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<h1 id="firstHeading" class="firstHeading mw-first-heading"><span class="mw-page-title-main">Trigonales Kristallsystem</span></h1>
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<div id="mw-content-text" class="mw-body-content mw-content-ltr" lang="de" dir="ltr"><div class="mw-content-ltr mw-parser-output" lang="de" dir="ltr"><p>Das <b>Trigonale Kristallsystem</b> gehört zu den sieben <a href="Kristallsystem" title="Kristallsystem">Kristallsystemen</a> in der <a href="Kristallographie" title="Kristallographie">Kristallographie</a>. Es umfasst alle <a href="Punktgruppe" title="Punktgruppe">Punktgruppen</a> mit einer drei<a href="Symmetrie_(Geometrie)#Rotationssymmetrie_/_Drehsymmetrie" title="Symmetrie (Geometrie)">zähligen</a> Dreh- oder <a href="Drehinversion" class="mw-redirect" title="Drehinversion">Drehinversions</a>achse.
</p><p>Das trigonale Kristallsystem ist mit dem <a href="Hexagonales_Kristallsystem" title="Hexagonales Kristallsystem">hexagonalen Kristallsystem</a> eng verwandt und bildet zusammen mit ihm die hexagonale <a href="Kristallfamilie" title="Kristallfamilie">Kristallfamilie</a>.
</p>
<div class="mw-heading mw-heading2"><h2 id="Trigonale_Achsensysteme">Trigonale Achsensysteme</h2></div>
<p>Zur Beschreibung trigonaler <a href="Raumgruppe" title="Raumgruppe">Raumgruppen</a> werden zwei verschiedene <a href="Gitter-System" class="mw-redirect" title="Gitter-System">Gitter-Systeme</a> verwendet:
</p>
<ul><li>das hexagonale Gitter-System</li>
<li>das rhomboedrische Gitter-System.</li></ul>
<p>Diese sind im Artikel <a href="Hexagonales_Kristallsystem" title="Hexagonales Kristallsystem">hexagonales Kristallsystem</a> beschrieben.
</p><p>Im modernen Sprachgebrauch sind die beiden Begriffe trigonal und rhomboedrisch klar abgegrenzt:
</p>
<ul><li>trigonal ist die Bezeichnung für eine Menge von <a href="Symmetriegruppe" title="Symmetriegruppe">Symmetriegruppen</a>.</li>
<li>rhomboedrisch ist die Bezeichnung eines Gitter-Systems.</li></ul>
<div class="mw-heading mw-heading2"><h2 id="Trigonale_Punktgruppen">Trigonale Punktgruppen</h2></div>
<p>Das trigonale Kristallsystem umfasst die Punktgruppen 3, <span style="text-decoration:overline">3</span>, 32, 3<i>m</i> und <span style="text-decoration:overline">3</span><i>m</i>. Dies sind alle Punktgruppen der hexagonalen Kristallfamilie, in denen es eine Raumgruppe <i>R</i>... mit rhomboedrischer <a href="Elementarzelle#Zentrierte_Elementarzelle" title="Elementarzelle">Zentrierung</a> gibt – dagegen können die Raumgruppen des hexagonalen Kristallsystems <i>alle</i> mit dem hexagonal primitiven Achsensystem beschrieben werden (<i>P</i>...).
</p><p>Das trigonale Kristallsystem umfasst somit alle Untergruppen der Punktgruppe <span style="text-decoration:overline">3</span><i>m</i>, die eine 3-zählige Achse haben; daher auch die charakteristische 3 (oder <span style="text-decoration:overline">3</span>) an zweiter Stelle der Raumgruppensymbole des trigonalen Kristallsystems. Diese Punktgruppen haben – anders als die hexagonalen Punktgruppen – alle eine kubische Obergruppe.
