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In mineralogy and crystallography, a crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid.

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Are there any crystal structures of the free base? The structure of the hydrochloride was published by D. W. Robertson and co-workers in J. Med. Chem., 1988, 31, 185–189 (DOI). The structure of 1:1 …
answered Oct 25 '14 by Klaus-Dieter Warzecha
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In Crystal structure of Sm5Ge4, the structure is described as orthorhombic with $a = 7.75\,\mathring{A}$, $b = 14.94\,\mathring{A}$ and $c = 7.84\,\mathring{A}$, having four $\ce{Sm5Ge4}$ units per u …
answered Mar 26 '14 by Klaus-Dieter Warzecha
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The cubic primitive, cubic body-centered and the cubic face-centered are just the three possible Bravais lattices of the cubic crystal system. In total, we know seven crystal systems, namely (in orde …
answered Feb 21 '14 by Klaus-Dieter Warzecha
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Does the 1958 Nature paper by Kendrew include any useful details? (Sorry, I'm behind a paywall right now).
answered Jan 14 '14 by Klaus-Dieter Warzecha
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Taking into account that gems often are doped oxides with rather high melting points, your project is quite a challenge. A historical example for synthetic emerald is Igmerald, produced by the I.G. F …
answered Mar 28 '14 by Klaus-Dieter Warzecha
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As pointed out by Geoff Hutchinson, this isn't currently possible by Avogadro and OpenBabel - and he should know best ;) Since you want to visualize a feature of crystalline systems, you might want t …
answered Sep 12 '14 by Klaus-Dieter Warzecha
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To my knowledge, pure(!) calcium sulfate does not show thermoluminescence. It is however true that it can be turned into thermoluminescent materials by doping with rare metals, such as dysprosium or …
answered Mar 8 '17 by Klaus-Dieter Warzecha
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In my own work, I've never used the term polymorph for anything but molecular crystals in a highly but differently ordered solid state. In the case of crystal solids, it seems clear that allotropy …
answered Apr 5 '15 by Klaus-Dieter Warzecha
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In the crystal, carboxylic acids mostly form dimers through pairs of $\ce{OH\bond{~}O=C}$ hydrogen bonds. In some cases, infinite chains of hydrogen bonds are formed instead: here, each carboxylic ac …
answered Apr 17 '15 by Klaus-Dieter Warzecha
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The thermochromism of $\ce{ZnO}$ results from a minor loss of oxygen upon heating to temperatures around 800 °C, i.e. a non-stoichiometric $\ce{Zn$_{1+x}$O}$ with $x = 7 \times 10^{-5}$ is formed. U …
answered Jan 9 '14 by Klaus-Dieter Warzecha
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The box in my kitchen is labelled "reine Zitronensäure" (= pure citric acid) and "lebensmittelsauber". According to the manufacturer, the latter means that citric acid in this quality can be used to …
answered Sep 16 '14 by Klaus-Dieter Warzecha
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The coordinates of the hydrogen atoms of the methyl group in question are there (H16a, H16b, H16c). The problem is a rendering problem of the Accelrys visualizer. Other tools don't have a problem w …
answered Apr 30 '15 by Klaus-Dieter Warzecha
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The absorption of a photon en route to an electronically excited Franck-Condon state typically typically proceeds in the femtosecond range. The lifetime of an electronically excited singlet state mos …
answered Sep 7 '14 by Klaus-Dieter Warzecha