-    COESITE     -    SiO2

 

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:  15  C2/c 
Lattice parameters (Å):       
Angles (°):       

Symmetry (theoretical): 

Space group:  15  C2/c 
Lattice parameters (Å):  6.7498  6.7498  6.8605 
Angles (°):  75.35  104.64  58.33 

Cell contents: 

Number of atoms:  24 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Si:  0.2440  0.9855  0.0631 
Si:  0.6642  0.6467  0.5502 
O:  0.0000  0.0000  1.0000 
O:  0.5953  0.5953  0.7500 
O:  0.3723  0.9133  0.9028 
O:  0.4286  0.7650  0.3194 
O:  0.2615  0.1636  0.4631 
Si:  0.9855  0.2440  0.4369 
Si:  0.6467  0.6642  0.9498 
O:  0.0000  0.0000  0.5000 
O:  0.9133  0.3723  0.5972 
O:  0.7650  0.4286  0.1806 
O:  0.1636  0.2615  0.0369 
Si:  0.7560  0.0145  0.9369 
Si:  0.3358  0.3533  0.4498 
O:  0.4047  0.4047  0.2500 
O:  0.6277  0.0867  0.0972 
O:  0.5714  0.2350  0.6806 
O:  0.7385  0.8364  0.5369 
Si:  0.0145  0.7560  0.5631 
Si:  0.3533  0.3358  0.0502 
O:  0.0867  0.6277  0.4028 
O:  0.2350  0.5714  0.8194 
O:  0.8364  0.7385  0.9631 
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
u
0
0
0
0
2
u
0
0
0
0
3
u
0
0
0
0
4
Bg
56
56
56
56
2.232e+39
2.1
2.610e+39
2.4
4.842e+39
4.5
5
Au
78
78
80
78
6
Bu
105
105
105
105
7
Bu
170
173
170
170
8
Au
174
174
174
174
9
Bg
178
178
178
178
5.572e+38
0.5
9.268e+38
0.9
1.484e+39
1.4
10
Bg
201
201
201
201
1.337e+38
0.1
1.652e+38
0.2
2.988e+38
0.3
11
Au
206
206
206
206
12
Ag
209
209
209
209
2.298e+39
2.1
1.231e+39
1.1
3.529e+39
3.2
13
Bu
224
227
224
225
14
Ag
231
231
231
231
1.799e+39
1.7
1.356e+39
1.2
3.155e+39
2.9
15
Bg
236
236
236
236
1.629e+39
1.5
2.714e+39
2.5
4.343e+39
4.0
16
Au
239
239
239
239
17
Ag
250
250
250
250
1.461e+39
1.3
8.819e+38
0.8
2.343e+39
2.2
18
Bg
273
273
273
273
8.149e+37
0.1
1.327e+38
0.1
2.142e+38
0.2
19
Bu
283
283
283
283
20
Au
285
285
293
285
21
Bu
296
297
296
296
22
Ag
297
297
297
297
1.095e+40
10.1
3.625e+38
0.3
1.131e+40
10.4
23
Bg
319
319
319
319
8.863e+37
0.1
1.456e+38
0.1
2.342e+38
0.2
24
Au
326
326
328
326
25
Ag
342
342
342
342
2.903e+39
2.7
7.726e+38
0.7
3.676e+39
3.4
26
Bu
344
348
344
354
27
Ag
355
355
355
355
8.644e+39
8.0
1.800e+39
1.7
1.044e+40
9.6
28
Au
358
358
359
358
29
Bu
359
363
363
363
30
Bg
363
383
376
380
1.220e+39
1.1
1.297e+39
1.2
2.517e+39
2.3
31
Bu
384
400
384
384
32
Bu
421
422
421
425
33
Au
425
425
432
432
34
Ag
432
432
433
432
7.675e+39
7.1
1.406e+39
1.3
9.081e+39
8.4
35
Bu
433
449
439
449
36
Bg
449
458
449
462
8.337e+38
0.8
1.373e+39
1.3
2.206e+39
2.0
37
Bg
462
462
462
467
7.068e+37
0.1
8.833e+37
0.1
1.590e+38
0.1
38
Au
467
467
467
467
3.513e+38
0.3
1.235e+38
0.1
4.747e+38
0.4
39
Ag
467
467
490
478
2.421e+39
2.2
8.524e+38
0.8
3.273e+39
3.0
40
Au
511
511
514
511
41
Ag
571
571
571
571
1.082e+41
99.6
4.226e+38
0.4
1.086e+41
100.0
42
Bg
592
592
592
592
1.047e+38
0.1
1.767e+38
0.2
2.814e+38
0.3
43
Au
602
602
628
602
44
Bu
640
658
640
641
45
Bg
691
691
691
691
2.504e+37
0.0
3.021e+37
0.0
5.525e+37
0.1
46
Bu
720
730
720
730
47
Au
730
734
730
734
48
Ag
734
734
734
756
3.323e+39
3.1
4.830e+37
0.0
3.371e+39
3.1
49
Bg
840
840
840
840
7.724e+37
0.1
9.214e+37
0.1
1.694e+38
0.2
50
Bu
843
851
843
843
51
Ag
851
860
851
851
2.593e+39
2.4
4.780e+38
0.4
3.071e+39
2.8
52
Au
878
878
885
878
53
Bg
888
888
888
888
5.447e+37
0.1
9.141e+37
0.1
1.459e+38
0.1
54
Ag
895
895
895
895
2.190e+39
2.0
6.234e+38
0.6
2.813e+39
2.6
55
Au
922
922
925
922
56
Ag
932
932
932
932
1.161e+39
1.1
8.560e+38
0.8
2.017e+39
1.9
57
Bu
1072
1074
1072
1072
58
Bg
1087
1087
1087
1087
7.211e+38
0.7
7.702e+38
0.7
1.491e+39
1.4
59
Ag
1087
1087
1087
1087
5.980e+38
0.6
5.791e+38
0.5
1.177e+39
1.1
60
Au
1105
1105
1120
1105
61
Bu
1120
1131
1131
1130
62
Bg
1131
1138
1138
1131
3.619e+38
0.3
5.531e+38
0.5
9.150e+38
0.8
63
Au
1138
1142
1142
1138
64
Ag
1142
1166
1174
1142
6.339e+38
0.6
7.562e+38
0.7
1.390e+39
1.3
65
Bu
1174
1185
1185
1185
66
Bg
1185
1207
1195
1190
6.769e+38
0.6
8.739e+38
0.8
1.551e+39
1.4
67
Bu
1214
1224
1214
1224
68
Au
1224
1228
1228
1228
69
Ag
1228
1251
1245
1251
2.818e+38
0.3
2.716e+38
0.3
5.533e+38
0.5
70
Bg
1251
1277
1251
1346
5.175e+38
0.5
5.555e+38
0.5
1.073e+39
1.0
71
Bu
1377
1388
1377
1377
72
Au
1388
1388
1438
1388
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.