Editing X-ray crystallography (section)

==History==
{{Multiple image|total_width=300
|image1=Kepler conjecture 1.jpg
|alt1=
|caption1=Drawing of square (A) and hexagonal (B) packing from [[Johannes Kepler|Kepler's]] work, ''Strena seu de Nive Sexangula''.
|image2=Snowflake8.png
|alt2=
|caption2=The hexagonal symmetry of snowflakes results from the [[tetrahedron|tetrahedral]] arrangement of [[hydrogen bond]]s about each water molecule.
}}
Crystals, though long admired for their regularity and [[symmetry]], were not investigated scientifically until the 17th century. [[Johannes Kepler]] hypothesized in his work ''Strena seu de Nive Sexangula'' (A New Year's Gift of Hexagonal Snow) (1611) that the hexagonal symmetry of [[Snowflake|snowflake crystals]] was due to a regular packing of spherical water particles.<ref>{{cite book|vauthors= Kepler J|author-link= Johannes Kepler|date= 1611|title= Strena seu de Nive Sexangula|publisher= G. Tampach|location= Frankfurt|url= http://www.thelatinlibrary.com/kepler/strena.html|isbn= 3-321-00021-0|access-date= 2008-08-25|archive-date= 2011-09-19|archive-url= https://web.archive.org/web/20110919163249/http://www.thelatinlibrary.com/kepler/strena.html|url-status= live}}</ref> The Danish scientist [[Nicolas Steno]] (1669) pioneered experimental investigations of crystal symmetry. Steno showed that the angles between the faces are the same in every exemplar of a particular type of crystal ([[law of constancy of interfacial angles]]).<ref>{{cite book| vauthors = Steno N |author-link= Nicolas Steno|date= 1669|title= De solido intra solidum naturaliter contento dissertationis prodromus|publisher= Florentiae}}</ref> [[René Just Haüy]] (1784) discovered that every face of a crystal can be described by simple stacking patterns of blocks of the same shape and size ([[Law of rational indices|law of decrements]]). Hence, [[William Hallowes Miller]] in 1839 was able to give each face a unique label of three small integers, the [[Miller index|Miller indices]] which remain in use for identifying crystal faces. Haüy's study led to the idea that crystals are a regular three-dimensional array (a [[Bravais lattice]]) of atoms and [[molecule]]s; a single [[unit cell]] is repeated indefinitely along three principal directions. In the 19th century, a complete catalog of the possible symmetries of a crystal was worked out by [[Johann F. C. Hessel|Johan Hessel]],<ref>{{cite book| vauthors = Hessel JF |date= 1831|title= Kristallometrie oder Kristallonomie und Kristallographie|publisher= Leipzig}}</ref> [[Auguste Bravais]],<ref>{{cite journal| vauthors = Bravais A|author-link= Auguste Bravais|date= 1850|title= Mémoire sur les systèmes formés par des points distribués regulièrement sur un plan ou dans l'espace|journal= Journal de l'École Polytechnique|volume= 19|page=1}}</ref> [[Evgraf Fedorov]],<ref>{{Cite journal|vauthors= Shafranovskii II, Belov NV|title= E. S. Fedorov|journal= 50 Years of X-Ray Diffraction|editor= Paul Ewald|publisher= Springer|date= 1962|isbn= 90-277-9029-9|url= http://www.iucr.org/iucr-top/publ/50YearsOfXrayDiffraction/fedorov.pdf|page= 351|access-date= 2007-09-25|archive-date= 2007-09-28|archive-url= https://web.archive.org/web/20070928070656/http://www.iucr.org/iucr-top/publ/50YearsOfXrayDiffraction/fedorov.pdf|url-status= live}}</ref> [[Arthur