-    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):  6.8844  6.8844  6.9760 
Angles (°):  75.32  104.67  58.81 

Cell contents: 

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

Atomic positions (theoretical):

Si:  0.2451  0.9802  0.0666 
Si:  0.6658  0.6466  0.5480 
O:  0.0000  0.0000  1.0000 
O:  0.6021  0.6021  0.7500 
O:  0.3764  0.8975  0.9141 
O:  0.4251  0.7724  0.3223 
O:  0.2508  0.1742  0.4657 
Si:  0.9802  0.2451  0.4334 
Si:  0.6466  0.6658  0.9520 
O:  0.0000  0.0000  0.5000 
O:  0.8975  0.3764  0.5859 
O:  0.7724  0.4251  0.1777 
O:  0.1742  0.2508  0.0343 
Si:  0.7549  0.0198  0.9334 
Si:  0.3342  0.3534  0.4520 
O:  0.3979  0.3979  0.2500 
O:  0.6236  0.1025  0.0859 
O:  0.5749  0.2276  0.6777 
O:  0.7492  0.8258  0.5343 
Si:  0.0198  0.7549  0.5666 
Si:  0.3534  0.3342  0.0480 
O:  0.1025  0.6236  0.4141 
O:  0.2276  0.5749  0.8223 
O:  0.8258  0.7492  0.9657 
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
77
77
77
77
1.339e+39
1.5
1.515e+39
1.7
2.854e+39
3.2
5
Au
115
115
115
115
6
Bu
124
124
124
124
7
Bg
158
158
158
158
9.604e+38
1.1
1.604e+39
1.8
2.564e+39
2.8
8
Au
161
161
161
161
9
Ag
179
179
179
179
3.329e+39
3.7
1.281e+39
1.4
4.610e+39
5.1
10
Au
186
186
186
186
11
Bg
198
198
198
198
1.997e+38
0.2
2.746e+38
0.3
4.744e+38
0.5
12
Bu
202
203
202
202
13
Ag
216
216
216
216
2.043e+39
2.3
1.546e+39
1.7
3.589e+39
4.0
14
Ag
234
234
234
234
3.038e+39
3.4
1.241e+39
1.4
4.279e+39
4.7
15
Bg
237
237
237
237
5.966e+38
0.7
1.005e+39
1.1
1.602e+39
1.8
16
Au
247
247
247
247
17
Bu
248
249
248
248
18
Ag
272
272
272
272
1.658e+40
18.4
1.010e+38
0.1
1.668e+40
18.5
19
Bg
277
277
277
277
9.401e+37
0.1
1.521e+38
0.2
2.461e+38
0.3
20
Bu
279
279
279
280
21
Au
280
280
287
280
22
Bu
294
294
294
294
23
Bg
311
311
311
311
2.125e+38
0.2
3.468e+38
0.4
5.592e+38
0.6
24
Au
319
319
321
319
25
Ag
329
329
329
329
3.979e+39
4.4
7.979e+38
0.9
4.777e+39
5.3
26
Bu
342
346
342
346
27
Ag
346
346
346
353
3.114e+39
3.5
1.303e+39
1.4
4.418e+39
4.9
28
Au
362
362
363
362
29
Bu
363
364
364
364
30
Bg
364
377
375
370
7.177e+38
0.8
7.629e+38
0.8
1.481e+39
1.6
31
Bu
377
396
377
379
32
Au
417
417
417
417
33
Bu
417
418
422
422
34
Ag
422
422
427
431
6.242e+39
6.9
9.548e+38
1.1
7.197e+39
8.0
35
Bu
431
441
431
441
36
Bg
441
454
441
454
5.222e+38
0.6
8.685e+38
1.0
1.391e+39
1.5
37
Bg
454
455
454
455
1.980e+37
0.0
2.722e+37
0.0
4.702e+37
0.1
38
Au
455
457
460
460
3.817e+37
0.0
5.249e+37
0.1
9.066e+37
0.1
39
Ag
460
460
478
475
2.243e+39
2.5
5.997e+38
0.7
2.842e+39
3.1
40
Au
495
495
499
495
41
Ag
541
541
541
541
8.998e+40
99.7
2.843e+38
0.3
9.026e+40
100.0
42
Bg
564
564
564
564
8.393e+37
0.1
1.403e+38
0.2
2.242e+38
0.2
43
Au
574
574
606
574
44
Bu
614
638
614
615
45
Bg
671
671
671
671
9.847e+36
0.0
1.611e+37
0.0
2.596e+37
0.0
46
Bu
697
700
697
700
47
Au
700
703
700
703
48
Ag
703
707
703
728
2.028e+39
2.2
2.761e+37
0.0
2.055e+39
2.3
49
Bg
813
813
813
813
6.919e+37
0.1
7.973e+37
0.1
1.489e+38
0.2
50
Bu
817
819
817
818
51
Ag
819
828
819
819
1.689e+39
1.9
6.240e+38
0.7
2.313e+39
2.6
52
Au
845
845
851
845
53
Bg
855
855
855
855
3.540e+37
0.0
5.946e+37
0.1
9.486e+37
0.1
54
Ag
858
858
858
858
1.766e+39
2.0
6.282e+38
0.7
2.395e+39
2.7
55
Au
882
882
883
882
56
Ag
888
888
888
888
7.625e+38
0.8
6.245e+38
0.7
1.387e+39
1.5
57
Bu
1052
1056
1052
1052
58
Ag
1060
1060
1060
1060
6.927e+38
0.8
5.570e+38
0.6
1.250e+39
1.4
59
Bg
1061
1061
1061
1061
3.285e+38
0.4
4.340e+38
0.5
7.625e+38
0.8
60
Au
1085
1085
1096
1085
61
Bu
1096
1103
1103
1103
62
Bg
1103
1110
1110
1106
3.041e+38
0.3
5.016e+38
0.6
8.057e+38
0.9
63
Au
1110
1114
1114
1110
64
Ag
1114
1129
1140
1114
4.019e+38
0.4
4.834e+38
0.5
8.853e+38
1.0
65
Bu
1140
1161
1161
1161
66
Bg
1161
1179
1170
1167
7.338e+38
0.8
8.468e+38
0.9
1.581e+39
1.8
67
Bu
1180
1184
1180
1184
68
Au
1184
1190
1190
1190
69
Ag
1190
1213
1213
1213
4.142e+38
0.5
4.338e+38
0.5
8.479e+38
0.9
70
Bg
1213
1252
1214
1304
3.620e+38
0.4
3.848e+38
0.4
7.468e+38
0.8
71
Bu
1308
1319
1308
1309
72
Au
1319
1320
1367
1319
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.