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(materials science) slip system

by asdf1
Tags: materials, science, slip
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asdf1
#1
Sep1-06, 01:00 AM
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for the FCC cubic, there are 12 slip systems: 4 {111} planes and 3 <110> directions...
what i don't understand is why are there 4{111} planes instead of 1?
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Astronuc
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Sep2-06, 07:11 PM
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How many corners to a cube? How many major diagonals?
Gokul43201
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Sep3-06, 06:03 PM
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Quote Quote by asdf1
what i don't understand is why are there 4{111} planes instead of 1?
In a cube, you'll find you can draw 8 {1,1,1} planes. However, you'll also see that only 4 of these are unique - the other 4 being parallel to these and separated from them by distance of a/sqrt(3), where 'a' is the cube edge.

What I don't understand is why there are only 3 <110> directions when it looks to me like there should be 6 (2 face diagonals on each of the 3 faces).

Astronuc
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Sep4-06, 07:35 AM
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(materials science) slip system

Rotational symmetry - rotate the cube 90° about the normal to the face plane, and one face diagonal transforms to the other (perpendicular) diagonal.

Or rotate the cube 180° about the normal to the base and the <110> becomes <1[itex]\bar1[/itex]0>.
asdf1
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Sep5-06, 05:23 AM
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ok~ thank you!
Gokul43201
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Sep6-06, 04:03 PM
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Quote Quote by Astronuc
Rotational symmetry - rotate the cube 90 about the normal to the face plane, and one face diagonal transforms to the other (perpendicular) diagonal.

Or rotate the cube 180 about the normal to the base and the <110> becomes <1[itex]\bar1[/itex]0>.
Doesn't this argue that there is only one relevant <110> direction? After all, I can generate the other 5 face diagonals from any one, using a combination of symmetry preserving rotations.

Yikes! I've completely lost touch with basic crystallography - time to hit the books.


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