-    NININGERITE     -    MgS

Niningerite: this is the Mg end-member term of the MgS-Cas solid solution with ordered super-structure. Because of symmetry, there is no Raman-active mode; all the modes are InfraRed-active. See article for details

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:  225  Fm-3m 
Lattice parameters (Å):       
Angles (°):       

Symmetry (theoretical): 

Space group:  225  Fm-3m 
Lattice parameters (Å):  5.1144  5.1144  5.1144 
Angles (°):  60  60  60 

Cell contents: 

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

Atomic positions (theoretical):

Mg:  0.0000  0.0000  0.0000 
S:  0.0000  0.0000  0.0000 
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: 


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: 2.2603 0.0000 0.0000 
0.0000 2.2603 0.0000 
0.0000 0.0000 2.2603 
Eig. Value: 2.2603 2.2603 2.2603 
S: -2.2603 -0.0000 -0.0000 
-0.0000 -2.2603 -0.0000 
-0.0000 -0.0000 -2.2603 
Eig. Value: -2.2603 -2.2603 -2.2603 
Atom type 

Dielectric tensors: 

Ɛ5.5099 0.0000 0.0000 
0.0000 5.5099 0.0000 
0.0000 0.0000 5.5099 
Eig. Value: 5.5099 5.5099 5.5099 
Refractive index (N): 2.3473 0.0000 0.0000 
0.0000 2.3473 0.0000 
0.0000 0.0000 2.3473 
Eig. Value: 2.3473 2.3473 2.3473 
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