What is a Quadrupole? Antiferroquadrupolar Ordering State Explained

[mikeey]

hi, could anyone tell what a
quadrupole
quadrupolar ordering state
or an antiferroquadrupolar ordering state is?

i am a collage student, i have access to a collage library but can find very little.
it seems to be a very specialist subject and information is hard to come by.

i understand what antiferromagnetic ordering is, and i expect antiferroquadrupolar is the
same but with molecules that possesses 4 dipoles or something like that?
am i even close?

 

[olgranpappy]

"collage"--noun: a technique of composing a work of art by pasting on a single surface various materials not normally associated with one another, as newspaper clippings, parts of photographs, theater tickets, and fragments of an envelope.

Sorry, I couldn't resist. Anyways, A quadrupole is typically the third term in an expansion of the electric field (or other field) of an extended body. Usually we are interested in the quadrupole term when the first two terms (monopole and dipole) are zero. For example, consider a square with charges at the corners of the square. If the charges alternate in sign as we go around the square then the system has zero monopole and dipole moment, but a non-zero quadrupole momentum.

For more info you could try google.

 

[Gokul43201]

A better starting place than Google is any standard undergrad E&M text (e.g., Griffiths).