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I was reading through a chapter named 'Solid state' in the NCERT Chemistry book.

I learnt about anisotropy of crystalline solids.

And what I understood was, you measure a certain property of that solid in one direction and it could be X while you measure it in the other direction it could be Y.

I then learnt about how a solid could show the property of birefringence.


My question : So does that mean, even electrical conductivity isn't the same in all directions? Does that mean a copper wire is going to conduct differently in different directions? How is that possible? It feels impossible? Does that mean different copper wires conduct differently?


I understand the last part is like a chunk of questions altogether and our community doesn't like that, but then it is basically having the same origin with just a little counter questions kinda? so I just let that be. I believe the contributors can understand what confusion I'm dealing with if I ask it like that.

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    $\begingroup$ Copper is a bad example: it has cubic structure, hence the tensor is spherical and conductivity the same in all directions. Better think of graphite. $\endgroup$ Mar 21, 2021 at 13:23
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    $\begingroup$ And as noted, single crystal graphite has different conductivities in plane vs out of plane. Hcp metals not so much. $\endgroup$
    – Jon Custer
    Mar 21, 2021 at 15:16
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    $\begingroup$ Note that deletion of questions with answers, where the responders have spent their effort on, is disrespect to users and may highly discourage from posting answers to the questions of the same author. Consider your actions. $\endgroup$
    – Poutnik
    Apr 2, 2021 at 12:18
  • $\begingroup$ @Poutnik Oh, I apologize for that. Didn't mean to disrespect. I thought my question was trivial. And you mentioned the same too? I once came across a chat from the moderators where they would delete the questions that seemed trivial/were AMiRite type? I shall keep your warning in mind. Don't worry :) I appreciate your effort though. No disrespect. $\endgroup$
    – Desai
    Apr 2, 2021 at 12:40
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    $\begingroup$ Ok, apology accepted. It is good to write such a comment about deletion decision, before deletion itself, so users can read it. ( It is not really deleted, just hidden from junior users). BTW,nobody is safe from occasionally asking trivial questions, not looking so at the asking moment. $\endgroup$
    – Poutnik
    Apr 2, 2021 at 12:45

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There are indeed compounds with very different conductivity in different directions

Depending on the structure of the crystal, it is possible that a compound has very different properties in different directions. Some crystal structures cannot show this as they are essentially the same in all spatial directions, but others can. Metals don't usually have anisotropic conductivity due to the nature of the conduction bands but other conductors can show it.

The archetypal compound that shows this property is graphite. Graphite consists of multiple flat layers of covalently bonded C-6 hexagons in an extended plane stacked on top of each other by much weaker forces. The delocalised electrons in the plane can conduct electricity well but there is little scope for electrons to move freely perpendicular to the plane. So the conductivity is about 1,000 times higher along the plane than it is perpendicular to it (see Electrical conductivity of graphite).

So it is certainly possible that electrical conductivity can be different in different crystal directions. But this requires particular structural features. Other forms of anisotropy are far more common (like birefringence).

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  • $\begingroup$ For organic materials (with a much greater likelihood to crystallize in lower symmetry space groups of the monoclinic and triclinic class, than inorganic materials [based on counting the entries in the CSD and ICSD database per space group]) I rather would support for them the perspective isotropy is a specialty when it comes to vector / tensor properties. On the other hand, e.g., in organic electronics (like solar cells, OLEDs), there are instances where crystallinity / a regular spatial arrangement of the molecules is a hindrance to the devices built and thus not wanted at all. $\endgroup$
    – Buttonwood
    Mar 22, 2021 at 13:33

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