 8-ring channels that intersect to form a 2D system. Heating AlPO 4 -53 to 700°C yields a new condensed phase, AlPO-53(C). The structure of AlPO-53(C) was solved with the FOCUS program and refined to R P =0.124 in C121 with a =16.4440(4) A, b =5.1075(1) A, c =13.4846(4) A, and β =88.259(1)°. AlPO-53(C) has a new topology described as brw nets in the ac plane, linked by single and double zigzag chains, parallel to b . The elliptical 8-ring pores, parallel to b , produce a 1D channel system. The highly distorted 4-, 6-, and 8-rings in AlPO-53(B) become more regular in AlPO-53(C). The thermal transformation of AlPO-53(B) to AlPO-53(C) is illustrated.

Neutron diffraction study of the zeolite thomsonite

Abstract A neutron study of a single crystal of thomsonite (Na(Ca,Sr) 2 Al 5 Si 5 O 20 .6H 2 O at 293K; a 13.088(2) b 13.052(2) c 13.229(2) A; Pncn) yielded a final agreement factor of R ( F 2 ) = 0.048 for conventional anisotropic refinement using 4626 diffraction intensities from the Brookhaven National Laboratory high-flux beam reactor. The SiO and AlO distances correlate inversely with SiOAl angle as in scolecite and edingtonite, and the scattering lengths for the tetrahedral nodes are consistent with alternation of Si and Al. Both sites for extra-framework cations are associated with elliptical 8-rings. The Na,Ca site contains 0.5 Na and 0.5 Ca, and is surrounded by a square antiprism containing 4 water-oxygens in one square (2.45, 2.50, 2.59, 2.60 A). Each square of water-oxygens is shared with an adjacent antiprism and one edge between framework-oxygens is shared with a second antiprism to give an infinite chain parallel to c. There is no evidence for long-range alternations of Na and Ca atoms. The Ca site is split into two positions displaced 0.28 A from the centroid of 6 framework-oxygens and 2 water-oxygens, and is coordinated to two framework-oxygens (2.44, 2.46 A) and two water-oxygens (2.34, 2.35 A) in a square and to two framework-oxygens (2.61, 2.65 A) on one side of the square. Some Sr may substitute in the Ca site. There is no evidence for ordered occupancy of Ca sites. All protons are in positions corresponding to electrostatic equilibrium. Those associated with Na,Ca lie close to the shared square, while those associated with Ca are almost coplanar with the cation and the water-oxygen. The distances from the proton to the water- and framework-oxygens are negatively correlated for edingtonite and thomsonite.

Quetzalcoatlite: A new octahedral-tetrahedral structure from a 2 × 2 × 40 μm3 crystal at the Advanced Photon Source-GSE-CARS Facility

Abstract The structure of quetzalcoatlite, Zn6Cu3(TeO3)2O6(OH)6(AgxPby)Clx+2y, x + y ≤ 2, Z = 1, was solved and refined using data collected at the Advanced Photon Source-GSE-CARS facility, using a 2 × 2 × 40 μm3 single crystal. The structure is trigonal, space group P3̅1m, a = 10.145(1), c = 4.9925(9) Å, V = 445.0(1) Å3, and was refined to R = 5.1 for 395 unique observed reflections. Te6+O6 octahedra and Jahn-Teller distorted Cu2+O4(OH)2 octahedra share edges to form layers parallel to (001), and ZnO2(OH)2 tetrahedra share vertices to form six-member rings parallel to (001). Layers of octahedra and tetrahedra alternate along c, and form a new framework structure by vertex sharing. Channels through the framework parallel to c are occupied by Ag, Pb, and Cl ions. Electron microprobe analysis revealed Ag and Cl overlooked in the original microchemical analysis. Up to one-third of the Ag was substituted by Pb, and a Pb-rich analog may exist.

Crystal Structure of Tetrabasic Lead Sulfate ( 4PbO ⋅ PbSO4 ) An Intermediate Phase in the Production of Lead‐Acid Batteries

Demand for improved battery systems for electric vehicles and power sources in general suggests the need for more accurate descriptions of the solid-state and electrochemical reactions which may affect active-material usage. Tetrabasic lead sulfate (4PbO.PbS0 4 ) is an intermediate phase commonly formed during production of lead-acid batteries and, with tribasic lead sulfate, determines some battery characteristics. Single-crystal X-ray data have been used to determine its structure to a final weighted R of 0.024 (a = 7.297, b = 11.698, and c = 11.498 A, = 90.93°, P2 1 /c). Its structure is closely related to that of tetragonal PbO, except that one of six Pb sites is occupied by SO 4 . This sulfate group shows either dynamic (librations) or static disorder, but there is no evidence in our crystal for Pb-S disorder as proposed by other X-ray studies. This determination and that for tribasic lead sulfate complete structural determinations of the major phases formed during production of lead-acid batteries. These structural models allow Rietveld studies using either X-ray or neutron-diffraction data to evaluate properties such as crystallinity, atomic ordering, and reactions during curing and cycling. The structures of tetrabasic and tribasic lead sulfate, as well as tetragonal and orthorhombic PbO, have basic features in common. These similarities suggest that there may be structural control during some reactions whereby heterogeneous nucleation influences the products in concert with external variables such as temperature, humidity, and pH.

