-    GEIKIELITE     -    MgTiO3

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:  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: 
Chemical composition: 

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 

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.

Parameters of the Calculation 

All the calculations have been done using the ABINIT software. This is a list of the most representative parameteres used during the Raman calculation.

Number of electronic bands: 26
   grid: 6 6 4 
   number of shifts: 
   shifts: 0.5 0.5 0.5 
Kinetic energy cut-off: 32/54 Ha  [=870.7712 eV ]
eXchange-Correlation functional:  

Mg:  magnesium, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local 
Ti:  Titane.ion 3s2.3p6.4s0.3d2 rcd=1.65, rcs=rc0=1.25, ecut 32/54 
O:  oxygen, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local