No. 12 C 1 2/m 1

Number

12

Hermann–Mauguin symbol

C 1 2/m 1

Hall symbol

-C 2y

Crystal system

Monoclinic

Operations per cell

8

General position

8j (site symmetry 1)

Wyckoff positions (standard setting)

How to read it

• Each symmetry element drawn in the cell is worked out from the group’s operations: rotation and screw axes as lines (arrow = direction; dashed = screw), mirror and glide planes as sheets (dashed outline = glide), inversion centres as dots; rotoinversion axes are dotted. Colours: 2-fold red, 3-fold green, 4-fold blue, 6-fold purple.
• The multiplicity is how many equivalent points an atom on that site generates in the conventional cell; the general position has the highest multiplicity, equal to the number of operations.
• Site symmetry is the point group that leaves that position fixed; a special position (lower multiplicity) sits on a symmetry element — press + on a row to see its atoms land on the drawn elements.

Crystal Lab structures in this group

• Yttrium trichloride (YCl₃) — Layered AB₃ (ccp anions)

Prototype structures in this group (79)

Au₁₁Mn₃Nb₁₂O₂₉Al₁₃Fe₄Al₁₃Os₄BiNiCl₂H₁₂MgO₆ J17Ca₂H₂Mg₅O₂₄Si₈ S42Co₂Ge₄Pr₅Ga₂O₃As₂Te₃Au₂P₃K₂O₅Ti₂Cu₂O₅SNa₂O₇U₂Li₂MnO₃C₂CaBi₂PdGe₂OsNb₂SeCl₂CuAg₃Ir₂LiO₆As₃Mo₂Cl₃Gd₂Ni₃Sn₄ D7aCr₃S₄Rh₃S₄Li₃O₆SbZn₂H₃LiO₂ B36Al₄₅V₇C₄RhSc₃Ni₄PuAl₅Fe₂H₂O₁₂Si₂Au₅Mn₂Cr₅Se₈TlO₆PbV₂Mn₇O₁₂PrO₇Sc₂Si₂ S21F₇Ho₂KNb₇P₄S₇Y₅Cr₇Se₈H₈K₂MnO₁₂S₂ H423Al₈Mo₃S₈V₅CoZn₁₃FeSe₂TlRuU₂NbTe₂AuTe₂ C34NiO₂HgO₂ClHg₃IS₂BaO₃PbAlCl₃BaMn₂O₄AsPd₅MgZn₅ D22(H₂O)Mg₆O₁₁(OH)₆Si₄ S45NiO₆Sr₂TePdSe₆Ta₂AlKO₈Si₃ S67AlLiO₂NaNiO₂MnPS₃BaIrO₃BaIrO₃AlNbO₄BrCGdNSrBiIBiICoGeAlCuAsSiBiIClZrCPuO