Moritz Schönflies|Arthur Schönflies]]<ref>{{cite book| vauthors = Schönflies A|author-link= Arthur Moritz Schönflies|date= 1891|title= Kristallsysteme und Kristallstruktur|publisher= Leipzig}}</ref> and (belatedly) [[William Barlow (geologist)|William Barlow]] (1894). Barlow proposed several crystal structures in the 1880s that were validated later by X-ray crystallography;<ref>{{cite journal|vauthors= Barlow W|date= 1883|title= Probable nature of the internal symmetry of crystals|journal= Nature|volume= 29|page= 186|doi= 10.1038/029186a0|issue= 738|bibcode= 1883Natur..29..186B|url= https://zenodo.org/record/1429283|doi-access= free|access-date= 2019-09-10|archive-date= 2020-03-29|archive-url= https://web.archive.org/web/20200329132634/https://zenodo.org/record/1429283|url-status= live}} See also {{cite journal| vauthors =  Barlow W |title= Probable Nature of the Internal Symmetry of Crystals|journal= Nature|volume= 29|page=205|date= 1883|doi= 10.1038/029205a0|issue= 739|bibcode = 1883Natur..29..205B |doi-access= free}} {{cite journal|vauthors= Sohncke L|title= Probable Nature of the Internal Symmetry of Crystals|journal= Nature|volume= 29|page= 383|date= 1884|doi= 10.1038/029383a0|issue= 747|bibcode= 1884Natur..29..383S|s2cid= 4072817|url= https://zenodo.org/record/1429283|access-date= 2019-09-10|archive-date= 2020-03-29|archive-url= https://web.archive.org/web/20200329132634/https://zenodo.org/record/1429283|url-status= live}} {{cite journal|vauthors= Barlow WM|title= Probable Nature of the Internal Symmetry of Crystals|journal= Nature|volume= 29|page= 404|date= 1884|doi= 10.1038/029404b0|issue= 748|bibcode= 1884Natur..29..404B|s2cid= 4016086|url= https://zenodo.org/record/1429283|doi-access= free|access-date= 2019-09-10|archive-date= 2020-03-29|archive-url= https://web.archive.org/web/20200329132634/https://zenodo.org/record/1429283|url-status= live}}</ref> however, the available data were too scarce in the 1880s to accept his models as conclusive.

[[File:3D model hydrogen bonds in water.svg|thumb|Model of the arrangement of water molecules in ice, revealing the [[hydrogen bond]]s (1) that hold the solid together.]]

[[Wilhelm Röntgen]] discovered X-rays in 1895.<ref name="Stoddart">{{cite journal |vauthors=Stoddart C |title=Structural biology: How proteins got their close-up |journal=Knowable Magazine |date=1 March 2022 |doi=10.1146/knowable-022822-1 |doi-access=free |url=https://knowablemagazine.org/article/living-world/2022/structural-biology-how-proteins-got-their-closeup |access-date=25 March 2022 |archive-date=7 April 2022 |archive-url=https://web.archive.org/web/20220407231646/https://knowablemagazine.org/article/living-world/2022/structural-biology-how-proteins-got-their-closeup |url-status=live }}</ref> Physicists were uncertain of the nature of X-rays, but suspected that they were waves of [[electromagnetic radiation]]. The [[James Clerk Maxwell|Maxwell]] theory of [[electromagnetic radiation]] was well accepted, and experiments by [[Charles Glover Barkla]] showed that X-rays exhibited phenomena associated with electromagnetic waves, including transverse [[Polarization (waves)|polarization]] and [[spectral line]]s akin to those observed in the visible wavelengths. Barkla created the x-ray notation for sharp spectral lines, noting in 1909 two separate energies, at first naming them "A" and "B" and then supposing that there may be lines prior to "A", he started an alphabet numbering beginning with "K."