</p><p>Folgende Tabelle liefert einen Überblick über die Raumgruppen des trigonalen Kristallsystems:
</p>
<table class="wikitable centered">
<tbody><tr>
<th colspan="2">Punktgruppe
</th>
<th colspan="2">Raumgruppen (Hermann-Mauguin-Symbole)
</th></tr>
<tr>
<th><a href="Schoenflies-Symbol" class="mw-redirect" title="Schoenflies-Symbol">Schoenflies-<br>Symbol</a>
</th>
<th><a href="Hermann-Mauguin-Symbol" class="mw-redirect" title="Hermann-Mauguin-Symbol">Hermann-Mauguin-<br>Symbol</a>
</th>
<th>primitiv
</th>
<th>zentriert
</th></tr>
<tr>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{3}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{3}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/66e9abeb5057b7afbf88e3169101849354f13c65.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.716ex; height:2.509ex;" alt="{\displaystyle C_{3}}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 3}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mn>3</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle 3}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/991e33c6e207b12546f15bdfee8b5726eafbbb2f.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.162ex; height:2.176ex;" alt="{\displaystyle 3}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P3,\,P3_{1},\,P3_{2}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>P</mi>
<mn>3</mn>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<msub>
<mn>3</mn>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<msub>
<mn>3</mn>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P3,\,P3_{1},\,P3_{2}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/ca2c72dbf83b404fef260858b6d8674026a6fc1d.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:13.674ex; height:2.509ex;" alt="{\displaystyle P3,\,P3_{1},\,P3_{2}}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R3}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>R</mi>
<mn>3</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle R3}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/567a7a47713bedeff2b52d3b076afc3909c9eaaf.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.926ex; height:2.176ex;" alt="{\displaystyle R3}" loading="lazy"></span>
</td></tr>
<tr>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{3i}(\equiv S_{6})}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
<mi>i</mi>
</mrow>
</msub>
<mo stretchy="false">(</mo>
<mo>≡<!-- ≡ --></mo>
<msub>
<mi>S</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>6</mn>
</mrow>
</msub>
<mo stretchy="false">)</mo>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{3i}(\equiv S_{6})}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/ec7b2feb0630a163ae4b6197f9e5c90a1b85dd7c.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.838ex; width:10.025ex; height:2.843ex;" alt="{\displaystyle C_{3i}(\equiv S_{6})}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\bar {3}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\bar {3}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/8ebdfe153ce5f42ce15afe62d96dcdac78131d4d.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:1.162ex; height:2.509ex;" alt="{\displaystyle {\bar {3}}}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P{\bar {3}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P{\bar {3}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/b5d74379d253ac4bb81e39c9809aa8f0185c0541.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.908ex; height:2.509ex;" alt="{\displaystyle P{\bar {3}}}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R{\bar {3}}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle R{\bar {3}}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/f0c02ba0e348256425d0ed7b762d2cbc337d77f0.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.926ex; height:2.509ex;" alt="{\displaystyle R{\bar {3}}}" loading="lazy"></span>
</td></tr>
<tr>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle D_{3}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle D_{3}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/c58ecc2f3bfa64c9a31f2a459205efd74082a824.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:2.979ex; height:2.509ex;" alt="{\displaystyle D_{3}}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 32}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mn>32</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle 32}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/a28cd1505cccfe738e9c90499f48ef42bf2ed5c7.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:2.325ex; height:2.176ex;" alt="{\displaystyle 32}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P312,\,P321,\,P3_{1}12,\,P3_{1}21\,P3_{2}12,\,P3_{2}21}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>P</mi>
<mn>312</mn>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<mn>321</mn>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<msub>
<mn>3</mn>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mn>12</mn>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<msub>
<mn>3</mn>
<mrow class="MJX-TeXAtom-ORD">
<mn>1</mn>
</mrow>
</msub>
<mn>21</mn>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<msub>
<mn>3</mn>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mn>12</mn>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<msub>
<mn>3</mn>
<mrow class="MJX-TeXAtom-ORD">
<mn>2</mn>
</mrow>
</msub>
<mn>21</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P312,\,P321,\,P3_{1}12,\,P3_{1}21\,P3_{2}12,\,P3_{2}21}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/ced3f885918da471891712e5b5485381c21d7f85.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:41.685ex; height:2.509ex;" alt="{\displaystyle P312,\,P321,\,P3_{1}12,\,P3_{1}21\,P3_{2}12,\,P3_{2}21}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R32}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>R</mi>
