Variation in P-O Bonding in Phosphate Glasses -A Neutron Diffraction Study

2000 ◽  
Vol 55 (3-4) ◽  
pp. 369-380 ◽  
Author(s):  
Uwe Hoppe ◽  
Rainer Kranold ◽  
Dörte Stachel ◽  
Andrea Barz ◽  
Alex C. Hannonb
Keyword(s):  
Neutron Diffraction ◽  
Large Range ◽  
Glass Composition ◽  
Neutron Diffraction Study ◽  
Real Space ◽  
Phosphate Glasses ◽  
Bond Lengths ◽  
Modifier Cation ◽  
The Mean ◽  
Oxygen Atoms

Two different lengths of P-O bonds in the PO4 units of phosphate glasses are found by neutron diffraction experiments of high resolution in real space. The two lengths are related to bonds of the phosphorus atom with the terminal and the bridging oxygen atoms. The mean lengths and widths of both P-0 distance peaks change as a function of the glass composition. In a large range, starting from vitreous P2O5 s up to the pyrophosphate composition, the behavior of the bond lengths is compared with that in the related crystals and with that resulting from ab initio calculations. The bond lengths depend not only on the species of the participating oxygen atoms and on the number of links of the concerning PO4 unit but also on the number of links of the neighboring PO4 unit and on the species of the modifier cation

Neutron diffraction investigation of copper tellurite glasses with high real-space resolution

2021 ◽  
Vol 54 (6) ◽  
Author(s):  
Navjot Kaur ◽  
Atul Khanna ◽  
Alex C. Hannon
Keyword(s):  
Neutron Diffraction ◽  
Coordination Number ◽  
Diffraction Data ◽  
Fourier Transformation ◽  
Short Range ◽  
Real Space ◽  
Tellurite Glasses ◽  
Space Resolution ◽  
Bond Lengths ◽  
Structure Factors

High real-space resolution neutron diffraction measurements up to 34 Å−1 were performed on a series of xCuO–(100 − x)TeO2 (x = 30, 40 and 50 mol%) glasses that were synthesized by the melt-quenching technique. The Fourier transformation of neutron diffraction structure factors was used to generate the pair distribution functions, with the first peak at 1.90 Å due to the overlapping Te–O and Cu–O atomic pairs. Reverse Monte Carlo (RMC) simulations were performed on the structure factors and the six partial atomic pair distributions of Cu–Cu, Cu–Te, Cu–O, Te–Te, Te–O and O–O were calculated. The Te–O and Cu–O distributions are very similar and asymmetrical, which revealed that there is a significant short-range disorder in the tellurite network due to the existence of a wide range of Te—O and Cu—O bond lengths. A high-Q (magnitude of momentum transfer function) neutron diffraction study revealed that the average Te–O coordination number decreases steadily from 3.45 to 3.18 with an increase in CuO concentration from 30 to 50 mol% in the glass network. Similar coordination number modifications were earlier found by the RMC analysis of neutron diffraction data sets of copper tellurite glasses that were performed up to lower Q maximum values of 9.5 Å−1. The comparison of high-Q and low-Q neutron diffraction studies reveals that RMC is a powerful and possibly the only technique that is available to elucidate the glass short-range and medium-range structural properties when diffraction data are available up to low Q values of, say, 9.5 Å−1, and when cation–oxygen bond lengths are strongly overlapping and cannot be resolved by Fourier transformation. In situ high-temperature (473 K) neutron diffraction studies of 50CuO–50TeO2 glass revealed that significant distortion of the tellurite network occurs with heating.

21.—Riding Motion and Higher Cumulants in Crystallographic Models

1972 ◽  
Vol 70 ◽  
pp. 225-232
Author(s):  
G. S. Pawley
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Neutron Diffraction Study ◽  
High Accuracy ◽  
Vibrational Modes ◽  
Diffraction Experiment ◽  
Hydrogen Atoms ◽  
Curvilinear Motion ◽  
Higher Order Terms ◽  
The Mean

SynopsisThe motion of hydrogen atoms due to the internal vibrational modes of a molecule is large and curvilinear. Because of the curvilinear motion the mean displacements of these atoms cannot be described by ellipsoids alone, but higher order terms or cumulants are necessary. Equations determining these terms from the usual riding motion are presented. By analysing a neutron diffraction study of high accuracy it is shown that the size of these higher cumulants is sufficient for them to be determinable. For deuterated samples however really high accuracy will be necessary in the diffraction experiment.

A neutron diffraction study of mercury(II)chromate hemihydrate, HgCrO4 · 1/2 H2O

1975 ◽  
Vol 142 (3-4) ◽  
Author(s):  
Karin Aurivillius ◽  
Claes Stålhandske
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Water Molecule ◽  
Diffraction Study ◽  
Neutron Diffraction Study ◽  
Mercury Atom ◽  
Building Elements ◽  
Oxygen Atoms

AbstractThe crystal structure of mercury(II)chromate hemihydrate, HgCrOThe mercury atom is bonded only to two oxygen atoms, each belonging to a separate Chromate tetrahedron, at the distances 2.055(2) and 2.064(2) Å, the angle O–Hg–O being 179.95(5)°. As each Chromate group is bonded to two mercury atoms, fundamental building elements of the structure are endless chains of the composition (HgCrOIn the water molecule the distances O(W)–H (2 × ) and H–H are 0.945(4) and 1.487(6) Å respectively. The angle H–O(W)–H is 103.7(4)°. In the hydrogen bonds the distance O(W)–H…O between water and Chromate oxygen atoms is 2.961(2) Å with a distance H…O of 2.133(4) Å and an angle O(W)–H…O of 145.6(3)°.