<ref>Barkla, Charles G. (1911). "XXXIX.The spectra of the fluorescent Röntgen radiations". Philosophical Magazine. Series 6. 22 (129): 396–412. doi:10.1080/14786440908637137.</ref><ref name="Michael Eckert 2011">Michael Eckert, Disputed discovery: the beginnings of X-ray diffraction in crystals in 1912 and its repercussions, January 2011, Acta crystallographica. Section A, Foundations of crystallography 68(1):30–39 This Laue centennial article has also been published in Zeitschrift für Kristallographie [Eckert (2012). Z. Kristallogr. 227, 27–35].</ref> Single-slit experiments in the laboratory of [[Arnold Sommerfeld]] suggested that X-rays had a [[wavelength]] of about 1 [[angstrom]].<ref>Nisio, Sigeko. "The Formation of the Sommerfeld Quantum Theory of 1916." (1974) JSHS, No.12. pp39-78.</ref> X-rays are not only waves but also have particle properties causing Sommerfeld to coin the name [[Bremsstrahlung]] for the continuous spectra when they were formed when electrons bombarded a material.<ref name="Michael Eckert 2011" /> [[Albert Einstein]] introduced the photon concept in 1905,<ref>{{cite journal| vauthors = Einstein A|author-link= Albert Einstein|date= 1905|title= Über einen die Erzeugung und Verwandlung des Lichtes betreffenden heuristischen Gesichtspunkt |trans-title= A Heuristic Model of the Creation and Transformation of Light|journal= [[Annalen der Physik]]|volume= 17|page=132|bibcode= 1905AnP...322..132E |doi= 10.1002/andp.19053220607|issue= 6 |language= de|doi-access= free}}. An [[s:A Heuristic Model of the Creation and Transformation of Light|English translation]] is available from [[Wikisource]].</ref> but it was not broadly accepted until 1922,<ref>Compare: {{cite journal| vauthors = Einstein A|date= 1909|title= Über die Entwicklung unserer Anschauungen über das Wesen und die Konstitution der Strahlung |trans-title= The Development of Our Views on the Composition and Essence of Radiation |journal= Physikalische Zeitschrift|volume= 10|page=817|language= de}}. An [[s:The Development of Our Views on the Composition and Essence of Radiation|English translation]] is available from [[Wikisource]].</ref><ref>{{cite book| vauthors = Pais A |author-link= Abraham Pais|date= 1982|title= Subtle is the Lord: The Science and the Life of Albert Einstein|publisher= [[Oxford University Press]]|isbn= 0-19-853907-X|url= https://archive.org/details/subtleislordscie00pais}}</ref> when [[Arthur Compton]] confirmed it by the scattering of X-rays from electrons.<ref>{{cite journal|vauthors= Compton A|author-link= Arthur Compton|date= 1923|title= A Quantum Theory of the Scattering of X-rays by Light Elements|journal= Phys. Rev.|volume= 21|page= 483|doi= 10.1103/PhysRev.21.483|url= https://history.aip.org/history/exhibits/gap/PDF/compton.pdf|issue= 5|bibcode= 1923PhRv...21..483C|doi-access= free|access-date= 2019-09-15|archive-date= 2020-08-10|archive-url= https://web.archive.org/web/20200810055602/https://history.aip.org/history/exhibits/gap/PDF/compton.pdf|url-status= live}}</ref> The particle-like properties of X-rays, such as their ionization of gases, had prompted [[William Henry Bragg]] to argue in 1907 that X-rays were ''not'' electromagnetic radiation.