<mn>32</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle R32}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/ebd8f0391a5325fe875b749ed5b81b075f014af6.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:4.089ex; height:2.176ex;" alt="{\displaystyle R32}" loading="lazy"></span>
</td></tr>
<tr>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle C_{3v}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>C</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
<mi>v</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle C_{3v}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/ba273a2d71fc53580ce7d217d47212ae37424d77.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.513ex; height:2.509ex;" alt="{\displaystyle C_{3v}}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle 3m}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mn>3</mn>
<mi>m</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle 3m}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/5b4a9d9a394c2649d35d628ccdf4226e47ed7d24.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:3.203ex; height:2.176ex;" alt="{\displaystyle 3m}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P3m1,\,P31m,\,P3c1,\,P31c}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>P</mi>
<mn>3</mn>
<mi>m</mi>
<mn>1</mn>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<mn>31</mn>
<mi>m</mi>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<mn>3</mn>
<mi>c</mi>
<mn>1</mn>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<mn>31</mn>
<mi>c</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P3m1,\,P31m,\,P3c1,\,P31c}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/3ad07a62425f77450ad287df229ac464a3685e7a.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:26.639ex; height:2.509ex;" alt="{\displaystyle P3m1,\,P31m,\,P3c1,\,P31c}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R3m,\,R3c}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>R</mi>
<mn>3</mn>
<mi>m</mi>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>R</mi>
<mn>3</mn>
<mi>c</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle R3m,\,R3c}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/15feb5ddc4706916524a4f4f3cafbef34cee0007.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:10.321ex; height:2.509ex;" alt="{\displaystyle R3m,\,R3c}" loading="lazy"></span>
</td></tr>
<tr>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle D_{3d}}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<msub>
<mi>D</mi>
<mrow class="MJX-TeXAtom-ORD">
<mn>3</mn>
<mi>d</mi>
</mrow>
</msub>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle D_{3d}}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/18971dcc6f527127237173db1896ec072e2eed78.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:3.838ex; height:2.509ex;" alt="{\displaystyle D_{3d}}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle {\bar {3}}m}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
<mi>m</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle {\bar {3}}m}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/1ee24791c6045b98a801d41dbad43e16639a501d.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.338ex; width:3.203ex; height:2.509ex;" alt="{\displaystyle {\bar {3}}m}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle P{\bar {3}}1m,\,P{\bar {3}}1c,\,P{\bar {3}}1c,\,P{\bar {3}}c1}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
<mn>1</mn>
<mi>m</mi>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
<mn>1</mn>
<mi>c</mi>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
<mn>1</mn>
<mi>c</mi>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>P</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
<mi>c</mi>
<mn>1</mn>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle P{\bar {3}}1m,\,P{\bar {3}}1c,\,P{\bar {3}}1c,\,P{\bar {3}}c1}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/82414d6fe845c47393dcd02c3693196313f62281.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:25.605ex; height:2.843ex;" alt="{\displaystyle P{\bar {3}}1m,\,P{\bar {3}}1c,\,P{\bar {3}}1c,\,P{\bar {3}}c1}" loading="lazy"></span></td>
<td><span class="mwe-math-element mwe-math-element-inline"><span class="mwe-math-mathml-inline mwe-math-mathml-a11y" style="display: none;"><math xmlns="http://www.w3.org/1998/Math/MathML" alttext="{\displaystyle R{\bar {3}}m,\,R{\bar {3}}c}">
<semantics>
<mrow class="MJX-TeXAtom-ORD">
<mstyle displaystyle="true" scriptlevel="0">
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
<mi>m</mi>
<mo>,</mo>
<mspace width="thinmathspace"></mspace>
<mi>R</mi>
<mrow class="MJX-TeXAtom-ORD">
<mrow class="MJX-TeXAtom-ORD">
<mover>
<mn>3</mn>
<mo stretchy="false">¯<!-- ¯ --></mo>
</mover>
</mrow>
</mrow>
<mi>c</mi>
</mstyle>
</mrow>
<annotation encoding="application/x-tex">{\displaystyle R{\bar {3}}m,\,R{\bar {3}}c}</annotation>
</semantics>
</math></span><img src="./_assets_/eb734a37dd21ce173a46342d1cc64c92/84e6912a6c6e6fcb7fd594b3e8ebb6183cd82858.svg" class="mwe-math-fallback-image-inline mw-invert skin-invert" aria-hidden="true" style="vertical-align: -0.671ex; width:10.321ex; height:2.843ex;" alt="{\displaystyle R{\bar {3}}m,\,R{\bar {3}}c}" loading="lazy"></span>
</td></tr>
</tbody></table>
<div class="mw-heading mw-heading3"><h3 id="Physikalische_Eigenschaften">Physikalische Eigenschaften</h3></div>
<p>Zur Beschreibung der trigonalen Kristallklassen in <a href="Hermann-Mauguin-Symbolik" title="Hermann-Mauguin-Symbolik">Hermann-Mauguin-Symbolik</a> werden die Symmetrieoperationen bezüglich vorgegebener Richtungen im Gitter-System angegeben.