Neutron diffraction study of zoisite at 15 Κ and X-ray study at room temperature

The crystal structure of zoisite, Ca2Al3Si30i20H; Pnma, Ζ = 4, was determined for crystals of the tanzanite gem variety at 15 Κ (neutron diffraction, a = 16.218(3), b = 5.5406(14), c = 10.033(3) Ä) and room temperature, ~ 295 Κ (X-ray diffraction, a = 16.1909(15), b = 5.5466(5), c = 10.0323(6) A). Only one proton position was located with positional coordinates 0.2690(1), 0.25, 0.9753(2) and population factor 0.98(1) at 15 K. It forms a hydroxyl group with 0(10) at 0.986(2) A and a hydrogen bond with 0(4) at 1.757(2) A. There is no diffraction evidence of a second proton position to explain the weak infrared absorption at 2160 cm 1 at room temperature for both natural and synthetic zoisites; however, the detection level of 0.01 atom at the 2 σ level might be insufficient. The possibility of hydrogen bonding to two 0(2) at 2.96 A from O(IO) is discussed. Because the displacement ellipsoid of the proton at 15 Κ is oblate and smaller than the ones in staurolite, it is concluded that there is only a single center of motion of the proton. The wide ranges of Ca—Ο, Al—Ο and Si—Ο distances are consistent with valence balancing in which short * Joint appointment with the Intense Pulsed Neutron Source Division, Argonne National Laboratory, Argonne, IL 60439, USA. 306 J. V. Smith, J . J . Pluth, J . W. Richardson, Jr. and Ä. Kvick distances go to oxygen atoms with low values of formal bond strength. The displacement ellipsoids at 295 Κ can be explained qualitatively by anisotropic thermal motion constrained by the bonding to the nearest neighbors. There is an additional overall anisotropy at 15 Κ which is unexplained. However, values of Biia are consistent with zero-point motion, and there is no evidence for positional disorder.

CRYSTAL STRUCTURE OF MACPHERSONITE (PB4SO4(CO3)2(OH)2) : COMPARISON WITH LEADHILLITE

Abstract The crystal structure of macphersonite (Pb4SO4(CO3)2(OH)2, Pcab, a = 9.242(2), b = 23.050(5), c = 10.383(2) Å) from Leadhills, Scotland has been determined to an R = 0.053. The structure has many features in common with its polymorph leadhillite including three distinct types of layers. Layer A includes sulphate tetrahedra, Layer B is composed of Pb and OH, while Layer C is composed of Pb and CO3 with topology identical to that in cerussite. In both macphersonite and leadhillite these layers are stacked along [010] as ...BABCCBABCC... The double CC layer is almost identical in the two structures and forms a structural backbone and occurs in other structures including hydrocerussite and plumbonacrite. The sulphate layer shows the greatest difference between the two structures and can be described by a pattern of up or down pointing tetrahedra. For macphersonite the sequence along [001] is ...UDUDUD... while in leadhillite the sequence along [010] is ...UDDUUDDU... This latter sequence effectively doubles b relative to the equivalent direction in macphersonite. Susannite, a third polymorph, may have yet another sequence of sulphates to give trigonal symmetry; by heating leadhillite, displacive movements of sulphate groups may occur with a conversion to susannite.

Crystal structure refinement of miargyrite, AgSbS 2

Abstract Miargyrite is the low-temperature monoclinic derivative of a high-temperature cubic galena/halite structure. The essential features of its crystal structure (Knowles, 1959) were confirmed, but the details of the bonding changed [new space group C121; a 12.824(1), b 4.4060(3), c 13.193(1) Å, β 98.567(6)°]. The octahedral connectivity of galena/halite is severely distorted: Ag(1), 2S each at 2.53, 2.66 & 3.39 Å; Ag(2), 2 each at 2.54, 2.62 and 3.44; Ag(3), 2.38, 2.40, 3.05, 3.05, 3.53, 3.58; Sb(1), 2.45, 2.50, 2.51, 3.22, 3.28, 3.41; Sb(2), 2.45, 2.50, 2.51, 3.22, 3.28, 3.41. The short distances define the following coordinations: very distorted tetrahedral Ag(1) and (2); near-linear Ag(3) at 178.9(2)° trigonal-pyramidal Sb(1) and (2) at 92.0, 93.6 and 96.8°. The ten shortest S-S distances range from 3.61 to 3.77 Å.