-    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):  4.6339  4.6339  15.0177 
Angles (°):  90  90  120 

Symmetry (theoretical): 

Space group:  167  R-3c 
Lattice parameters (Å):  5.6637  5.6637  5.6637 
Angles (°):  48.38  48.38  48.38 

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:  0.5257  0.9743  0.2500 
O:  0.9743  0.2500  0.5257 
Mg:  0.5000  0.5000  0.5000 
C:  0.7500  0.7500  0.7500 
O:  0.7500  0.4743  0.0257 
O:  0.2500  0.5257  0.9743 
O:  0.4743  0.0257  0.7500 
O:  0.0257  0.7500  0.4743 
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
Eg
204
204
204
204
6.156e+38
0.7
7.524e+38
0.8
1.368e+39
1.5
5
Eg
204
204
204
204
6.156e+38
0.7
1.006e+39
1.1
1.621e+39
1.7
6
Eu
227
227
227
227
7
Eu
227
230
230
227
8
A2u
230
235
235
271
9
A2g
292
292
292
292
10
Eu
292
292
292
292
11
Eu
292
296
296
292
12
Eg
314
314
314
314
8.936e+39
9.6
1.399e+40
15.0
2.293e+40
24.6
13
Eg
314
314
314
314
8.936e+39
9.6
1.108e+40
11.9
2.002e+40
21.5
14
A2g
342
342
342
342
15
Eu
342
342
342
342
16
Eu
342
347
347
342
17
A2u
347
358
358
358
18
A1u
358
462
462
445
19
Eg
720
720
720
720
3.024e+39
3.2
3.017e+39
3.2
6.041e+39
6.5
20
Eg
720
720
720
720
3.024e+39
3.2
3.916e+39
4.2
6.940e+39
7.4
21
Eu
726
726
726
726
22
Eu
726
729
729
726
23
A2u
848
848
848
857
24
A2g
857
857
857
877
25
A1g
1087
1087
1087
1087
9.058e+40
97.2
2.593e+39
2.8
9.317e+40
100.0
26
A1u
1089
1089
1089
1089
27
Eu
1422
1422
1422
1422
28
Eu
1422
1440
1440
1422
29
Eg
1440
1440
1440
1440
1.336e+39
1.4
1.849e+39
2.0
3.185e+39
3.4
30
Eg
1440
1583
1583
1440
1.336e+39
1.4
1.053e+39
1.1
2.390e+39
2.6
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.