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[oliverkeers13]

Not Porcupine

[tsh]

OK.... Only just started on this lark, so I'm not up to speed with how hard these silver cards are, but the clue seems to just re-inforce the idea that the card is a diffraction pattern.
In a hall of mirrors, you see multiple images of yourself which are generated from a small number of mirrors. This is the opposite effect to the diffraction pattern where atoms at regular repeating locations (the images) cause constructive interference from the light source (you) and generate spits of light (the mittors).

My recolection of 2nd year physics is blurred, but I'm sure some patterns can be worked out by hand.

In order to reverse the pattern, some sort of fourier transform is required. My initial thoughts are that there is some sort of innacuacy in the printed pattern, and that there may be some levels of indirection in this puzzle!

[space cadet]

I've been playing around with connecting the dots, probably not done it right, but it makes it a bit easier to see what's going on and it might set off some bells with someone.

[oliverkeers13]

hmm...that looks a bit like a hydrocarbon polymer. these only have 4 bonds, however, so it doesn't quite look right. Have you joined them up in any order? like ascending values.

[tsh]

I think you've mis-understood the picture. It is not a diagram of a molecule.

As an example, look at a point light source (like a street lamp) through a fine cloth. The regular square array of holes in the cloth should form a cross pattern, the shape of the holes affects the fine structure of the pattern.

I think I might have an answer though, just need to get a card now! I think it's simpler than people think!

Sean

[space cadet]

I didn't join them up particularly because I think it's molecule, but to try and define a shape or see how it mirrors. Here's another drawing... I don't think it's obvious how (if) they should be connected, but the grid should explain the coordinates.



Let us know what you think tsh and we can always try it!

[GasparLewis]

If you could make that diagram again without the line drawing, I think it would make everybody very, very happy.

That's just about exactly what we needed: a large-type information reprint. Order to chaos, order to chaos.

And keep trying to ask actual crystallographer.

Pity this wasn't a guest puzzle; might have gone down like "Polar" if Kurt wasn't the party responsible.

[space cadet]

Here you go

[oliverkeers13]

Well the mirrors thing is obvious then. The numbers on a standard (x,y) graph start in the negatives, pass 0, then go to positives, this goes the other way. A mirror would reverse the (incorrectly displayed) X co-ordinates, whilst keeping the (correct) y co-ordinates in the same place.

[ALISDAIRPARK]

I'm not sure the lines are correct, the coordinates run as xyz, with all the y's as 0, so where the drawing appears 3D I think this is only one layer?

For the grid, the horizontal lines should actually slant slightly, for example the three -4 z coordinates in the centre.

With no crystallography expertise whatsoever I would still say there seems to be a hexagonal element. I've also e-mailed a couple of experts, but it's into the festive season so I doubt they will pick up the mail until next semester...

[space cadet]

I'm not sure the lines are correct neither, but it does seem like the coordinates are x and y, and that z has to be worked out from the size of the dots. You're right about the grid though so here's another one!! Both horizontal and vertical lines are slanted. Which makes the middle bit not look like a hex, but a 3D cube shape perhaps...

[Uhtoff]

As for crystal structure I've read a fair few things that suggest (although possibly incorrectly) that the structure symmetry can be determined from the symmetry of the diffraction pattern. As this pattern has no mirror/line symmetry and has only 2nd order rotational symmetry it suggests it's a sphenoidal monoclinic crystal. Not sure exactly where that gets us

[tsh]

It probably helps to draw lines in a 3rd plane as well, from 2,-4 to -2,4 etc. As someone noted earlier, the coordinates might map back into the crystal structure (sorry, none of my text books explain this)

It seems odd that this patern only has rotational symmetry - everything else I've seen has several lines of mirror symmetry...

Another idea is to see if the pattern can be reduced into a simpler pattern which is superimposed several times (with the appropriate intensities).

Sean

[ALISDAIRPARK]

that grid's spot on Spacecadet!

[spolier] I just tried Graphite based on the hex thing, and noone had listed a try...no joy[/spolier]

If you look at the spiral it looks kind of like a spiral galaxy, however I don't think there would be stars in straight lines.

[tsh]

OK, I think this is what the numbers map to in terms of planes of atoms in the crystal. Not sure it adds much - it still looks easier guessing names than trying to work backwards to come up with an answer.
If I've understood, there can be atoms anywhere the planes intersect, and there must be enough to define all the planes. No guarantees that I've not mis-transcribed the numbers though!