I Why are the crystallographic direction indices u,v, and w?

Stenny
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Why are the crystallographic direction indices u,v, and w? And as an add on, why are the miller indices h,k, and l? Why did we pick these letters for each? I’m having a tough time remembering which letters to use and some context might help.
 
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This would go into the history of science forum if we had one. Let me see what I can look up about this.
 
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There's no secret or specific meaning behind 'h,k,l'. They were adopted by Miller in his 1839 treatise on crystallography from an article by Whewell from 1825.

As for 'u,v,w' there's also no relevant meaning to them, they are the closest to 'x,y,z'. Before QM, crystallography was foremost geometry, so one had to use a huge apparatus of letters to distinguish things.
 
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From the BCS theory of superconductivity is well known that the superfluid density smoothly decreases with increasing temperature. Annihilated superfluid carriers become normal and lose their momenta on lattice atoms. So if we induce a persistent supercurrent in a ring below Tc and after that slowly increase the temperature, we must observe a decrease in the actual supercurrent, because the density of electron pairs and total supercurrent momentum decrease. However, this supercurrent...
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