-    MAGNESITE     -    MgCO3

Theoretical atomic positions and lattice parameters at experimental volum from 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:  167  R-3c 
Lattice parameters (Å):  4.6330  4.6330  15.0200 
Angles (°):  90  90  120 

Symmetry (theoretical): 

Space group:  167  R-3c 
Lattice parameters (Å):  5.6667  5.6667  5.6667 
Angles (°):  49.03  49.03  49.03 

Cell contents: 

Number of atoms:  10 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Mg:  0.0000  0.0000  0.0000 
C:  0.2500  0.2500  0.2500 
O:  0.5260  0.9740  0.2500 
O:  0.9740  0.2500  0.5260 
Mg:  0.5000  0.5000  0.5000 
C:  0.7500  0.7500  0.7500 
O:  0.7500  0.4740  0.0260 
O:  0.2500  0.5260  0.9740 
O:  0.4740  0.0260  0.7500 
O:  0.0260  0.7500  0.4740 
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.
     

Powder Raman 

Powder Raman spectrum

The intensity of the Raman peaks is computed within the density-functional perturbation theory. The intensity depends on the temperature (for now fixed at 300K), frequency of the input laser (for now fixed at 21834 cm-1, frequency of the phonon mode and the Raman tensor. The Raman tensor represents the derivative of the dielectric tensor during the atomic displacement that corresponds to the phonon vibration. The Raman tensor is related to the polarizability of a specific phonon mode.

Horizontal:
Xmin:
Xmax:
Vertical:
Ymin:
Ymax:
 
Choose the polarization of the lasers.
I ∥ 
I ⊥ 
I Total 

Data about the phonon modes

Frequency of the transverse (TO) and longitudinal (LO) phonon modes in the zone-center. The longitudinal modes are computed along the three cartesian directions. You can visualize the atomic displacement pattern corresponding to each phonon by clicking on the appropriate cell in the table below.

1
ac
0
0
0
0
2
ac
0
0
0
0
3
ac
0
0
0
0
4
A2u
202
202
202
202
5.370e+38
0.6
6.490e+38
0.7
1.186e+39
1.3
5
Eu
202
202
202
202
5.370e+38
0.6
8.748e+38
0.9
1.412e+39
1.5
6
Eu
229
229
229
229
7
Eg
229
232
232
229
8
Eg
232
237
237
273
9
A2g
287
287
287
287
10
Eu
287
290
290
287
11
Eu
293
293
293
293
12
Eg
312
312
312
312
9.122e+39
9.7
1.423e+40
15.2
2.335e+40
24.9
13
Eg
312
312
312
312
9.122e+39
9.7
1.135e+40
12.1
2.047e+40
21.9
14
A1u
335
335
335
335
15
A2g
335
339
339
335
16
Eu
339
339
339
339
17
Eu
339
355
355
355
18
A2u
355
459
459
440
19
Eg
719
719
719
719
3.057e+39
3.3
3.773e+39
4.0
6.830e+39
7.3
20
Eg
719
719
719
719
3.057e+39
3.3
3.244e+39
3.5
6.302e+39
6.7
21
Eu
725
725
725
725
22
Eu
725
728
728
725
23
A2u
848
848
848
857
24
A2g
857
857
857
877
25
A1g
1085
1085
1085
1085
9.106e+40
97.2
2.607e+39
2.8
9.367e+40
100.0
26
A1u
1087
1087
1087
1087
27
Eu
1419
1419
1419
1419
28
Eu
1419
1436
1436
1419
29
Eg
1436
1436
1436
1436
1.341e+39
1.4
1.882e+39
2.0
3.223e+39
3.4
30
Eg
1436
1580
1580
1436
1.341e+39
1.4
1.008e+39
1.1
2.349e+39
2.5
No.  Char.  ω TO  ω LOx  ω LOy  ω LOz  I ∥  I ⊥  I Total 
You can define the size of the supercell for the visualization of the vibration.
Nx: 
Ny: 
Nz: 
Normalized
Raw
Options for intensity.