-    RINGWOODITE     -    Mg2SiO4

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:  227  Fd-3m 
Lattice parameters (Å):  8.0709  8.0709  8.0709 
Angles (°):  90.0  90.0  90.0 

Symmetry (theoretical): 

Space group:  227  Fd-3m 
Lattice parameters (Å):  5.6170  5.6170  5.6170 
Angles (°):  60.0  60.0  60.0 

Cell contents: 

Number of atoms:  14 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Si:  0.1250  0.1250  0.1250 
Si:  0.8750  0.8750  0.8750 
Mg:  0.5000  0.5000  0.5000 
Mg:  0.5000  0.5000  0.0000 
Mg:  0.5000  0.0000  0.5000 
Mg:  0.0000  0.5000  0.5000 
O:  0.2448  0.2448  0.2448 
O:  0.2448  0.2448  0.7657 
O:  0.2448  0.7657  0.2448 
O:  0.7657  0.2448  0.2448 
O:  0.7552  0.7552  0.2343 
O:  0.7552  0.7552  0.7552 
O:  0.7552  0.2343  0.7552 
O:  0.2343  0.7552  0.7552 
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
T1u
0
0
0
0
2
T1u
0
0
0
0
3
T1u
0
0
0
0
4
T2u
213
213
213
213
5
T2u
213
213
213
213
6
T2u
213
213
213
213
7
T2g
309
309
309
309
1.972e+37
0.1
2.712e+37
0.1
4.685e+37
0.1
8
T2g
309
309
309
309
2.053e+37
0.1
1.979e+37
0.1
4.032e+37
0.1
9
T2g
309
309
309
309
2.046e+37
0.1
3.358e+37
0.1
5.404e+37
0.1
10
T1g
350
350
350
350
11
T1g
350
350
350
350
12
T1g
350
350
350
350
13
T1u
351
351
351
351
14
T1u
351
351
351
351
15
T1u
351
351
351
351
16
Eu
357
357
357
357
17
Eu
357
357
357
357
18
Eg
377
377
377
377
9.782e+38
2.6
7.337e+38
1.9
1.712e+39
4.5
19
Eg
377
377
377
377
9.782e+38
2.6
7.337e+38
1.9
1.712e+39
4.5
20
T1u
419
419
419
419
21
T1u
419
419
419
419
22
T1u
419
450
450
450
23
T2u
450
450
450
450
24
T2u
450
450
450
450
25
T2u
450
542
542
542
26
T1u
547
547
547
547
27
T1u
547
547
547
547
28
T1u
547
554
554
554
29
Eu
554
554
554
554
30
Eu
554
560
560
560
31
A2u
581
581
581
581
32
T2g
594
594
594
594
6.062e+37
0.2
7.274e+37
0.2
1.334e+38
0.4
33
T2g
594
594
594
594
6.043e+37
0.2
9.014e+37
0.2
1.506e+38
0.4
34
T2g
594
594
594
594
6.062e+37
0.2
8.522e+37
0.2
1.458e+38
0.4
35
T2g
804
804
804
804
5.585e+39
14.8
9.411e+39
25.0
1.500e+40
39.8
36
T2g
804
804
804
804
5.585e+39
14.8
5.541e+39
14.7
1.113e+40
29.5
37
T2g
804
804
804
804
5.585e+39
14.8
8.087e+39
21.5
1.367e+40
36.3
38
A2u
813
813
813
813
39
T1u
816
816
816
816
40
T1u
816
816
816
816
41
T1u
816
829
829
829
42
A1g
829
975
975
975
3.766e+40
100.0
0.000e+0
0.0
3.766e+40
100.0
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.