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National Advisory Committee for Aeronautics, Technical Notes - Table of Interplanar Spacings for Crytal Structure Determinations by X-Ray Diffraction with Molybdenum, Copper, Cobalt, Iron, and Chromium Radiators

A widely used technique in X-ray-diffraction investigations
consists in placing a powdered or small polycrystalline specimen
in a Debye- Scherrer camera and allowing .a beam of monochromatic
X—rays to fall upon the specimen. A fraction of this primary
beam of X-rays will be diffracted by the specimen. The diffracted
rays leave the specimen in the form of cones, the axes of which
-are identical with the primary X-ray beam. The cones of dif-
fracted X-rays, if allowed to fall on a sensitized film in a
Debye- -Scherrer camera, will produce a pattern of arcs which are
symmetrical about the axis of the undeviated primary X—ray beam.
If the dimensions of the camera and the wave length of the X-rays
are known, it is possible to compute the spacings of the atomic
planes of the crystalline specimen from the distances of the' '
arcs from the primary beam. A knowledge of the interplanar
distances d will provide information, often not obtainable by
other methods, regarding the crystal structure and chemical
composition of the specimen, the identification of phases present,
and the determination of grain size, solid solubilities, and the
presence of internal and applied stresses.

For a simple diffraction pattern, the time required to cal-
culate interplanar distances fr_om measurements of the pattern is
not excessive. If more than a few lines are present, however,
or if several simple patterns are to be studied, it is very advan-
tageous to have available a table giving interplanar spacings
directly in terms of the linear measurements made on the film of
the lines appearing in the diffraction pattern. The preparation
of a table was undertaken at the NACA Cleveland laboratory wHEn' _
the expansion of research involving X-ray diffraction techniques a
indicated that such a table would greatly decrease the time
required to analyze_ diffraction patterns. The table was prepared
for use with Kh1.radiation from the following—target materials:

Molybdenum copper cobalt iron, and chromium . The d values
for cobalt-were obtained from reference l The sine values of the
angle .9 formed by incidence of the primary X—ray beam_.on an
atomic plane were obtained from reference 2 and range from O to
1.0000. -The d _values 'for molybdenum, copper, iron, and chrambun
were calculated by_ the Computing Section_gf_ the Engine Research
Division under the direction of Miss Margaret L. Strickland.