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PHY.K02UF Molecular and Solid State Physics | ||||
Perovskite is a crystal structure with a simple cubic Bravais lattice and five atoms in the basis. The cubic form is typically the high temperature phase of perovskite compounds. They often go through a structural phase transition to a tetragonal phase or some other phase with lower symmetry. Perovskites are often ferroelectrics, piezoelectrics, and pyroelectrics. They can have very high dielectric constants and are used in supercapacitors. There are perovskite superconductors and they have promising applications in solar cells.
Crystal structure: Perovskite
Bravais lattice: Simple cubic
Space group: 221 ($Pm\overline{3}m$), Strukturbericht: E21, Pearson symbol: cP5
Point group: m3m (Oh) six 2-fold rotations, four 3-fold rotations, three 4-fold rotations, nine mirror planes, inversion
The lattice parameters of the conventional unit cell are:
\[ \begin{equation} a = b = c, \hspace{0.5cm} \alpha = 90^{\circ} , \,\beta = 90^{\circ} ,\,\gamma = 90^{\circ} . \end{equation} \]The primitive unit cell is the same as the conventional unit cell. The primitive lattice vectors are,
$\vec{a}_1=a\hat{x}$, $\vec{a}_2=a\hat{y}$, $\vec{a}_3=a\hat{z}$.
There are three atoms in asymmetric unit,
Ca (0,0,0), Ti (0.5,0.5,0.5), O (0.5,0.5,0),
and five atoms in the basis,
Ca (0,0,0), Ti (0.5,0.5,0.5), O (0.5,0.5,0), O (0.5,0,0.5), O (0,0.5,0.5).
Space group: 221 ($Pm\overline{3}m$)
48 symmetry operations:
1 x,y,z identity 2 -x,-y,z C2 axis 3 -x,y,-z C2 axis 4 x,-y,-z C2 axis 5 z,x,y C3 axis 6 z,-x,-y C3 axis 7 -z,-x,y C3 axis 8 -z,x,-y C3 axis 9 y,z,x C3 axis 10 -y,z,-x C3 axis 11 y,-z,-x C3 axis 12 -y,-z,x C3 axis 13 y,x,-z C2 axis 14 -y,-x,-z C2 axis 15 y,-x,z C4 axis 16 -y,x,z C4 axis 17 x,z,-y C4 axis 18 -x,z,y C2 axis 19 -x,-z,-y C2 axis 20 x,-z,y C4 axis 21 z,y,-x C4 axis 22 z,-y,x C2 axis 23 -z,y,x C4 axis 24 -z,-y,-x C2 axis 25 -x,-y,-z Ci: 0 0 0 26 x,y,-z mirror plane 27 x,-y,z mirror plane 28 -x,y,z mirror plane 29 -z,-x,-y 3-bar axis|inversion center at 0 0 0 30 -z,x,y 3-bar axis|inversion center at 0 0 0 31 z,x,-y 3-bar axis|inversion center at 0 0 0 32 z,-x,y 3-bar axis|inversion center at 0 0 0 33 -y,-z,-x 3-bar axis|inversion center at 0 0 0 34 y,-z,x 3-bar axis|inversion center at 0 0 0 35 -y,z,x 3-bar axis|inversion center at 0 0 0 36 y,z,-x 3-bar axis|inversion center at 0 0 0 37 -y,-x,z mirror plane 38 y,x,z mirror plane 39 -y,x,-z 4-bar axis|inversion center at 0 0 0 40 y,-x,-z 4-bar axis|inversion center at 0 0 0 41 -x,-z,y 4-bar axis|inversion center at 0 0 0 42 x,-z,-y mirror plane 43 x,z,y mirror plane 44 -x,z,-y 4-bar axis|inversion center at 0 0 0 45 -z,-y,x 4-bar axis|inversion center at 0 0 0 46 -z,y,-x mirror plane 47 z,-y,-x 4-bar axis|inversion center at 0 0 0 48 z,y,x mirror plane