-    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):  1.0000  1.0000  1.0000 
Angles (°):  rprim  4.9862233303E-01  8.6681875122E-01 

Symmetry (theoretical): 

Space group:  15  C2/c 
Lattice parameters (Å):  7.0695  7.0695  7.1148 
Angles (°):  75.36  104.63  59.81 

Cell contents: 

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

Atomic positions (theoretical):

Si:  0.2481  0.9699  0.0717 
Si:  0.6650  0.6503  0.5421 
O:  0.0000  0.0000  0.0000 
O:  0.6141  0.6141  0.7500 
O:  0.3876  0.8634  0.9364 
O:  0.4166  0.7889  0.3272 
O:  0.2324  0.1914  0.4753 
Si:  0.9699  0.2481  0.4283 
Si:  0.6503  0.6650  0.9579 
O:  0.0000  0.0000  0.5000 
O:  0.8634  0.3876  0.5636 
O:  0.7889  0.4166  0.1728 
O:  0.1914  0.2324  0.0247 
Si:  0.7519  0.0301  0.9283 
Si:  0.3350  0.3497  0.4579 
O:  0.3859  0.3859  0.2500 
O:  0.6124  0.1366  0.0636 
O:  0.5834  0.2111  0.6728 
O:  0.7676  0.8086  0.5247 
Si:  0.0301  0.7519  0.5717 
Si:  0.3497  0.3350  0.0421 
O:  0.1366  0.6124  0.4364 
O:  0.2111  0.5834  0.8272 
O:  0.8086  0.7676  0.9753 
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
Bg
77
77
77
77
9.307e+38
1.4
9.977e+38
1.5
1.928e+39
2.9
5
Au
111
111
111
111
6
Ag
125
125
125
125
6.890e+39
10.5
1.034e+39
1.6
7.924e+39
12.1
7
Bu
137
137
137
137
8
Bg
144
144
144
144
1.218e+39
1.9
2.055e+39
3.1
3.273e+39
5.0
9
Au
145
145
145
145
10
Ag
177
177
177
177
7.138e+39
10.9
1.624e+39
2.5
8.762e+39
13.4
11
Au
179
179
179
179
12
Bg
192
192
192
192
1.279e+38
0.2
1.865e+38
0.3
3.144e+38
0.5
13
Ag
198
198
198
198
1.986e+39
3.0
1.575e+39
2.4
3.561e+39
5.4
14
Bg
235
235
235
235
1.242e+38
0.2
1.566e+38
0.2
2.808e+38
0.4
15
Bu
244
244
244
244
16
Au
254
254
255
254
17
Ag
262
262
262
262
1.262e+40
19.3
2.564e+38
0.4
1.288e+40
19.6
18
Bu
264
264
264
264
19
Bg
280
280
280
280
5.673e+36
0.0
6.339e+36
0.0
1.201e+37
0.0
20
Au
283
283
286
283
21
Bu
286
286
287
286
22
Bu
292
292
292
292
23
Bg
305
305
305
305
1.894e+38
0.3
3.137e+38
0.5
5.031e+38
0.8
24
Ag
318
318
318
318
1.978e+39
3.0
5.625e+38
0.9
2.541e+39
3.9
25
Au
318
318
319
318
26
Bu
330
332
330
337
27
Ag
344
344
344
344
8.639e+38
1.3
7.161e+38
1.1
1.580e+39
2.4
28
Bu
361
365
361
361
29
Au
365
369
369
365
30
Bg
369
371
377
369
2.040e+38
0.3
2.219e+38
0.3
4.259e+38
0.6
31
Bu
381
390
381
381
32
Au
407
407
407
407
33
Bu
407
411
414
414
34
Ag
414
414
414
425
4.039e+39
6.2
5.316e+38
0.8
4.570e+39
7.0
35
Bu
428
430
428
430
36
Bg
430
441
430
441
1.870e+38
0.3
3.120e+38
0.5
4.989e+38
0.8
37
Au
441
448
448
448
38
Bg
448
455
455
455
1.634e+37
0.0
2.010e+37
0.0
3.643e+37
0.1
39
Ag
455
459
460
475
1.737e+39
2.6
3.071e+38
0.5
2.044e+39
3.1
40
Au
477
477
482
477
41
Ag
509
509
509
509
6.543e+40
99.8
1.180e+38
0.2
6.555e+40
100.0
42
Bg
529
529
529
529
5.711e+37
0.1
8.686e+37
0.1
1.440e+38
0.2
43
Au
538
538
577
538
44
Bu
584
616
584
584
45
Bg
647
647
647
647
2.961e+37
0.0
3.832e+37
0.1
6.793e+37
0.1
46
Ag
658
658
658
658
7.160e+38
1.1
3.997e+37
0.1
7.560e+38
1.2
47
Au
661
661
663
661
48
Bu
669
674
669
693
49
Bg
777
777
777
777
1.001e+38
0.2
1.099e+38
0.2
2.100e+38
0.3
50
Ag
780
780
780
780
8.590e+38
1.3
7.174e+38
1.1
1.576e+39
2.4
51
Bu
787
790
787
789
52
Au
806
806
809
806
53
Ag
809
809
809
809
1.272e+39
1.9
6.369e+38
1.0
1.909e+39
2.9
54
Bg
814
814
814
814
1.407e+37
0.0
2.342e+37
0.0
3.749e+37
0.1
55
Au
831
831
831
831
56
Ag
831
831
832
831
5.071e+38
0.8
4.387e+38
0.7
9.458e+38
1.4
57
Bu
1033
1034
1033
1033
58
Ag
1034
1037
1034
1034
6.202e+38
0.9
5.311e+38
0.8
1.151e+39
1.8
59
Bg
1037
1038
1037
1037
1.180e+38
0.2
1.426e+38
0.2
2.606e+38
0.4
60
Bu
1063
1064
1063
1064
61
Au
1064
1065
1065
1065
62
Bg
1065
1069
1069
1069
2.580e+38
0.4
4.333e+38
0.7
6.913e+38
1.1
63
Au
1069
1070
1070
1070
64
Ag
1070
1078
1089
1075
1.393e+38
0.2
1.529e+38
0.2
2.922e+38
0.4
65
Bu
1089
1138
1138
1138
66
Bg
1138
1140
1138
1140
8.829e+38
1.3
9.410e+38
1.4
1.824e+39
2.8
67
Au
1140
1148
1148
1144
68
Bu
1148
1155
1155
1155
69
Ag
1155
1171
1171
1171
6.238e+38
1.0
6.676e+38
1.0
1.291e+39
2.0
70
Bg
1171
1212
1191
1214
1.180e+38
0.2
1.401e+38
0.2
2.582e+38
0.4
71
Bu
1214
1225
1214
1225
72
Au
1225
1239
1266
1250
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.