Atomic Structure: "Long Range" and "Short Range" Translation

[tony_engin]

Hi everyone
I missed some content in my lecture about atomic structure of atoms.
In the lecture, the lecturer talked something about "slipping" , "easy directions" and "slip systems"...I don't really catch these stuff in this lecture. But I could find these in textbook. What makes me most confusing is "long range" and "short range" translation. I just recall that they are something about how an atom slip over a closest packed plane, and the lecturer throw out some "short range" and "long range" and finally said that it is some "zig-zag" movement for face-centered-cubic indeed...
something like this...Is there anyone know what is the content? Can you explain to me?
Really many thanks!

 

[Gokul43201]

I'm not sure I recall anything about "long range/short range traslations". Are you perhaps speaking of Burger's vectors ?

This thread belongs in Materials Science.

 

[Astronuc]

Slipping has to do with the motion of planes of atoms with respect to one another. This invovles the motion of dislocations (defects) in the lattice.

There are point defects and line defects.

Dislocations can 'glide' and 'climb'. The gliding is in the direction of the planes of atoms. A dislocation may climb (move perpendicular to the initial atomic plane) over an obstacle, such as an interstial atom, and then proceed on a path parallel to the original path.

Zig-zagging probably refers to a combination of 'glide' and 'climb'.

 

[PerennialII]

Your short / long range might have to do with stacking fault energies and the resulting characteristics of dislocation movement in different kind of lattices ? For example when you compare partial dislocation behavior in typical fcc and bcc metals.