The crystal structure of deuterated benzene

1987 ◽  
Vol 414 (1846) ◽  
pp. 47-57 ◽  
Keyword(s):  
Crystal Structure ◽  
Neutron Diffraction ◽  
Molecular Orbital Calculations ◽  
Bond Lengths ◽  
M 10 ◽  
Cell Dimensions ◽  
Experimental Errors ◽  
The Mean ◽  
Unit Cell Dimensions ◽  
Deuterated Benzene

The crystal structure of deuterated benzene has been refined by single-crystal neutron diffraction analysis at 15 and 123 K. The unit-cell dimensions were also measured at 52.6 and 80 K, and the thermalexpansion coefficients at all four temperatures were calculated. The molecules have C 3v symmetry with a small chair-distortion from D 6h , which is possibly significant for the carbon atoms and significant for the deuterium atoms. The mean observed bond lengths at 15 K [123 K] are C-C = 1.3972(5) Å [1.3940(9) Å] (1 Å = 10 -10 m = 10 -1 nm); C-D = 1.0864(7) Å [1.0838(10) Å]. When corrected for molecular libration, the corresponding rest values are 1.3980 Å [1.3985 Å]; 1.088 Å [1.088 Å]. Ab initio molecular orbital calculations at the MP-2/6-31G* level gave energy-optimized bond lengths of 1.395 and 1.087 Å for the isolated molecule at rest, in agreement with the corrected values from the crystal structure within the experimental errors.

The Crystal Structure of KAlP2O7

1973 ◽  
Vol 51 (16) ◽  
pp. 2613-2620 ◽  
Author(s):  
Hok Nam Ng ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Spherical Shell ◽  
Bond Length ◽  
Least Squares ◽  
Least Squares Method ◽  
Full Matrix ◽  
Bond Lengths ◽  
The Mean ◽  
R Value ◽  
Oxygen Atoms

KAlP2O7 crystallizes as monoclinic crystals with a = 7.308(8), b = 9.662(6), c = 8.025(4) Å, β = 106.69(7)°, z = 4 and space group P21/c. The structure was refined from 1394 observed reflections by full-matrix least-squares method to a final R value of 0.032. The P2O74− anion consists of a pair of corner-sharing PO4 groups in a nearly staggered configuration. The mean bridging and terminal P—O bond lengths are 1.607 and 1.509 Å, respectively, and the P—O—P angle is 123.2°. The anions lie in planes parallel to (001). The Al ions are bonded to six oxygen atoms contributed by anions in three layers of P2O7 groups. The average Al—O bond length is 1.889 Å. The potassium ion is coordinated to ten oxygen atoms lying within a spherical shell with inner and outer radii of 2.739 and 3.185 Å.

scholarly journals A Neutron and X-ray Diffraction Study of the Structure of Nd Phosphate Glasses

2001 ◽  
Vol 56 (3-4) ◽  
pp. 237-243 ◽  
Author(s):  
Uwe Hoppe ◽  
Heike Ebendorff-Heidepriem ◽  
Jörg Neuefeind ◽  
Daniel T. Bowron
Keyword(s):  
Neutron Diffraction ◽  
Diffraction Study ◽  
Coordination Number ◽  
Diffraction Data ◽  
Phosphate Glasses ◽  
Neutron Diffraction Data ◽  
X Ray Diffraction ◽  
X Ray ◽  
Oxygen Atoms

Abstract Diffraction experiments were performed on two (Nd2O3)x(P2O5)1- x glasses for studying the en­ vironmental order of the Nd3+ cations. In case of the metaphosphate glass (x = 0.25) a combination of X-ray and neutron diffraction data was used to separate the Nd-O and O-O first neighbor peaks. An Nd-O coordination number of 6.6±0.3 and a mean Nd-O distance of (0.239±0.001) nm were determined. In the ultraphosphate glass studied (x = 0.20) these values increase to 6.9±0.3 and (0.240±0.001) nm where the Nd-0 coordination number is equal to the number of terminal oxygen atoms (OT) which are available for coordination of each Nd3+ cation. This indicates the formation of NdOn polyhedra not sharing any O atom where also all OT's are in N d-OT-P positions. In the metaphosphate glass the NdOn polyhedra have to share some OT sites.

scholarly journals Crystal structure of CaK2As2O7 and CdK2P2O7

1976 ◽  
Vol 54 (21) ◽  
pp. 3319-3324 ◽  
Author(s):  
Romolo Faggiani ◽  
Crispin Calvo
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Coordination Sphere ◽  
Divalent Cations ◽  
Lattice Parameters ◽  
Full Matrix ◽  
Space Group ◽  
Bond Lengths ◽  
The Mean ◽  
Oxygen Atoms

