-    QUARTZ     -    SiO2

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

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:  154  P3_221 
Lattice parameters (Å):       
Angles (°):  90.0  90.0  120.0 

Symmetry (theoretical): 

Space group:  154  P3_221 
Lattice parameters (Å):  4.9134  4.9134  5.4042 
Angles (°):  90.0  90.0  120.0 

Cell contents: 

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

Atomic positions (theoretical):

Si:  0.4727  0.0000  0.1667 
Si:  0.0000  0.4727  0.8333 
Si:  0.5273  0.5273  0.5000 
O:  0.4151  0.2623  0.2904 
O:  0.7377  0.1528  0.9570 
O:  0.8472  0.5849  0.6237 
O:  0.2623  0.4151  0.7096 
O:  0.1528  0.7377  0.0430 
O:  0.5849  0.8472  0.3763 
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
E
120
120
120
120
1.661e+39
2.6
1.718e+39
2.7
3.379e+39
5.4
5
E
120
120
120
120
1.661e+39
2.6
2.801e+39
4.4
4.462e+39
7.1
6
A1
182
182
182
182
3.097e+40
49.1
1.905e+37
0.0
3.099e+40
49.2
7
E
252
252
252
252
3.860e+38
0.6
5.120e+38
0.8
8.980e+38
1.4
8
E
252
253
253
252
3.860e+38
0.6
4.661e+38
0.7
8.521e+38
1.4
9
A1
345
345
345
345
1.726e+39
2.7
6.950e+38
1.1
2.421e+39
3.8
10
A2
358
358
358
380
11
E
382
382
382
382
4.156e+38
0.7
3.217e+38
0.5
7.374e+38
1.2
12
E
382
391
391
382
4.156e+38
0.7
6.214e+38
1.0
1.037e+39
1.6
13
E
433
433
433
433
3.711e+38
0.6
4.990e+38
0.8
8.701e+38
1.4
14
E
433
445
445
433
3.711e+38
0.6
5.601e+38
0.9
9.312e+38
1.5
15
A1
445
474
474
445
6.302e+40
100.0
1.779e+35
0.0
6.302e+40
100.0
16
A2
474
492
492
532
17
E
680
680
680
680
3.175e+38
0.5
3.025e+38
0.5
6.199e+38
1.0
18
E
680
682
682
680
3.175e+38
0.5
5.294e+38
0.8
8.469e+38
1.3
19
A2
766
766
766
776
20
E
780
780
780
780
4.695e+38
0.7
6.184e+38
1.0
1.088e+39
1.7
21
E
780
793
793
780
4.695e+38
0.7
5.605e+38
0.9
1.030e+39
1.6
22
E
1063
1063
1063
1063
3.162e+38
0.5
4.183e+38
0.7
7.345e+38
1.2
23
E
1063
1070
1070
1063
3.162e+38
0.5
3.801e+38
0.6
6.963e+38
1.1
24
A2
1070
1078
1078
1078
25
A1
1078
1152
1152
1155
3.455e+38
0.5
2.391e+38
0.4
5.846e+38
0.9
26
E
1155
1155
1155
1155
6.575e+38
1.0
5.617e+38
0.9
1.219e+39
1.9
27
E
1155
1225
1225
1234
6.575e+38
1.0
1.057e+39
1.7
1.715e+39
2.7
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.