scholarly journals Simple Method for Estimating the Contribution of Neighbouring n-beam Interactions to Two-beam Structure Factors

1988 ◽  
Vol 41 (3) ◽  
pp. 469
Author(s):  
HJ Juretschke ◽  
HK Wagenfeld
Keyword(s):  
Experimental Determination ◽  
Structure Factor ◽  
Beam Structure ◽  
Simple Method ◽  
Experimental Configuration ◽  
Structure Factors ◽  
Special Cases ◽  
Better Than

Unless special precautions are taken, the experimental determination of two-beam structure factors to better than 1 % may include contributions from neighbouring n-beam interactions. In any particular experimental configuration, corrections for such contributions are easily carried out using the modified two-beam structure factor formalism developed recently (Juretschke 1984), once the full indexing of the pertinent n-beam interactions is known. The method is illustrated for both weak and strong primary reflections and its applicability in special cases, as well as for less than perfect crystals, is discussed.

Obtaining the structure factors for an epitaxial film using Cu X-ray radiation

2013 ◽  
Vol 46 (6) ◽  
pp. 1749-1754 ◽  
Author(s):  
P. Wadley ◽  
A. Crespi ◽  
J. Gázquez ◽  
M.A. Roldán ◽  
P. García ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Thin Films ◽  
Structure Factor ◽  
Tetragonal Symmetry ◽  
X Ray Diffraction ◽  
X Ray ◽  
Transmission Electron ◽  
Structure Factors ◽  
Scanning Transmission

Determining atomic positions in thin films by X-ray diffraction is, at present, a task reserved for synchrotron facilities. Here an experimental method is presented which enables the determination of the structure factor amplitudes of thin films using laboratory-based equipment (Cu Kα radiation). This method was tested using an epitaxial 130 nm film of CuMnAs grown on top of a GaAs substrate, which unlike the orthorhombic bulk phase forms a crystal structure with tetragonal symmetry. From the set of structure factor moduli obtained by applying this method, the solution and refinement of the crystal structure of the film has been possible. The results are supported by consistent high-resolution scanning transmission electron microscopy and stoichiometry analyses.

THE THERMAL CONDUCTIVITY OF NAPALM–GASOLINE GELS

1948 ◽  
Vol 26a (2) ◽  
pp. 50-59 ◽  
Author(s):  
G. O. Langstroth ◽  
F. Zeiler
Keyword(s):  
Thermal Conductivity ◽  
Temperature Coefficient ◽  
Small Diameter ◽  
Temperature Coefficient Of Resistance ◽  
Simple Method ◽  
Viscous Liquids ◽  
Low Viscosity ◽  
Tungsten Filaments ◽  
Better Than

A slightly modified form of the rapid and simple method suggested by Hutchinson for the measurement of the thermal conductivity of liquids has been found to suffer from convection effects with samples of low viscosity, except with conductivity tubes of very small diameter. For more viscous liquids such as glycerol it was found to be adequate under all conditions studied. The method has been applied in the determination of the conductivity of Napalm–gasoline gels. For temperatures T between − 50° and 50 °C., and Napalm concentrations C between 0 and 10%, the conductivity k in cal. sec.−1 cm.−1 per degree C. is described to better than 1% by the relation, k × 105 = 29.7 − 0.068 T + 0.11 C. The temperature coefficient of resistance of the unaged tungsten filaments used in the tubes differed considerably from the value given by the International Critical Tables for aged tungsten filaments. For temperatures T0 between − 50° and 50 °C., the coefficient α0 per degree C. is given to better than 1% by the relation, [Formula: see text].

The HLM method: a simple way to get the solid–liquid phase diagrams and enthalpies of transition of pure components and mixtures

1992 ◽  
Vol 70 (11) ◽  
pp. 2745-2750 ◽  
Author(s):  
François Quirion ◽  
Daniel Lambert ◽  
Gérald Perron
Keyword(s):  
Differential Scanning Calorimetry ◽  
Chemical Engineering ◽  
Low Cost ◽  
Polymer Science ◽  
Scanning Calorimetry ◽  
Simple Method ◽  
Melting Temperatures ◽  
Solid Liquid ◽  
Better Than

A simple method of thermal analysis is described which gives the same information as differential scanning calorimetry. The method is based on the Heat-Leak-Modulus, HLM, of a sample cell placed in a constant temperature reservoir. In the present study, the HLM method is used for the investigation of pure components and mixtures from −190 to 50 °C. The method allows the determination of glass-transition, crystallizations, solid–solid transition, eutectic, and melting temperatures with a reproducibility better than ±0.1 °C. The enthalpy of a transition can be determined with a reproducibility of ±5%. The simplicity, the low cost, and the precision of the HLM method fills the gap between standard cooling curves and sophisticated differential scanning calorimetry experiments. The HLM method has numerous applications in physical chemistry, polymer science, metallurgy, and chemical engineering.