<ref>{{cite journal| vauthors = Bragg WH|author-link= William Henry Bragg|date= 1907|title= The nature of Röntgen rays|journal= Transactions of the Royal Society of Science of Australia|volume= 31|page=94}}</ref><ref>{{cite journal|vauthors= Bragg WH|date= 1908|title= The nature of γ- and X-rays|journal= Nature|volume= 77|page= 270|doi= 10.1038/077270a0|issue= 1995|bibcode= 1908Natur..77..270B|s2cid= 4020075|url= https://zenodo.org/record/1429495|access-date= 2019-09-10|archive-date= 2020-03-29|archive-url= https://web.archive.org/web/20200329132644/https://zenodo.org/record/1429495|url-status= live}} See also {{cite journal|vauthors= Bragg WH|title= The Nature of the γ and X-Rays|journal= Nature|volume= 78|page= 271|date= 1908|doi= 10.1038/078271a0|issue= 2021|bibcode= 1908Natur..78..271B|s2cid= 4039315|url= https://zenodo.org/record/1429507|doi-access= free|access-date= 2020-06-03|archive-date= 2021-03-27|archive-url= https://web.archive.org/web/20210327105811/https://zenodo.org/record/1429507|url-status= live}} {{cite journal| vauthors = Bragg WH |title= The Nature of the γ and X-Rays|journal= Nature|volume= 78|page=293|date= 1908|doi= 10.1038/078293d0|issue= 2022|bibcode= 1908Natur..78..293B |s2cid= 3993814}} {{cite journal|vauthors= Bragg WH|title= The Nature of X-Rays|journal= Nature|volume= 78|page= 665|date= 1908|doi= 10.1038/078665b0|issue= 2035|bibcode= 1908Natur..78R.665B|s2cid= 4024851|url= https://zenodo.org/record/1429511|doi-access= free|access-date= 2020-08-27|archive-date= 2021-03-27|archive-url= https://web.archive.org/web/20210327105819/https://zenodo.org/record/1429511|url-status= live}}</ref><ref>{{cite journal|vauthors= Bragg WH|date= 1910|title= The consequences of the corpuscular hypothesis of the γ- and X-rays, and the range of β-rays|journal= Phil. Mag.|volume= 20|page= 385|doi= 10.1080/14786441008636917|issue= 117|url= https://zenodo.org/record/1430874|access-date= 2019-09-10|archive-date= 2020-03-29|archive-url= https://web.archive.org/web/20200329132633/https://zenodo.org/record/1430874|url-status= live}}</ref><ref>{{cite journal| vauthors = Bragg WH |date= 1912|title= On the direct or indirect nature of the ionization by X-rays|doi= 10.1080/14786440408637253 |journal= Phil. Mag.|volume= 23|page=647|issue= 136}}</ref>  Bragg's view proved unpopular and the observation of [[X-ray diffraction]] by [[Max von Laue]] in 1912<ref name="L1912">{{cite journal |vauthors=Friedrich W, Knipping P, von Laue M |date=1912 |title=Interferenz-Erscheinungen bei Röntgenstrahlen |url=https://commons.wikimedia.org/wiki/File%3AInterferenz-Erscheinungen_bei_R%C3%B6ntgenstrahlen.pdf |journal=Sitzungsberichte der Mathematisch-Physikalischen Classe der Königlich-Bayerischen Akademie der Wissenschaften zu München |volume=1912 |page=303 |trans-work=Interference phenomena in X-rays |access-date=2024-07-14 |archive-date=2024-05-21 |archive-url=https://web.archive.org/web/20240521103746/https://commons.wikimedia.org/wiki/File:Interferenz-Erscheinungen_bei_R%C3%B6ntgenstrahlen.pdf |url-status=live }}</ref> confirmed that X-rays are a form of electromagnetic radiation. [[File:Interferenz-Erscheinungen bei Röntgenstrahlen Tafel II Fig. 5.jpg|thumb|One of the copper sulfate X-ray interference patterns published in Von Laue's 1912 paper{{r|L1912}}.]]