</p>
<ul><li>im hexagonalen Achsensystem:
<ul><li>1. Symbol in Richtung der c-Achse (<001>)</li>
<li>2. Symbol in Richtung einer a-Achse (<100>)</li>
<li>3. Symbol in einer Richtung senkrecht zu einer a- und der c-Achse (<120>). Für die 3. Richtung wird auch oftmals die im Allgemeinen <i>nicht</i> äquivalente Richtung <210> angegeben. Auch wenn dies speziell für die Angabe der Lage der Symmetrieelemente keine Rolle spielt, so entspricht diese Angabe nicht den Konventionen.</li></ul></li></ul>
<ul><li>im rhomboedrischen Achsensystem:
<ul><li>1. Symbol in Richtung der <a href="Raumdiagonale" class="mw-redirect" title="Raumdiagonale">Raumdiagonalen</a> (<111>)</li>
<li>2. Symbol in Richtung einer Flächendiagonalen (<1<span style="text-decoration:overline">1</span>0>).</li></ul></li></ul>
<table class="wikitable" style="text-align:center">
<tbody><tr class="hintergrundfarbe5">
<th colspan="8">Punktgruppe (Kristallklasse)
</th>
<th colspan="3">Physikalische Eigenschaften<sup id="cite_ref-Hinweise_1-0" class="reference"><a href="#cite_note-Hinweise-1"><span class="cite-bracket">[</span>Anm. 1<span class="cite-bracket">]</span></a></sup>
</th>
<th rowspan="3">Beispiele
</th></tr>
<tr class="hintergrundfarbe5">
<th rowspan="2">Nr.
</th>
<th rowspan="2"><a href="Kristallsystem" title="Kristallsystem">Kristallsystem</a>
</th>
<th rowspan="2">Name
</th>
<th rowspan="2"><a href="Schoenflies-Symbolik" title="Schoenflies-Symbolik">Schoenflies-Symbol</a>
</th>
<th colspan="2">Internationales Symbol<br>(<a href="Hermann-Mauguin-Symbolik" title="Hermann-Mauguin-Symbolik">Hermann-Mauguin</a>)
</th>
<th rowspan="2"><a href="Lauegruppe" title="Lauegruppe">Laueklasse</a>
</th>
<th rowspan="2">Zugehörige<br><a href="Raumgruppe" title="Raumgruppe">Raumgruppen</a> (Nr.)