Deconvolution of the Lorentzian Linewidth and Determination of Fraction Lorentzian Character from the Observed Profile of a Raman Line by a Comparison Technique

1982 ◽  
Vol 36 (3) ◽  
pp. 250-257 ◽  
Author(s):  
B. P. Asthana ◽  
W. Kiefer
Keyword(s):  
Experimental Determination ◽  
Raman Line ◽  
Good Accuracy ◽  
Half Maximum ◽  
Difference Spectroscopy ◽  
Simple Method ◽  
Spectrometer Slit ◽  
The Given ◽  
Comparison Technique

We report on a simple method to derive the Lorentzian linewidth of a Raman line as well as its fraction Lorentzian character. The method is based on the experimental determination of the bandwidths at half maximum obtained from recorded Raman and plasma lines with same spectrometer slit settings. From the ratio of the two half bandwidths, the Lorentzian Raman linewidth can be easily derived from the given table. This table was compiled by explicit calculations of Voigt profiles. The fraction Lorentzian character, needed for instance for Raman difference spectroscopy, can be obtained directly from this table to a good accuracy.

Experimental determination of low order structure factors in the intermetallic compound TiAl

1993 ◽  
Vol 170 (1-2) ◽  
pp. 227-235 ◽  
Author(s):  
S. Swaminathan ◽  
I.P. Jones ◽  
N.J. Zaluzec ◽  
D.M. Maher ◽  
H.L. Fraser
Keyword(s):  
Intermetallic Compound ◽  
Experimental Determination ◽  
Order Structure ◽  
Structure Factors ◽  
Compound Tial ◽  
Low Order

Mechanical and Electrical Run-Out Removal on a Precision Rotor-Vibration Research Spindle

1997 ◽  
Vol 119 (2) ◽  
pp. 216-220 ◽  
Author(s):  
G. A. Horattas ◽  
M. L. Adams ◽  
F. Dimofte
Keyword(s):  
Steady State ◽  
Experimental Determination ◽  
Journal Bearing ◽  
Dynamic Performance ◽  
Data Acquisition System ◽  
Small Range ◽  
Rotor Vibration ◽  
System 1 ◽  
Better Than

Experimental determination of both steady-state and dynamic performance of a journal bearing requires the use of a high precision spindle with a vanishingly small range of run-out. This was achieved by first eliminating the mechanical run-out of the spindle by grinding the journal specimen while rotating in place. Once the mechanical run-out was removed, the electrical run-out sensed by the displacement proximity-probe-transducers was also removed. Using this procedure the mechanical and electrical run-outs of a research spindle were reduced to less than 0.2 micron (10 μin.), which is better than the resolution of the data acquisition system, 1 micron (50 μin.).

scholarly journals Concerning Single Crystal Reflectivity Curves

1988 ◽  
Vol 41 (3) ◽  
pp. 393
Author(s):  
A McL Mathieson
Keyword(s):  
Single Crystal ◽  
Experimental Evidence ◽  
Structure Factor ◽  
Bragg Reflection ◽  
Half Maximum ◽  
Reflectivity Curve ◽  
One Dimensional ◽  
Structure Factors ◽  
Kinematical Limit

The extinguished reflectivity curve of a Bragg single crystal reflection represents the basic experimental evidence for the determination of accurate structure factors. In normal measurement procedures of one-dimensional (ID) 'counter' profiles, information on such curves is obscured by the presence of other, more dominant components. It is therefore difficult to separate out these curves so that a realistic correction for extinction can be applied. By considering the 'shape' of a Bragg reflection in the plane of diffraction from the ~w, ~2e viewpoint, procedures have been deduced for practical zero wavelength dispersion measurement of reflectivity curves for virtually any e value and, with these curves, corrections can be applied to produce extinction-free structure factor values. Attention is drawn to the fact that the width of the experimental reflectivity curve (say at half maximum) can provide a valuable criterion to assist in attaining the 'kinematical limit'.

scholarly journals Non-systematic Three-beam Effects in Dynamical Electron Diffraction and Their Use in Determination of Amplitude and Phase of Structure Factors

1988 ◽  
Vol 41 (3) ◽  
pp. 449 ◽  
Author(s):  
K Marthinsen ◽  
H Matsuhata ◽  
R Hfier ◽  
J Gjfnnes
Keyword(s):  
Electron Diffraction ◽  
Structure Factor ◽  
Bloch Wave ◽  
Critical Voltage ◽  
Dispersion Surface ◽  
Structure Factors ◽  
Three Phase ◽  
Convergent Beam ◽  
Diffraction Condition

The treatment of non-systematic multiple-beam effects in dynamical diffraction is extended. Expressions for Bloch wave degeneracies are given in the centrosymmetrical four-beam case and for some symmetrical directions. These degeneracies can be determined experimentally either as critical voltages or by locating the exact diffraction condition at a fixed voltage. The accuracy when applied to structure factor determination is comparable with the systematical critical voltage, namely 1% in UfT The three-beam case 0, g, h is treated as well in the non-centrosymmetrical case, where it can be used for determination of phases. It is shown that the contrast features can be represented .by an effective structure factor defined by the gap at the dispersion surface. From the variation in the gap with diffraction condition, a method to determine the three-phase structure invariant I\J = 9 + _ h + h _ 9 is given. The method is based upon the contrast asymmetry in the weaker diffracted beam and can be applied in Kikuchi, convergent beam or channelling patterns. Calculations relating to channelling in backscattering are also presented.

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