Crystal structure study of a β′-copper vanadium bronze, Cu x V2O5 (x = 0.63), by X-ray and convergent beam electron diffraction

2005 ◽  
Vol 61 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Victor A. Streltsov ◽  
Philip N. H. Nakashima ◽  
Alexandre N. Sobolev ◽  
Ruslan P. Ozerov
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Structure Study ◽  
Convergent Beam Electron Diffraction ◽  
Convincing Evidence ◽  
Dynamic Nature ◽  
Beam Electron ◽  
X Ray ◽  
Structure Changes ◽  
Convergent Beam

The single-crystal structure of a β′-copper vanadium bronze, Cu0.63V2O5, has been studied at room temperature and 9.6 K, and compared with that of the β-sodium vanadium bronze, Na0.33V2O5, structure. No convincing evidence to oppose an assignment of centrosymmetric C2/m symmetry to the structure was identified using the X-ray data. A subsequent convergent beam electron diffraction (CBED) experiment was performed and confirmed the C2/m space group. The oxygen–vanadium atom framework of Cu0.63V2O5 is close to that of Na0.33V2O5. However, in the copper compound the Cu atoms are located in two positions: Cu1 in the 4(i) position with x = 0.541, y = 0 and z = 0.345, and Cu2 in the 8(j) position with x = 0.529, y = 0.038 and z = 0.357. The crystal structure changes little with temperature. Disorder of the Cu ion over two sites is seen at 9.6 K. This suggests that distribution of the Cu atoms over two sites is of a more static than dynamic nature.

Crystal structure determination by convergent-beam electron diffraction

1989 ◽  
Vol 47 ◽  
pp. 476-477
Author(s):  
R. Vincent ◽  
D. J. Exelby
Keyword(s):  
Crystal Structure ◽  
Electron Diffraction ◽  
Structure Determination ◽  
Convergent Beam Electron Diffraction ◽  
Crystal Structure Determination ◽  
Large Set ◽  
Beam Electron ◽  
X Ray ◽  
Structure Factors ◽  
Convergent Beam

In recent years, significant progress has been made towards a solution for the general problem of crystal structure determination by convergent beam electron diffraction (CBED). Even if we consider only perfectly ordered, periodic crystals defined by one of the conventional space groups, diffraction methods based on a focussed sub-micron beam of electrons are applicable to several related sets of structural problems that are not accessible to conventional X-ray or neutron diffraction techniques. We assume here that the space group either is known or has been determined from CBED patterns and that phases and amplitudes for some subset of the structure factors are required. Two limiting cases have been explored in some detail. For crystals where the atomic parameters and Debye-Waller factors are known accurately from high quality X-ray data, information on the charge redistribution for bonding electrons is available from precise measurements of the low order structure factors. Following the original research of Kambe, some recent work has demonstrated that accurate structure amplitudes and three-beam phase invariants can be extracted from the dynamical intensity distribution in CBED reflections. In principle, this approach is completely general but considerable labour would be required to extract sufficient data to solve the structure of an unknown crystal, whereas a large set of kinematic intensities is acquired from a single X-ray pattern.

scholarly journals Influence of Doping on the Crystal Potential of Silicon investigated by the Convergent Beam Electron Diffraction Technique

1980 ◽  
Vol 35 (9) ◽  
pp. 973-984 ◽  
Author(s):  
R. Voss ◽  
G. Lehmpfuhl ◽  
P. J. Smith
Keyword(s):  
Electron Diffraction ◽  
Excellent Agreement ◽  
Convergent Beam Electron Diffraction ◽  
Index Structure ◽  
Beam Electron ◽  
X Ray ◽  
Crystal Potential ◽  
Small Crystal ◽  
Electron Diffraction Technique ◽  
Convergent Beam

Abstract Low index structure potentials of silicon were determined by convergent beam electron diffraction (Kossel-Möllenstedt technique) from very small crystal areas of about 100 Å in diameter. The values of 111, 222, 220, 113 and 004, determined to an accuracy of ±0.03 volts, are in excellent agreement with the accurate X-ray results of Aldred and Hart (see [6], p. 239). Heavy arsenic or phosphorous doping was found to cause a shift of 0.15 volts in the 111 structure potential. Absorption potentials were also determined and found to be 1/3 of the theoretical values published by Radi [20].