The idea that crystals could be used as a [[diffraction grating]] for [[X-ray]]s arose in 1912 in a conversation between [[Paul Peter Ewald]] and [[Max von Laue]] in the [[Englischer Garten|English Garden]] in Munich. Ewald had proposed a resonator model of crystals for his thesis, but this model could not be validated using [[visible light]], since the wavelength was much larger than the spacing between the resonators. Von Laue realized that electromagnetic radiation of a shorter wavelength was needed, and suggested that X-rays might have a wavelength comparable to the unit-cell spacing in crystals. Von Laue worked with two technicians, [[Walter Friedrich]] and his assistant Paul Knipping, to shine a beam of X-rays through a [[Copper(II) sulfate|copper sulfate]] crystal and record its diffraction on a [[photographic plate]]. After being developed, the plate showed a large number of well-defined spots arranged in a pattern of intersecting circles around the spot produced by the central beam. The results were presented to the [[Bavarian Academy of Sciences and Humanities]] in June 1912 as "Interferenz-Erscheinungen bei Röntgenstrahlen" (Interference phenomena in X-rays).<ref name="L1912"/><ref>{{cite journal |vauthors=von Laue M |date=1914 |title=Concerning the detection of x-ray interferences |url=http://nobelprize.org/nobel_prizes/physics/laureates/1914/laue-lecture.pdf |journal=Nobel Lectures, Physics |volume=1901–1921 |access-date=2009-02-18 |archive-date=2010-12-07 |archive-url=https://web.archive.org/web/20101207113911/http://nobelprize.org/nobel_prizes/physics/laureates/1914/laue-lecture.pdf |url-status=live }}</ref> Von Laue developed a law that connects the scattering angles and the size and orientation of the unit-cell spacings in the crystal, for which he was awarded the [[Nobel Prize in Physics]] in 1914.<ref>{{cite book |title=A Textbook of Mineralogy |vauthors=Dana ES, Ford WE |date=1932 |publisher=John Wiley & Sons |edition=fourth |location=New York |page=28}}</ref>

[[File:Diamond and graphite2.jpg|thumb|Although diamonds (top left) and [[graphite]] (top right) are identical in chemical composition—being both pure [[carbon]]—X-ray crystallography revealed the arrangement of their atoms (bottom). In diamond, the carbon atoms are arranged [[diamond cubic|tetrahedrally]] and held together by single [[covalent bond]]s. By contrast, graphite is composed of stacked sheets. Within the sheet, the bonding is covalent and has hexagonal symmetry, but there are no covalent bonds between the sheets.]]
After Von Laue's pioneering research, the field developed rapidly, most notably by physicists [[William Lawrence Bragg]] and his father [[William Henry Bragg]]. In 1912–1913, the younger Bragg developed [[Bragg's law]], which connects the scattering with evenly spaced planes within a crystal.<ref name="Stoddart"/><ref>{{cite journal|vauthors=Bragg WL|date=1912|title=The Specular Reflexion of X-rays|journal=Nature|volume=90|page=410|doi=10.1038/090410b0|issue=2250|bibcode=1912Natur..90..410B|s2cid=3952319|url=https://zenodo.org/record/1429558|doi-access=free|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132707/https://zenodo.org/record/1429558|url-status=live}}</ref><ref>{{cite journal| vauthors = Bragg WL|date = 1913|title=The Diffraction of Short Electromagnetic Waves by a Crystal|journal=Proceedings of the Cambridge Philosophical Society|volume=17|page=43}}</ref><ref>{{cite journal| vauthors = Bragg WL |date = 1914|title=Die Reflexion der Röntgenstrahlen|journal=Jahrbuch der Radioaktivität und Elektronik|volume=11|page=350}}</ref> The Braggs, father and son, shared the 1915 Nobel Prize in Physics for their work in crystallography. The earliest structures were generally simple; as computational and experimental methods improved over the next decades, it became feasible to deduce reliable atomic positions for more complicated arrangements of atoms.

