-    GRAPHITE     -    C

The crystal structure is fully relaxed (both unit cell parameters and atomic positions under symmetry constraints) starting from an experimental structure similar to the one reported in AMCSD 

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:  186  P6_3mc 
Lattice parameters (Å):  2.4700  2.4700  6.7900 
Angles (°):  90  90  120 

Symmetry (theoretical): 

Space group:  186  P6_3mc 
Lattice parameters (Å):  2.4508  2.4508  6.6187 
Angles (°):  90  90  120 

Cell contents: 

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

Atomic positions (theoretical):

C:  0.0000  0.0000  0.0025 
C:  0.0000  0.0000  0.5025 
C:  0.3333  0.6667  0.0025 
C:  0.6667  0.3333  0.5025 
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): 

C: 0.2083 -0.0000 0.0000 
-0.0000 0.2083 -0.0000 
-0.0000 0.0000 0.0800 
Eig. Value: 0.2083 0.2083 0.0800 
C: 0.2083 -0.0000 -0.0000 
0.0000 0.2083 0.0000 
0.0000 -0.0000 0.0800 
Eig. Value: 0.2083 0.2083 0.0800 
C: -0.2083 0.0000 0.0000 
0.0000 -0.2083 -0.0000 
-0.0000 -0.0000 -0.0800 
Eig. Value: -0.2083 -0.2083 -0.0800 
C: -0.2083 0.0000 -0.0000 
-0.0000 -0.2083 0.0000 
0.0000 0.0000 -0.0800 
Eig. Value: -0.2083 -0.2083 -0.0800 
Atom type 

Dielectric tensors: 

 
Ɛ15.2881 0.0000 0.0000 
0.0000 15.2881 0.0000 
0.0000 0.0000 3.4330 
Eig. Value: 15.2881 15.2881 3.4330 
Refractive index (N): 3.9100 0.0000 0.0000 
0.0000 3.9100 0.0000 
0.0000 0.0000 1.8528 
Eig. Value: 3.9100 3.9100 1.8528 
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