Thickness dependence of the intensities of the 200 forbidden reflections in the TiBe2 diamond type structure

1988 ◽  
Vol 46 ◽  
pp. 826-827
Author(s):  
Dang-Rong Liu ◽  
D. B. Williams
Keyword(s):  
Electron Diffraction ◽  
Diffraction Pattern ◽  
Convergent Beam Electron Diffraction ◽  
Type Structure ◽  
Beam Electron ◽  
Space Group ◽  
X Ray ◽  
Electron Diffraction Technique ◽  
Convergent Beam ◽  
Diamond Type

It is interesting to note that for the diamond type structure of Si, Ge and diamond, the forbidden {200} reflections in the exact <100> orientation diffraction pattern cannot be seen. In contrast, we also note a standing controversy over the structure of the MgAl2O4, spinel. Its structure was determined long ago by x-ray powder method as Fd3m (the diamond type). However, its electron diffraction pattern taken in the <100> orientation shows weak {200} reflections, which are taken as evidence that the spinel should have the space group F43m (the blende type), rather than Fd3m. Others speculate that these {200} reflections result from the high order Laue zone (HOLZ) reflections, and the spinel should be Fd3m. Nevertheless, still others think that these analyses are not conclusive. We have carefully studied the space group of TiBe2 using the convergent beam electron diffraction technique, and unambiguously demonstrated that its space group must be Fd3m.

Dislocations in YBa2Cu3O7−δ (δ = 0.77)

1990 ◽  
Vol 48 (4) ◽  
pp. 72-73
Author(s):  
Yimei Zhu ◽  
Hong Zhang ◽  
A.R. Moodenbaugh ◽  
M. Suenaga
Keyword(s):  
Electron Microscope ◽  
Electron Diffraction ◽  
Displacement Vector ◽  
Stacking Faults ◽  
Spot Size ◽  
Convergent Beam Electron Diffraction ◽  
Burgers Vector ◽  
Beam Electron ◽  
X Ray ◽  
Convergent Beam

Abundant dislocations and dislocations associated with stacking faults were observed and characterized in YBa2Cu3O7−δ (δ= 0.77). The crystallographic orientation of the dislocation and the fault were analyzed using Kikuchi patterns matched with computer generated Kikuchi maps. The Burgers vector of the dislocation and the displacement vector of the fault were determined by using the g·b = 0 and g · R=0 criteria.Bulk samples of YBa2Cu3O7 were produced by standard pressing and sintering up to 970 °C. Samples were heated in air, then quenched into liquid nitrogen to reduce oxygen content. Subsequent anneal at 200 ° C took place with samples sealed in silica with 1/2 atm. of argon. TEM specimens were thinned by ion mill and examined in a JEOL 2000FX electron microscope operating at 200kv.X-ray powder diffraction and convergent beam electron diffraction with 200 Å spot size show that YBa2Cu3O6.23 has a tetragonal structure.

Measurement of Debye-Waller factors of silicon as a function of temperature using energy-filtered CBED rocking-curve technique

1994 ◽  
Vol 52 ◽  
pp. 996-997
Author(s):  
S. Swaminathan ◽  
S. Altynov ◽  
I. P. Jones ◽  
N. J. Zaluzec ◽  
D. M. Maher ◽  
...  
Keyword(s):  
Electron Diffraction ◽  
Liquid Nitrogen Temperature ◽  
Convergent Beam Electron Diffraction ◽  
Higher Order ◽  
X Ray Diffraction ◽  
Beam Electron ◽  
X Ray ◽  
Crystal Potential ◽  
Transmission Electron ◽  
Convergent Beam

The advantages of quantitative Convergent Beam Electron Diffraction (CBED) method for x-ray structure factor determination have been reviewed by Spence. The CBED method requires accurate values of Debye-Waller (D-W) factors for the estimation of the coefficients of crystal potential of the higher order beams, Vg, the calculation of the absorption potential, V′g using the Einstein model for phonons, and finally the conversion of the fitted values of the coefficients of crystal potential, V″, to x-ray structure factors. Debye-Waller factors are conventionally determined by neutron or x-ray diffraction methods. Because of the difficulties in conducting high temperature neutron and x-ray diffraction experiments, D-W factors are rarely measured at temperatures above room temperature. Debye-Waller factors at high temperatures can be determined by Convergent Beam Electron diffraction (CBED) method using Transmission Electron Microscopy (TEM) employed with a hot stage attachment. Recently Holmestad et al. have attempted to measure the D-W factors by matching the energy-filtered Higher Order Laue Zone (HOLZ) line intensities near liquid nitrogen temperature.

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