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Crystals are composed of the same stuff assembled in a periodic fashion.

I understand that there are possible and less possible bonds. Like complementary electric charge, ie. things must stick together or at least not repulse each other.

However I find it difficult to understand why this development process (crystal growth) is that selective and does not result in the assembly of more random bricks together.

I did not find Wikipedia crystal growth article to be helpful.

It seems to me there is a sort of recognition process at hand, and the same element is the optimal choice. My guess is it could be the winner over other bricks by creating the most adherence, while other species would adhere but less stably or not even adhere at all.

I also suppose there are impurities in crystals. I also know some artificial crystals can be fed with a very precise "soup", preventing impurities to insert in the crystal. But this question is not about small defects.

One can find ice or NaCl salt naturally occurring and they are indeed common crystals, so this mechanism does not seem to be highly dependent on the crystal growing in a very unique environment.

Lastly, I acknowledge there is a logical flaw in my question. If it was not the same stuff spatially repeating, it would not be called a crystal in the first place. This is post hoc naming. But hopefully there is more to it, including why crystals exist at all.

Winston
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  • Growing large, single crystals is actually quite hard unless they are highly valued ones (like silicon for semiconductor devices). Why impurities may or may not get incorporated is mostly a question of thermodynamics vs kinetics of solidification. Overall, this question is quite broad. – Jon Custer Sep 17 '20 at 16:13
  • This is not about impurities, and ironically I deleted this part of the question, I am going to put it back. – Winston Sep 17 '20 at 16:18
  • So are you asking why there are crystals at all? – Jon Custer Sep 17 '20 at 16:19
  • Yes but I am afraid that if I ask only why there are crystals at all, I will not get an explanation that covers the mechanism of selection. – Winston Sep 17 '20 at 16:24
  • Still, crystal growth is the sole topic of a number of textbooks and multiple journals. Can you refine this down to a more directly answered question? – Jon Custer Sep 17 '20 at 16:27
  • No because I want to know if there are general principles behind this selection, not an explanation limited to one crystal type. I doubt there is really zero commonality. – Winston Sep 17 '20 at 16:31
  • What is it you actually suggest? – Winston Sep 17 '20 at 16:33
  • Do you mean selectivity with respect to positions of the atoms (like "why periodic?"), or selectivity with respect to species of the atom, like where Na would be placed in NaCl vs where Cl would? Or something else? – Ruslan Sep 17 '20 at 19:25
  • With respect to species, as if it only accepts particular materials to join in. – Winston Sep 17 '20 at 19:48

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