Crystals of CaK2As2O7 and CdK2P2O7, both grown from the melt, are monoclinic with Z = 4. The lattice parameters are a = 9.222(6), b = 5.835(3), c = 14.698(10) Å, β = 105.84(5)° with space group P21/c for the diarsenate and a = 9.737(2), b = 5.548(1), c = 12.766(2) Å, β = 106.50(2)° with space group C2/c for the diphosphate. The structures were refined by full-matrix least-squares methods utilizing 2070 reflections (R = 0.056) for the diarsenate and 1145 reflections (R = 0.067) for the diphosphate. Both structures contain pseudo-hexagonally packed anions, in staggered configurations, forming layers with the divalent cations in six coordinate sites between the layers. The average M—O bond lengths are 2.342 and 2.290 Å for M = Ca and Cd respectively. The K ion has nine oxygen atoms with mean K—O bond lengths of 2.943 and 3.020 Å in the diarsenate in the coordination sphere. The mean of the ten shortest K—O is 2.939 Å in the diphosphate.

The P-O bond lengths in vitreous probed by neutron diffraction with high real-space resolution

1998 ◽  
Vol 10 (2) ◽  
pp. 261-270 ◽  
Author(s):  
U Hoppe ◽  
G Walter ◽  
A Barz ◽  
D Stachel ◽  
A C Hannon
Keyword(s):  
Neutron Diffraction ◽  
Real Space ◽  
Space Resolution ◽  
Bond Lengths

Location of the proton in the very strong OHO hydrogen bonds in 2-(N,N-diethylamino-N-oxymethyl)-4,6-dichlorophenol. A single crystal neutron diffraction study

1997 ◽  
Vol 212 (2) ◽  
Author(s):  
H. Ptasiewicz-Bak ◽  
R. Tellgren ◽  
I. Olovsson ◽  
A. Koll
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bond ◽  
Hydrogen Bonds ◽  
Neutron Diffraction ◽  
Single Crystal ◽  
Diffraction Study ◽  
Neutron Diffraction Study ◽  
Crystallographic Symmetry ◽  
O 175.8 ◽  
Oxygen Atoms

AbstractThe crystal structure of 2-(N,N-diethylamino-N-oxymethyl)-4,6-dichlorophenol contains two slightly different molecules A and B, both with very strong intramolecular O … H … O hydrogen bonds, with O–O distances 2.423(4) Å and 2.400(5) Å, respectively, and with no crystallographic symmetry. The bridging oxygen atoms are also chemically different, O1 is bonded to carbon and O2 to nitrogen. The single crystal neutron diffraction study shows quite unambiguously that the proton in both cases is located slightly off-centred. In the A molecule O1–H = 1.167(6) Å, H–O2 = 1.258(6) Å and the angle O–H–O = 175.8(5)°; in the B molecule O1–H = 1.186(7) Å, H–O2 = 1.214(7) Å and the angle O–H–O = 176.5(5)°. As expected the proton is thus closer to the centre in the slightly shorter hydrogen bond.

The crystal structure of kintoreite, PbFe3(PO4)2(OH,H2O)6

1997 ◽  
Vol 61 (404) ◽  
pp. 123-129 ◽  
Author(s):  
Kharisu ◽  
M. R. Taylor ◽  
D. J. M. Bevan ◽  
A. Pring
Keyword(s):  
Crystal Structure ◽  
Type Structure ◽  
Coordination Polyhedra ◽  
Bond Lengths ◽  
The Mean ◽  
Oxygen Atoms

AbstractThe crystal structure of kintoreite, PbFe3(PO4)2(OH,H2O)6, has been refined. The mineral is rhombohedral, Rm with a = 7.3310(7), c = 16.885(2) Å, Z = 3; the structure has been refined to R = 3.0% and Rw = 3.0% using 183 observed reflections [I > 2σ(I)]. Kintoreite has the alunite-type structure which consists of sheets of corner-sharing Fe(O,OH)6 octahedra parallel to (001). The sheets are composed of clusters of three corner-linked octahedra which are tilted so that the three apical O atoms form the base of the XO4 tetrahedra. The clusters of octahedra are linked to similar groups by corner-sharing to form six membered rings. The Pb cations occupy the cavities between pairs of octahedral sheets and are surrounded by six oxygen atoms from the tetrahedra and six oxygen atoms from the octahedra to form a very distorted icosahedron. The mean bond lengths for the various coordination polyhedra are X–O 1.55 Å, (X= P, As, S); Fe–(O, OH) 2.01 Å; Pb–O 2.84 Å. The composition of the crystal used in the refinement was PbFe3(PO4)1.3(AsO4)0.4(SO4)0.3(OH,H2O)6. The XO4 anions are disordered, as in beudantite, rather than being ordered, as they are claimed to be in corkite.

Sign in / Sign up

Export Citation Format

Share Document