-    PARALSTONITE     -    BaCa(CO3)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 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:  150  P321 
Lattice parameters (Å):  8.6920  8.6920  6.1480 
Angles (°):  90  90  120 

Symmetry (theoretical): 

Space group:  150  P321 
Lattice parameters (Å):  8.6043  8.6043  5.9690 
Angles (°):  90  90  120 

Cell contents: 

Number of atoms:  30 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Ba:  0.6886  1.0000  0.0000 
Ca:  0.3637  1.0000  0.5000 
C:  0.3333  0.6667  0.3569 
C:  0.3333  0.6667  0.8213 
C:  0.0000  1.0000  0.2636 
O:  0.1907  0.6780  0.3607 
O:  0.1786  0.5247  0.8240 
O:  0.1505  0.0045  0.2566 
Ba:  0.3114  0.3114  0.0000 
Ca:  0.6363  0.6363  0.5000 
O:  0.4873  0.8093  0.3607 
O:  0.3460  0.8214  0.8240 
O:  0.8540  0.8495  0.2566 
Ba:  0.0000  0.6886  0.0000 
Ca:  0.0000  0.3637  0.5000 
C:  0.6667  0.3333  0.6431 
C:  0.6667  0.3333  0.1787 
C:  0.0000  1.0000  0.7364 
O:  0.6780  0.1907  0.6393 
O:  0.5247  0.1786  0.1760 
O:  0.0045  0.1505  0.7434 
O:  0.3220  0.5127  0.3607 
O:  0.4753  0.6540  0.8240 
O:  0.9955  0.1460  0.2566 
O:  0.5127  0.3220  0.6393 
O:  0.6540  0.4753  0.1760 
O:  0.1460  0.9955  0.7434 
O:  0.8093  0.4873  0.6393 
O:  0.8214  0.3460  0.1760 
O:  0.8495  0.8540  0.7434 
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: 26
k-points  
   grid: 3 3 4 
   number of shifts: 
   shifts: 0 0 0 
Kinetic energy cut-off: 40 Ha  [=1088.464 eV ]
eXchange-Correlation functional: LDA pw90 

Pseudopotentials: 
Ba:  Tetter norm-conserving pseudopotential 
Ca:  calcium, fhi98PP : Trouiller-Martins-type, LDA Ceperley/Alder Perdew/Wang (1992), l= 0 local 
C:  carbon, 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