-    GEIKIELITE     -    MgTiO3

 

Crystal Structure 


Because of the translational symmetry all the calculations are performed in the primitive unit cell and not in the conventional unit cell. The following information regarding the structure is given with respect to this primitive unit cell, which sometimes can take an unintuitive shape.

Symmetry (experimental): 

Space group:  148  R-3 
Lattice parameters (Å):  5.0567  5.0567  13.9034 
Angles (°):  90.0  90.0  120.0 

Symmetry (theoretical): 

Space group:  148  R-3 
Lattice parameters (Å):  5.3784  5.3784  5.3784 
Angles (°):  55.3  55.3  55.3 

Cell contents: 

Number of atoms:  10 
Number of atom types:  3 
Chemical composition:  0 

Atomic positions (theoretical):

Mg:  0.3547  0.3547  0.3547 
Ti:  0.1446  0.1446  0.1446 
O:  0.5605  0.9522  0.2289 
O:  0.9522  0.2289  0.5605 
O:  0.2289  0.5605  0.9522 
Mg:  0.6453  0.6453  0.6453 
Ti:  0.8554  0.8554  0.8554 
O:  0.4395  0.0478  0.7711 
O:  0.0478  0.7711  0.4395 
O:  0.7711  0.4395  0.0478 
Atom type  X  Y  Z 

We have listed here the reduced coordinates of all the atoms in the primitive unit cell.
It is enough to know only the position of the atoms from the assymetrical unit cell and then use the symmetry to build the whole crystal structure.

Visualization of the crystal structure: 

Size:

 Nx:  Ny:  Nz: 
You can define the size of the supercell to be displayed in the jmol panel as integer translations along the three crys­tallo­gra­phic axis.
Please note that the structure is represented using the pri­mi­tive cell, and not the conventional one.
 

Dielectric Properties 


We define:

  • The Born effective charges, also called dynamical charges, are tensors that correspond to the energy derivative with respect to atomic displacements and electric fields or, equivalently, to the change in atomic force due to an electric field: The sum of the Born effective charges of all nuclei in one cell must vanish, element by element, along each of the three directions of the space.
  • The dielectric tensors are the energy derivative with respect to two electric fields. They also relate the induced polarization to the external electric field.

Born effective charges (Z): 

Mg: 2.2128 -0.0338 0.0000 
0.0338 2.2128 0.0000 
-0.0000 0.0000 2.6680 
Eig. Value: 2.2128 2.2128 2.6680 
Ti: 5.5531 -0.0428 -0.0000 
0.0428 5.5527 0.0002 
-0.0001 0.0002 2.8993 
Eig. Value: 5.5531 5.5527 2.8993 
O: -2.7736 -0.9143 -0.0327 
-0.9653 -2.4034 0.4954 
-0.0516 0.5160 -1.8554 
Eig. Value: -3.5968 -1.2967 -2.1389 
O: -1.6823 0.3353 0.4456 
0.2842 -3.4950 -0.2195 
0.4730 -0.2134 -1.8559 
Eig. Value: -1.2967 -3.5969 -2.1395 
O: -3.3102 0.6556 -0.4129 
0.6045 -1.8671 -0.2761 
-0.4213 -0.3028 -1.8560 
Eig. Value: -3.5970 -1.2968 -2.1394 
Mg: 2.2128 -0.0338 0.0000 
0.0338 2.2128 0.0000 
-0.0000 0.0000 2.6680 
Eig. Value: 2.2128 2.2128 2.6680 
Ti: 5.5531 -0.0428 -0.0000 
0.0428 5.5527 0.0002 
-0.0001 0.0002 2.8993 
Eig. Value: 5.5531 5.5527 2.8993 
O: -2.7736 -0.9143 -0.0327 
-0.9653 -2.4034 0.4954 
-0.0516 0.5160 -1.8554 
Eig. Value: -3.5968 -1.2967 -2.1389 
O: -1.6823 0.3353 0.4456 
0.2842 -3.4950 -0.2195 
0.4730 -0.2134 -1.8559 
Eig. Value: -1.2967 -3.5969 -2.1395 
O: -3.3102 0.6556 -0.4129 
0.6045 -1.8671 -0.2761 
-0.4213 -0.3028 -1.8560 
Eig. Value: -3.5970 -1.2968 -2.1394 
Atom type  X  Y  Z 

Dielectric tensors: 

 X Y Z 
Ɛ∞: 5.1469 0.0000 0.0000 
0.0000 5.1464 0.0000 
0.0000 0.0000 3.8901 
Eig. Value: 5.1469 5.1464 3.8901 
Refractive index (N): 2.2687 0.0000 0.0000 
0.0000 2.2686 0.0000 
0.0000 0.0000 1.9723 
Eig. Value: 2.2687 2.2686 1.9723 
Ɛ0: 0.0000 0.0000 0.0000 
0.0000 0.0000 0.0000 
0.0000 0.0000 0.0000 
Eig. Value: 0.0000 0.0000 0.0000