-    SKIPPENITE     -    Bi2Se2Te

 

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:  166  R-3m 
Lattice parameters (Å):  2.2135  2.2135  15.4186 
Angles (°):  90.0  90.0  120.0 

Symmetry (theoretical): 

Space group:  166  R-3m 
Lattice parameters (Å):  10.0592  10.0592  10.0592 
Angles (°):  23.9  23.9  23.9 

Cell contents: 

Number of atoms: 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Bi:  0.4037  0.4037  0.4037 
Se:  0.2117  0.2117  0.2117 
Te:  0.0000  0.0000  0.0000 
Bi:  0.5963  0.5963  0.5963 
Se:  0.7883  0.7883  0.7883 
Atom type 

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): 

Bi: 7.2062 0.0000 0.0000 
0.0000 7.2062 -0.0000 
0.0000 0.0000 2.3603 
Eig. Value: 7.2062 7.2062 2.3603 
Se: -4.7967 -0.0000 -0.0000 
-0.0000 -4.7967 0.0000 
-0.0000 -0.0000 -0.6653 
Eig. Value: -4.7967 -4.7967 -0.6653 
Te: -4.8190 0.0000 0.0000 
0.0000 -4.8190 -0.0000 
0.0000 0.0000 -3.3899 
Eig. Value: -4.8190 -4.8190 -3.3899 
Bi: 7.2062 0.0000 0.0000 
0.0000 7.2062 -0.0000 
0.0000 0.0000 2.3603 
Eig. Value: 7.2062 7.2062 2.3603 
Se: -4.7967 -0.0000 -0.0000 
-0.0000 -4.7967 0.0000 
-0.0000 -0.0000 -0.6653 
Eig. Value: -4.7967 -4.7967 -0.6653 
Atom type 

Dielectric tensors: 

 
Ɛ29.1962 0.0000 0.0000 
0.0000 29.1962 0.0000 
0.0000 0.0000 18.7867 
Eig. Value: 29.1962 29.1962 18.7867 
Refractive index (N): 5.4033 -0.0000 -0.0000 
-0.0000 5.4033 -0.0000 
-0.0000 -0.0000 4.3344 
Eig. Value: 5.4033 5.4033 4.3344 
Ɛ00.0000 0.0000 0.0000 
0.0000 0.0000 0.0000 
0.0000 0.0000 0.0000 
Eig. Value: 0.0000 0.0000 0.0000