Î'
l
ll
l
_
9—11.
LAUE spors AND CRYSTAL ANALYSIS 209
3/65 and 6/66. The Miller indices of
plane are then said to
,
beh=2,k=3andl=6.
,
_
perpendicular distance ;! between those Bragg planes '
Wh1Ch have the same Miller indices is given by
‘
'
'
΀2
22 *
a2
’
52
-
'
(
)
This reduces to
'
ï
’
'
…
d = a/’V Æ2 + k2 + 12
‘
(9—10)
for a crystal such as rock salt which has a cubiclattice; i.e.,
_
'
where a = & = 6.
If the last equation is substitüted in Bragg’s
law, and 7172 = H, 771€ = K and 71! : L,we arriVe at equation 3—12
used in the electron diffraction experiments.
,
'
For the case of X—rays incident along one of the three “major
axes
of a cubic crystal, it is comparatively easy to associateeach
,
,
Lane spot With its reection plane.
can be seen
…
from gure
9—13, that
_
,
‘
7_
'
,
tan 29 = r/K …
…
f»_
,
,,
…
Itcanalso be'shown that
'
Ï
,
_
;…-“
25…$
2 ‘j2
,
'
’
'
'* The polar» coordmatesrand -
measuredaswcas
aSdetermmedbÿtl‘1alandemrWh1ChnumeflcallYsaüSfÿeclua
.
tlns9—12and9—13,aœtheMlef1n1œS@fthePlane
z
*
Ü
»
thelrmterpretaüonmakesït°SSïbletoreducethenumbef@f -"
'
Ï…:
,
‘
—