The earliest structures were simple inorganic crystals and minerals, but even these revealed fundamental laws of physics and chemistry. The first atomic-resolution structure to be "solved" (i.e., determined) in 1914 was that of [[sodium chloride|table salt]].<ref>{{cite journal| vauthors = Bragg WL |date=1913|title=The Structure of Some Crystals as Indicated by their Diffraction of X-rays|journal=Proc. R. Soc. Lond.|volume=A89|issue=610|jstor=93488|pages=248–277|bibcode=1913RSPSA..89..248B|doi=10.1098/rspa.1913.0083|doi-access=free}}</ref><ref>{{cite journal|vauthors=Bragg WL, James RW, Bosanquet CH|date=1921|title=The Intensity of Reflexion of X-rays by Rock-Salt|journal=Phil. Mag.|volume=41|page=309|doi=10.1080/14786442108636225|issue=243|url=https://zenodo.org/record/1430965|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132638/https://zenodo.org/record/1430965|url-status=live}}</ref><ref>{{cite journal|vauthors=Bragg WL, James RW, Bosanquet CH|date=1921|title=The Intensity of Reflexion of X-rays by Rock-Salt. Part II|journal=Phil. Mag.|volume=42|page=1|doi=10.1080/14786442108633730|issue=247|url=https://zenodo.org/record/1430951|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132627/https://zenodo.org/record/1430951|url-status=live}}</ref> The distribution of electrons in the table-salt structure showed that crystals are not necessarily composed of [[covalent bond|covalently bonded]] molecules, and proved the existence of [[ionic compound]]s.<ref>{{cite journal|vauthors=Bragg WL, James RW, Bosanquet CH|date=1922|title=The Distribution of Electrons around the Nucleus in the Sodium and Chlorine Atoms|journal=Phil. Mag.|volume=44|page=433|doi=10.1080/14786440908565188|issue=261|url=https://zenodo.org/record/1430852|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132623/https://zenodo.org/record/1430852|url-status=live}}</ref> The structure of diamond was solved in the same year,<ref name=dia >{{cite journal|vauthors=Bragg WH, Bragg WL|date=1913|title=The structure of the diamond|journal=Nature|volume=91|page=557|doi=10.1038/091557a0|issue=2283|bibcode=1913Natur..91..557B|s2cid=3987932|url=https://zenodo.org/record/1429564|doi-access=free|access-date=2020-08-27|archive-date=2021-03-26|archive-url=https://web.archive.org/web/20210326103553/https://zenodo.org/record/1429564|url-status=live}}</ref><ref>{{cite journal| vauthors = Bragg WH, Bragg WL |date=1913|title=The structure of the diamond|journal= Proc. R. Soc. Lond.|volume=A89|page=277|doi=10.1098/rspa.1913.0084|issue=610|bibcode = 1913RSPSA..89..277B |doi-access=free}}</ref> proving the tetrahedral arrangement of its chemical bonds and showing that the length of C–C single bond was about 1.52 angstroms. Other early structures included copper,<ref>{{cite journal|vauthors=Bragg WL|date=1914|title=The Crystalline Structure of Copper|doi=10.1080/14786440908635219|journal=Phil. Mag.|volume=28|page=355|issue=165|url=https://zenodo.org/record/1430856|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132712/https://zenodo.org/record/1430856|url-status=live}}</ref> [[calcium fluoride]] (CaF<sub>2</sub>, also known as ''fluorite''), [[calcite]] (CaCO<sub>3</sub>) and [[pyrite]] (FeS<sub>2</sub>)<ref name=carb >{{cite journal| vauthors = Bragg WL|date = 1914|title=The analysis of crystals by the X-ray spectrometer|doi=10.1098/rspa.1914.0015 |journal=Proc. R. Soc. Lond.|volume=A89|page=468|issue=613|bibcode=1914RSPSA..89..468B |doi-access=free}}</ref> in 1914; [[spinel]] (MgAl<sub>2</sub>O<sub>4</sub>) in 1915;<ref>{{cite journal|vauthors=Bragg WH|author-link=William Henry Bragg|date=1915|title=The structure of the spinel group of crystals|doi=10.1080/14786440808635400|journal=Phil. Mag.|volume=30|page=305|issue=176|url=https://zenodo.org/record/1430832|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132637/https://zenodo.org/record/1430832|url-status=live}}</ref><ref>{{cite journal| vauthors = Nishikawa S |date=1915 |title=Structure of some crystals of spinel group|journal=Proc. Tokyo Math. Phys. Soc.