-    Na2Mg(SO4)2     -    Na2Mg(SO4)2

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 ICSD database; code 249878 

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:  15  C2/c 
Lattice parameters (Å):  10.1010  8.2400  8.7300 
Angles (°):  90.0  114.640  90.0 

Symmetry (theoretical): 

Space group:  15  C2/c 
Lattice parameters (Å):  6.2840  6.2840  8.6606 
Angles (°):  67.88  112.11  101.71 

Cell contents: 

Number of atoms:  26 
Number of atom types:  4 
Chemical composition:  0 

Atomic positions (theoretical):

Mg:  0.0933  0.0933  0.2500 
Na:  0.3968  0.6686  0.0591 
S:  0.6083  0.9833  0.3171 
O:  0.7501  0.0269  0.4826 
O:  0.4114  0.1295  0.2304 
O:  0.5270  0.7398  0.3485 
O:  0.7445  0.0518  0.1980 
Na:  0.6686  0.3968  0.4409 
S:  0.9833  0.6083  0.1829 
O:  0.0269  0.7501  0.0174 
O:  0.1295  0.4114  0.2696 
O:  0.7398  0.5270  0.1515 
O:  0.0518  0.7445  0.3020 
Mg:  0.9067  0.9067  0.7500 
Na:  0.6032  0.3314  0.9409 
S:  0.3917  0.0167  0.6829 
O:  0.2499  0.9731  0.5174 
O:  0.5886  0.8705  0.7696 
O:  0.4730  0.2602  0.6515 
O:  0.2555  0.9482  0.8020 
Na:  0.3314  0.6032  0.5591 
S:  0.0167  0.3917  0.8171 
O:  0.9731  0.2499  0.9826 
O:  0.8705  0.5886  0.7304 
O:  0.2602  0.4730  0.8485 
O:  0.9482  0.2555  0.6980 
Atom type  X  Y  Z 

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: 26
k-points  
   grid: 4 4 4 
   number of shifts: 1 
   shifts: 0.5 0.5 0.5 
Kinetic energy cut-off: 40 Ha  [=1088.464 eV ]
eXchange-Correlation functional: LDA pw90 

Pseudopotentials: 
O:  oxygen, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local 
Na:  sodium, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local 
Mg:  magnesium, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local 
S:  sulphur, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 2 local