-    MAGNESITE     -    MgCO3

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:  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):  5.5291  5.5291  5.5291 
Angles (°):  49.01  49.01  49.01 

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:  0.5280  0.9720  0.2500 
O:  0.9720  0.2500  0.5280 
Mg:  0.5000  0.5000  0.5000 
C:  0.7500  0.7500  0.7500 
O:  0.7500  0.4720  0.0280 
O:  0.2500  0.5280  0.9720 
O:  0.4720  0.0280  0.7500 
O:  0.0280  0.7500  0.4720 
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
226
226
226
226
8.377e+38
0.9
1.119e+39
1.1
1.956e+39
2.0
5
Eg
226
226
226
226
8.377e+38
0.9
1.293e+39
1.3
2.131e+39
2.2
6
Eu
228
228
228
228
7
Eu
228
234
234
228
8
A2u
234
240
240
279
9
A2g
313
313
313
313
10
Eu
327
327
327
327
11
Eu
327
334
334
327
12
Eg
345
345
345
345
7.679e+39
7.9
1.256e+40
12.9
2.024e+40
20.7
13
Eg
345
345
345
345
7.679e+39
7.9
9.107e+39
9.3
1.679e+40
17.2
14
A2g
377
377
377
377
15
A1u
383
383
383
383
16
Eu
391
391
391
391
17
Eu
391
401
401
391
18
A2u
401
496
496
483
19
Eg
733
733
733
733
3.482e+39
3.6
3.158e+39
3.2
6.640e+39
6.8
20
Eg
733
733
733
733
3.482e+39
3.6
4.807e+39
4.9
8.289e+39
8.5
21
Eu
741
741
741
741
22
Eu
741
746
746
741
23
A2u
847
847
847
856
24
A2g
856
856
856
881
25
A1g
1105
1105
1105
1105
9.501e+40
97.3
2.614e+39
2.7
9.763e+40
100.0
26
A1u
1107
1107
1107
1107
27
Eu
1448
1448
1448
1448
28
Eu
1448
1467
1467
1448
29
Eg
1467
1467
1467
1467
1.043e+39
1.1
1.132e+39
1.2
2.175e+39
2.2
30
Eg
1467
1612
1612
1467
1.043e+39
1.1
1.206e+39
1.2
2.249e+39
2.3
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.