-    CRISTOBALITE     -    SiO2

The crystal structure is fully relaxed (both unit cell parameters and atomic positions under symmetry constraints) at 40GPa 

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:  Theo Pc 
Lattice parameters (Å):  6.7500  4.0633  6.8344 
Angles (°):  90  90  90 

Symmetry (theoretical): 

Space group:  Theo Pc 
Lattice parameters (Å):  6.4326  3.8884  6.6717 
Angles (°):  90.00  98.05  90.00 

Cell contents: 

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

Atomic positions (theoretical):

Si:  0.4917  0.0021  0.5018 
Si:  0.9917  0.4979  0.0018 
Si:  0.3600  0.9956  0.1183 
Si:  0.1370  0.5021  0.3758 
Si:  0.6370  0.9979  0.8758 
Si:  0.8600  0.5044  0.6183 
Si:  0.2687  0.4956  0.7593 
Si:  0.7687  0.0044  0.2593 
O:  0.3298  0.2314  0.3318 
O:  0.1657  0.7326  0.1674 
O:  0.6657  0.7674  0.6674 
O:  0.8298  0.2686  0.8318 
O:  0.4630  0.2326  0.7102 
O:  0.0432  0.7189  0.7958 
O:  0.5432  0.7811  0.2958 
O:  0.9630  0.2674  0.2102 
O:  0.2989  0.7314  0.5458 
O:  0.2061  0.2511  0.9576 
O:  0.7061  0.2489  0.4576 
O:  0.7989  0.7686  0.0458 
O:  0.4226  0.7511  0.9200 
O:  0.0856  0.2811  0.5818 
O:  0.5856  0.2189  0.0818 
O:  0.9226  0.7489  0.4200 
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
0
0
0
0
2
0
0
0
0
3
0
0
0
0
4
281
281
281
281
5.565e+38
4.5
3.209e+37
0.3
5.886e+38
4.8
5
313
313
313
313
4.320e+37
0.4
3.285e+36
0.0
4.649e+37
0.4
6
349
350
349
349
7
354
354
354
354
5.250e+35
0.0
7.219e+35
0.0
1.247e+36
0.0
8
378
378
378
378
9
385
385
386
385
10
391
391
391
391
11
395
395
395
395
4.251e+38
3.5
9.476e+36
0.1
4.346e+38
3.5
12
417
418
417
424
13
426
426
427
426
14
428
428
428
428
1.121e+38
0.9
1.874e+38
1.5
2.996e+38
2.4
15
431
431
433
431
16
433
433
439
433
2.319e+38
1.9
2.599e+37
0.2
2.579e+38
2.1
17
478
479
478
479
18
491
491
491
491
1.992e+37
0.2
2.546e+37
0.2
4.537e+37
0.4
19
491
491
493
491
1.665e+38
1.4
2.128e+38
1.7
3.793e+38
3.1
20
493
493
504
493
6.959e+39
56.7
8.618e+37
0.7
7.045e+39
57.4
21
504
504
505
504
6.214e+38
5.1
7.098e+38
5.8
1.331e+39
10.9
22
514
517
514
516
23
530
530
530
530
3.079e+38
2.5
2.229e+38
1.8
5.307e+38
4.3
24
540
540
540
540
1.833e+38
1.5
2.173e+38
1.8
4.006e+38
3.3
25
561
561
561
561
3.296e+37
0.3
5.232e+37
0.4
8.528e+37
0.7
26
564
568
564
564
27
568
572
568
568
28
577
584
577
582
29
584
593
593
584
30
593
601
596
593
2.084e+39
17.0
2.527e+37
0.2
2.110e+39
17.2
31
601
612
612
601
32
612
615
621
612
5.454e+37
0.4
8.916e+37
0.7
1.437e+38
1.2
33
630
631
630
631
34
631
632
631
632
3.508e+39
28.6
1.318e+38
1.1
3.640e+39
29.7
35
632
636
633
635
36
636
648
636
636
3.287e+38
2.7
3.717e+38
3.0
7.004e+38
5.7
37
648
650
648
648
6.876e+39
56.1
1.469e+38
1.2
7.023e+39
57.3
38
650
653
650
650
3.488e+38
2.8
4.530e+38
3.7
8.018e+38
6.5
39
679
679
679
679
1.409e+38
1.1
1.504e+38
1.2
2.913e+38
2.4
40
681
681
681
681
6.444e+39
52.5
1.036e+38
0.8
6.548e+39
53.4
41
684
687
684
684
42
697
705
697
697
43
711
712
711
712
44
712
724
724
724
45
724
741
728
741
1.217e+40
99.2
9.926e+37
0.8
1.227e+40
100.0
46
741
744
741
754
1.011e+39
8.2
1.663e+39
13.6
2.674e+39
21.8
47
754
754
758
766
48
766
766
766
770
5.143e+38
4.2
1.837e+37
0.1
5.327e+38
4.3
49
770
770
770
772
1.729e+39
14.1
2.396e+36
0.0
1.732e+39
14.1
50
772
772
777
796
51
796
796
800
796
52
800
825
830
830
53
830
830
836
831
3.560e+38
2.9
5.934e+38
4.8
9.493e+38
7.7
54
836
838
838
838
55
838
841
841
839
1.881e+37
0.2
2.450e+37
0.2
4.331e+37
0.4
56
841
848
848
848
57
848
874
872
874
1.769e+39
14.4
3.634e+37
0.3
1.805e+39
14.7
58
874
881
880
879
59
881
901
881
881
1.843e+39
15.0
4.339e+37
0.4
1.886e+39
15.4
60
901
913
901
913
61
913
916
913
916
1.163e+38
0.9
1.674e+38
1.4
2.837e+38
2.3
62
916
936
916
952
2.432e+39
19.8
2.161e+36
0.0
2.434e+39
19.8
63
952
952
955
955
64
955
955
956
956
1.042e+40
84.9
3.252e+37
0.3
1.045e+40
85.2
65
956
956
974
973
5.183e+37
0.4
8.296e+37
0.7
1.348e+38
1.1
66
974
985
984
985
67
985
997
1013
1012
68
1013
1013
1013
1013
69
1013
1029
1029
1029
70
1029
1048
1048
1048
3.949e+38
3.2
2.835e+35
0.0
3.952e+38
3.2
71
1048
1105
1105
1105
1.995e+38
1.6
3.202e+38
2.6
5.197e+38
4.2
72
1105
1157
1142
1130
4.953e+38
4.0
7.780e+38
6.3
1.273e+39
10.4
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.