</th>
<th rowspan="2"><a href="Optische_Aktivit%C3%A4t" title="Optische Aktivität">Optische Aktivität</a> (<a href="Chiralit%C3%A4t_(Chemie)" title="Chiralität (Chemie)">Enantiomorphie</a>)
</th>
<th rowspan="2"><a href="Pyroelektrizit%C3%A4t" title="Pyroelektrizität">Pyroelektrizität</a>
</th>
<th rowspan="2"><a href="Piezoelektrizit%C3%A4t" title="Piezoelektrizität">Piezoelektrizität</a>; <a href="Frequenzverdopplung" title="Frequenzverdopplung">SHG-Effekt</a>
</th></tr>
<tr class="hintergrundfarbe5">
<th>Voll
</th>
<th>Kurz
</th></tr>
<tr>
<td>16
</td>
<td rowspan="5">trigonal
</td>
<td align="left">trigonal-pyramidal
</td>
<td><i>C</i><sub>3</sub>
</td>
<td>3
</td>
<td>3
</td>
<td rowspan="2"><span style="text-decoration:overline">3</span>
</td>
<td>143–146
</td>
<td>+
</td>
<td>+ [001]
</td>
<td>+
</td>
<td><a href="Carlinit" title="Carlinit">Carlinit</a><br><a href="Gratonit" title="Gratonit">Gratonit</a>
</td></tr>
<tr>
<td>17
</td>
<td align="left">rhomboedrisch
</td>
<td><i>C</i><sub>3<i>i</i></sub> (<i>S</i><sub>6</sub>)
</td>
<td><span style="text-decoration:overline">3</span>
</td>
<td><span style="text-decoration:overline">3</span>
</td>
<td>147–148
</td>
<td>–
</td>
<td>–
</td>
<td>–
</td>
<td><a href="Dolomit_(Mineral)" title="Dolomit (Mineral)">Dolomit</a><br><a href="Dioptas" title="Dioptas">Dioptas</a>
</td></tr>
<tr>
<td>18
</td>
<td align="left">trigonal-trapezoedrisch
</td>
<td><i>D</i><sub>3</sub>
</td>
<td>321 bzw. 312
</td>
<td>32
</td>
<td rowspan="3"><span style="text-decoration:overline">3</span><i>m</i>
</td>
<td>149–155
</td>
<td>+
</td>
<td>–
</td>
<td>+
</td>
<td><a href="Quarz" title="Quarz">Quarz</a><br><a href="Tellur" title="Tellur">Tellur</a>
</td></tr>
<tr>
<td>19
</td>
<td align="left">ditrigonal-pyramidal
</td>
<td><i>C</i><sub>3<i>v</i></sub>
</td>
<td>3<i>m</i>1 bzw. 31<i>m</i>
</td>
<td>3<i>m</i>
</td>
<td>156–161
</td>
<td>–
</td>
<td>+ [001]
</td>
<td>+
</td>
<td><a href="Turmalingruppe" title="Turmalingruppe">Turmalin</a><br><a href="Pyrargyrit" title="Pyrargyrit">Pyrargyrit</a>
</td></tr>
<tr>
<td>20
</td>
<td align="left">ditrigonal-skalenoedrisch
</td>
<td><i>D</i><sub>3<i>d</i></sub>
</td>
<td><span style="text-decoration:overline">3</span>2/<i>m</i>1 bzw. <span style="text-decoration:overline">3</span>12/<i>m</i>
</td>
<td><span style="text-decoration:overline">3</span><i>m</i>
</td>
<td>162–167
</td>
<td>–
</td>
<td>–
</td>
<td>–
</td>
<td><a href="Calcit" title="Calcit">Calcit</a><br><a href="Korund" title="Korund">Korund</a>
</td></tr>
<tr class="hintergrundfarbe1">
<td colspan="13" align="left">
<ol class="references" data-mw-group="Anm.">
<li id="cite_note-Hinweise-1"><span class="mw-cite-backlink"><a href="#cite_ref-Hinweise_1-0">↑</a></span> <span class="reference-text">Bei den Angaben zu den physikalischen Eigenschaften bedeutet:
<dl><dd>„<b>−</b>“ aufgrund der Symmetrie verboten</dd>
<dd>„<b>+</b>“ erlaubt.</dd></dl>
Über die Größenordnung der optischen Aktivität, Pyro- und Piezoelektrizität sowie des SHG-Effekts kann rein aufgrund der Symmetrie keine Aussage getroffen werden; man kann aber davon ausgehen, dass stets eine zumindest schwache Ausprägung der Eigenschaft vorhanden ist.<br>
Für die Pyroelektrizität ist, sofern vorhanden, auch die Richtung des pyroelektrischen Vektors angegeben.</span>