|volume=8|page=199}}</ref> the [[rutile]] and [[anatase]] forms of [[titanium dioxide]] (TiO<sub>2</sub>) in 1916;<ref>{{cite journal|vauthors=Vegard L|date=1916|title=Results of Crystal Analysis|doi=10.1080/14786441608635544|journal=Phil. Mag.|volume=32|page=65|issue=187|url=https://zenodo.org/record/1430936|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132659/https://zenodo.org/record/1430936|url-status=live}}</ref> [[Manganese(II) hydroxide|pyrochroite]] (Mn(OH)<sub>2</sub>) and, by extension, [[brucite]] (Mg(OH)<sub>2</sub>) in 1919.<ref>{{cite journal|vauthors=Aminoff G|date=1919|title=Crystal Structure of Pyrochroite|journal=Stockholm Geol. Fören. Förh.|volume=41|page=407|doi=10.1080/11035891909447000|url=https://zenodo.org/record/1532436|access-date=2019-09-10|archive-date=2020-03-29|archive-url=https://web.archive.org/web/20200329132707/https://zenodo.org/record/1532436|url-status=live}}</ref><ref>{{cite journal | vauthors = Aminoff G|date = 1921|title=Über die Struktur des Magnesiumhydroxids|journal=Z. Kristallogr.|volume=56|page=505}}</ref> Also in 1919, [[sodium nitrate]] (NaNO<sub>3</sub>) and caesium dichloroiodide (CsICl<sub>2</sub>) were determined by [[Ralph Walter Graystone Wyckoff]], and the [[wurtzite]] (hexagonal ZnS) structure was determined in 1920.<ref>{{cite journal|vauthors=Bragg WL|date=1920|title=The crystalline structure of zinc oxide|doi=10.1080/14786440608636079|journal=Phil. Mag.|volume=39|page=647|issue=234|url=https://zenodo.org/record/1430802|access-date=2020-06-03|archive-date=2021-10-25|archive-url=https://web.archive.org/web/20211025083928/https://zenodo.org/record/1430802|url-status=live}}</ref>

The structure of [[graphite]] was solved in 1916<ref>{{cite journal|date = 1916|title=Interferenz an regellos orientierten Teilchen im Röntgenlicht I|journal=Physikalische Zeitschrift|volume=17|page=277| vauthors = Debije P, Scherrer P |author-link1=Peter Debye}}</ref> by the related method of [[powder diffraction]],<ref>{{cite journal| vauthors = Friedrich W|date = 1913|title=Eine neue Interferenzerscheinung bei Röntgenstrahlen|journal=Physikalische Zeitschrift|volume=14|page=317}}</ref> which was developed by [[Peter Debye]] and [[Paul Scherrer]] and, independently, by [[Albert Hull]] in 1917.<ref>{{cite journal| vauthors = Hull AW|author-link=Albert Hull|date = 1917|title=A New Method of X-ray Crystal Analysis|journal=Phys. Rev.|volume=10|page=661|doi=10.1103/PhysRev.10.661|issue=6|bibcode = 1917PhRv...10..661H }}</ref> The structure of graphite was determined from single-crystal diffraction in 1924 by two groups independently.<ref>{{cite journal| vauthors = Bernal JD|author-link=John Desmond Bernal|date = 1924|title=The Structure of Graphite|jstor=94336|journal= Proc. R. Soc. Lond.|volume=A106|issue=740|pages=749–773}}</ref><ref>{{cite journal| vauthors = Hassel O, Mack H |date = 1924|title=Über die Kristallstruktur des Graphits|journal=Zeitschrift für Physik|volume=25|issue=1|page=317|doi=10.1007/BF01327534|bibcode = 1924ZPhy...25..317H |s2cid=121157442}}</ref> Hull also used the powder method to determine the structures of various metals, such as iron<ref>{{cite journal|author=Hull AW|date = 1917|title=The Crystal Structure of Iron|journal=Phys. Rev.|volume=9|issue = 1|page=84|doi= 10.1103/PhysRev.9.83|bibcode = 1917PhRv....9...83. }}</ref> and magnesium.<ref>{{cite journal | vauthors = Hull AW | title = The Crystal Structure of Magnesium | journal = Proceedings of the National Academy of Sciences of the United States of America | volume = 3 | issue = 7 | pages = 470–473 | date = July 1917 | pmid = 16576242 | pmc = 1091290 | doi = 10.1073/pnas.3.7.470 | doi-access = free | bibcode = 1917PNAS....3..470H }}</ref>