-    LORENZENITE     -    Na2Ti2Si2O9

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:  60  Pbcn 
Lattice parameters (Å):  11.8063  11.8063  11.8063 
Angles (°):  90  90  90 

Symmetry (theoretical): 

Space group:  60  Pbcn 
Lattice parameters (Å):  8.5572  5.1506  14.1978 
Angles (°):  90  90  90 

Cell contents: 

Number of atoms:  60 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Na:  0.0596  0.6411  0.1527 
Ti:  0.1532  0.1311  0.3295 
Si:  0.3426  0.2991  0.5273 
O:  1.0000  0.9978  0.2500 
O:  0.1782  0.4473  0.2744 
O:  0.3330  0.2989  0.4147 
O:  0.0102  0.2455  0.4281 
O:  0.2335  0.0648  0.5690 
Na:  0.4404  0.8589  0.6527 
Ti:  0.3468  0.3689  0.8295 
Si:  0.1574  0.2009  0.0273 
O:  0.5000  0.5022  0.7500 
O:  0.3218  0.0527  0.7744 
O:  0.1670  0.2011  0.9147 
O:  0.4898  0.2545  0.9281 
O:  0.2665  0.4352  0.0690 
Na:  0.9404  0.6411  0.3473 
Ti:  0.8468  0.1311  0.1705 
Si:  0.6574  0.2991  0.9727 
O:  0.8218  0.4473  0.2256 
O:  0.6670  0.2989  0.0853 
O:  0.9898  0.2455  0.0719 
O:  0.7665  0.0648  0.9310 
Na:  0.5596  0.8589  0.8473 
Ti:  0.6532  0.3689  0.6705 
Si:  0.8426  0.2009  0.4727 
O:  0.6782  0.0527  0.7256 
O:  0.8330  0.2011  0.5853 
O:  0.5102  0.2545  0.5719 
O:  0.7335  0.4352  0.4310 
Na:  0.9404  0.3589  0.8473 
Ti:  0.8468  0.8689  0.6705 
Si:  0.6574  0.7009  0.4727 
O:  1.0000  0.0022  0.7500 
O:  0.8218  0.5527  0.7256 
O:  0.6670  0.7011  0.5853 
O:  0.9898  0.7545  0.5719 
O:  0.7665  0.9352  0.4310 
Na:  0.5596  0.1411  0.3473 
Ti:  0.6532  0.6311  0.1705 
Si:  0.8426  0.7991  0.9727 
O:  0.5000  0.4978  0.2500 
O:  0.6782  0.9473  0.2256 
O:  0.8330  0.7989  0.0853 
O:  0.5102  0.7455  0.0719 
O:  0.7335  0.5648  0.9310 
Na:  0.0596  0.3589  0.6527 
Ti:  0.1532  0.8689  0.8295 
Si:  0.3426  0.7009  0.0273 
O:  0.1782  0.5527  0.7744 
O:  0.3330  0.7011  0.9147 
O:  0.0102  0.7545  0.9281 
O:  0.2335  0.9352  0.0690 
Na:  0.4404  0.1411  0.1527 
Ti:  0.3468  0.6311  0.3295 
Si:  0.1574  0.7991  0.5273 
O:  0.3218  0.9473  0.2744 
O:  0.1670  0.7989  0.4147 
O:  0.4898  0.7455  0.4281 
O:  0.2665  0.5648  0.5690 
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.
 

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: 176
k-points  
   grid: 2 4 1 
   number of shifts: 
   shifts: 0.5 0.5 0.5 
Kinetic energy cut-off: 40 Ha  [=1088.464 eV ]
eXchange-Correlation functional: LDA pw90 

Pseudopotentials: 
Na:  sodium, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local 
Ti:  Tetter norm-conserving pseudopotential 
Si:  silicon, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local 
O:  oxygen, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local