</li>
</ol>
</td></tr></tbody></table>
<p>Weitere trigonal kristallisierende chemische Stoffe siehe Kategorie:Trigonales Kristallsystem
</p>
<div class="mw-heading mw-heading2"><h2 id="Trigonale_Kristallformen">Trigonale Kristallformen</h2></div>
<div class="hauptartikel" role="navigation"><span class="hauptartikel-pfeil" title="siehe" aria-hidden="true" role="presentation">→ </span><i><span class="hauptartikel-text">Hauptartikel</span>: <a href="Kristallmorphologie" title="Kristallmorphologie">Kristallmorphologie</a></i></div>
<ul class="gallery mw-gallery-traditional">
<li class="gallerybox" style="width: 155px">
<div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"></span></div>
<div class="gallerytext">Ditrigonales <a href="Skalenoeder" title="Skalenoeder">Skalenoeder</a></div>
</li>
<li class="gallerybox" style="width: 155px">
<div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"></span></div>
<div class="gallerytext">Trigonales <a href="Trapezoeder" title="Trapezoeder">Trapezoeder</a></div>
</li>
<li class="gallerybox" style="width: 155px">
<div class="thumb" style="width: 150px; height: 150px;"><span typeof="mw:File"></span></div>
<div class="gallerytext"><a href="Quarz" title="Quarz">Quarzkristall</a></div>
</li>
</ul>
<div class="mw-heading mw-heading2"><h2 id="Siehe_auch">Siehe auch</h2></div>
<ul><li><a href="Wirteliges_Kristallsystem" title="Wirteliges Kristallsystem">Wirteliges Kristallsystem</a></li></ul>
<div class="mw-heading mw-heading2"><h2 id="Literatur">Literatur</h2></div>
<ul><li>W. Borchardt-Ott: <i>Kristallographie.</i> 6. Auflage. Springer, Berlin 2002, ISBN 3-540-43964-1.</li>
<li>W. Massa: <i>Kristallstrukturbestimmung.</i> 3. Auflage. Teubner, Stuttgart 2002, ISBN 3-519-23527-7.</li>
<li>M. Okrusch, S. Matthes: <i>Mineralogie.</i> 7. Auflage. Springer, Berlin 2005, ISBN 3-540-23812-3.</li>
<li>Hahn, Theo (Hrsg.): <i><a href="International_Tables_for_Crystallography" title="International Tables for Crystallography">International Tables for Crystallography</a> Vol. A</i> D. Reidel publishing Company, Dordrecht 1983, ISBN 90-277-1445-2</li></ul>
<div class="mw-heading mw-heading2"><h2 id="Weblinks">Weblinks</h2></div>
<ul><li><i><a rel="nofollow" class="external text" href="https://fsmath.mathematik.tu-dortmund.de/Skripte/kreuzer/Algebra_I_2004-10-16_letzte-Fassung.pdf#page=11">Kurzskript Algebra I – Kristallographie</a>.</i> Uni Dortmund, S. 11 (PDF, 412 kB).</li></ul>
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<div class="klappleiste-kopf">Die sieben <a href="Kristallsystem" title="Kristallsystem">Kristallsysteme</a></div>
<div class="klappleiste-inhalt mw-collapsible-content">
<p><a href="Triklines_Kristallsystem" title="Triklines Kristallsystem">triklin</a> |
<a href="Monoklines_Kristallsystem" title="Monoklines Kristallsystem">monoklin</a> |
<a href="Orthorhombisches_Kristallsystem" title="Orthorhombisches Kristallsystem">orthorhombisch</a> |
<a href="Tetragonales_Kristallsystem" title="Tetragonales Kristallsystem">tetragonal</a> |
<a class="mw-selflink selflink">trigonal</a> |
<a href="Hexagonales_Kristallsystem" title="Hexagonales Kristallsystem">hexagonal</a> |
<a href="Kubisches_Kristallsystem" title="Kubisches Kristallsystem">kubisch</a>
</p>
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