-    SPINEL     -    MgAl2O4

The crystal structure is fully relaxed (both unit cell parameters and atomic positions under symmetry constraints) starting from an experimental structure similar to the one reported in AMCSD 

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:  227  Fd-3m 
Lattice parameters (Å):  8.09580  8.09580  8.09580 
Angles (°):  90.0  90.0  90.0 

Symmetry (theoretical): 

Space group:  227  Fd-3m 
Lattice parameters (Å):  5.6076  5.6076  5.6076 
Angles (°):  60.0  60.0  60.0 

Cell contents: 

Number of atoms:  14 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Mg:  0.1250  0.1250  0.1250 
Mg:  0.8750  0.8750  0.8750 
Al:  0.5000  0.5000  0.5000 
Al:  0.5000  0.5000  0.0000 
Al:  0.5000  0.0000  0.5000 
Al:  0.0000  0.5000  0.5000 
O:  0.2630  0.2630  0.2630 
O:  0.2630  0.2630  0.7110 
O:  0.2630  0.7110  0.2630 
O:  0.7110  0.2630  0.2630 
O:  0.7370  0.7370  0.2890 
O:  0.7370  0.7370  0.7370 
O:  0.7370  0.2890  0.7370 
O:  0.2890  0.7370  0.7370 
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
T1u
262
262
262
262
5
T1u
262
262
262
262
6
T1u
262
262
262
262
7
T2u
314
314
314
314
8
T2u
314
314
314
314
9
T2u
314
316
316
316
10
T1g
316
316
316
316
1.071e+38
0.8
1.414e+38
1.0
2.485e+38
1.8
11
T1g
316
316
316
316
1.070e+38
0.8
1.138e+38
0.8
2.208e+38
1.6
12
T1g
316
317
317
317
1.072e+38
0.8
1.808e+38
1.3
2.880e+38
2.0
13
T2g
347
347
347
347
14
T2g
347
347
347
347
15
T2g
347
347
347
347
16
E1u
397
397
397
397
17
E1u
397
397
397
397
18
E1g
409
409
409
409
8.111e+39
57.1
6.083e+39
42.9
1.419e+40
100.0
19
E1g
409
409
409
409
8.111e+39
57.1
6.083e+39
42.9
1.419e+40
100.0
20
T1u
463
463
463
463
21
T1u
463
463
463
463
22
T1u
463
463
463
463
23
T2u
481
481
481
481
24
T2u
481
481
481
481
25
T2u
481
569
569
569
26
T1g
569
569
569
569
7.417e+36
0.1
8.521e+36
0.1
1.594e+37
0.1
27
T1g
569
569
569
569
7.422e+36
0.1
1.204e+37
0.1
1.947e+37
0.1
28
T1g
569
584
584
584
7.423e+36
0.1
1.014e+37
0.1
1.756e+37
0.1
29
T2u
587
587
587
587
30
T2u
587
587
587
587
31
T2u
587
606
606
606
32
E1u
606
606
606
606
33
E1u
606
625
625
625
34
B1u
662
662
662
662
35
T1g
678
678
678
678
2.088e+39
14.7
2.722e+39
19.2
4.810e+39
33.9
36
T1g
678
678
678
678
2.088e+39
14.7
3.286e+39
23.2
5.374e+39
37.9
37
T1g
678
678
678
678
2.088e+39
14.7
2.603e+39
18.3
4.691e+39
33.1
38
T2u
685
685
685
685
39
T2u
685
685
685
685
40
T2u
685
758
758
758
41
B1u
758
771
771
771
42
A1g
771
857
857
857
2.181e+39
15.4
4.586e+26
0.0
2.181e+39
15.4
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.