-    CASSITERITE     -    SnO2

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:  136  P4_2/mnm 
Lattice parameters (Å):  4.7300  4.7300  3.1800 
Angles (°):  90.0  90.0  90.0 

Symmetry (theoretical): 

Space group:  136  P4_2/mnm 
Lattice parameters (Å):  4.8082  4.8082  3.2651 
Angles (°):  90.0  90.0  90.0 

Cell contents: 

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

Atomic positions (theoretical):

Sn:  0.0000  0.0000  0.0000 
Sn:  0.5000  0.5000  0.5000 
O:  0.3067  0.3067  0.0000 
O:  0.1933  0.8067  0.5000 
O:  0.6933  0.6933  0.0000 
O:  0.8067  0.1933  0.5000 
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
B1g
77
77
77
77
5.068e+39
1.2
3.801e+39
0.9
8.869e+39
2.0
5
B1u
134
134
134
134
6
E1u
192
192
192
192
7
E1u
192
245
245
192
8
E1u
267
267
267
267
9
E1u
267
297
297
267
10
A2g
315
315
315
315
11
A2u
446
446
446
453
12
E1g
453
453
453
453
3.975e+39
0.9
4.224e+39
1.0
8.199e+39
1.9
13
E1g
453
453
453
539
3.975e+39
0.9
6.708e+39
1.5
1.068e+40
2.5
14
B1u
539
539
539
573
15
E1u
573
573
573
573
16
E1u
573
608
608
608
17
A1g
608
698
698
638
4.283e+41
98.8
5.253e+39
1.2
4.335e+41
100.0
18
B2g
726
726
726
726
5.361e+40
12.4
7.371e+40
17.0
1.273e+41
29.4
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.