-    FORSTERITE     -    Mg2SiO4

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:  62  Pbnm 
Lattice parameters (Å):  4.7503  10.1870  5.9771 
Angles (°):  90  90  90 

Symmetry (theoretical): 

Space group:  62  Pbnm 
Lattice parameters (Å):  4.6846  10.0026  5.8725 
Angles (°):  90  90  90 

Cell contents: 

Number of atoms:  28 
Number of atom types: 
Chemical composition: 

Atomic positions (theoretical):

Mg:  0.0000  0.0000  0.0000 
Mg:  0.9913  0.2761  0.2500 
Si:  0.4270  0.0940  0.2500 
O:  0.7685  0.0916  0.2500 
O:  0.2222  0.4456  0.2500 
O:  0.2754  0.1636  0.0314 
Mg:  0.5000  0.5000  0.0000 
Mg:  0.4913  0.2239  0.7500 
Si:  0.9270  0.4060  0.7500 
O:  0.2685  0.4084  0.7500 
O:  0.7222  0.0544  0.7500 
O:  0.7754  0.3364  0.9686 
Mg:  0.0000  0.0000  0.5000 
Mg:  0.0087  0.7239  0.7500 
Si:  0.5730  0.9060  0.7500 
O:  0.2315  0.9084  0.7500 
O:  0.7778  0.5544  0.7500 
O:  0.7246  0.8364  0.5314 
Mg:  0.5000  0.5000  0.5000 
Mg:  0.5087  0.7761  0.2500 
Si:  0.0730  0.5940  0.2500 
O:  0.7315  0.5916  0.2500 
O:  0.2778  0.9456  0.2500 
O:  0.2246  0.6636  0.4686 
O:  0.7246  0.8364  0.9686 
O:  0.2246  0.6636  0.0314 
O:  0.2754  0.1636  0.4686 
O:  0.7754  0.3364  0.5314 
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
Au
105
105
105
105
5
B2u
147
147
148
147
6
B2g
178
178
178
178
7
Au
186
186
186
186
8
A1g
190
190
190
190
8.142e+37
0.1
5.258e+37
0.1
1.340e+38
0.2
9
B3g
197
197
197
197
4.476e+37
0.1
6.155e+37
0.1
1.063e+38
0.2
10
B1u
200
200
200
200
11
B3u
206
207
206
206
12
B1g
225
225
225
225
13
A1g
227
227
227
227
1.530e+39
2.5
1.835e+37
0.0
1.549e+39
2.6
14
B2g
250
250
250
250
1.334e+38
0.2
1.834e+38
0.3
3.167e+38
0.5
15
Au
251
251
251
251
16
B1g
258
258
258
258
3.018e+37
0.0
4.150e+37
0.1
7.168e+37
0.1
17
B3u
280
280
280
280
18
B1u
283
283
283
284
19
B2u
285
285
285
285
20
B3g
288
288
288
288
8.558e+36
0.0
1.177e+37
0.0
2.033e+37
0.0
21
B2u
297
297
299
297
22
B1u
299
299
301
301
23
B1u
301
301
301
301
24
B1u
301
303
314
311
25
B1u
316
316
316
318
26
A1g
318
318
318
321
1.680e+39
2.8
8.990e+37
0.1
1.769e+39
2.9
27
B3g
322
322
322
322
8.336e+37
0.1
1.146e+38
0.2
1.980e+38
0.3
28
B3u
323
325
323
323
29
B1g
328
328
328
328
2.076e+37
0.0
2.855e+37
0.0
4.932e+37
0.1
30
B2g
332
332
332
332
1.656e+37
0.0
2.277e+37
0.0
3.933e+37
0.1
31
A1g
336
336
336
336
7.153e+38
1.2
4.671e+38
0.8
1.182e+39
2.0
32
Au
349
349
349
349
33
A1g
357
357
357
357
7.555e+38
1.2
5.415e+38
0.9
1.297e+39
2.1
34
B2u
364
364
364
364
2.894e+37
0.0
3.979e+37
0.1
6.873e+37
0.1
35
B1g
364
364
374
364
1.151e+38
0.2
1.583e+38
0.3
2.734e+38
0.5
36
B2g
374
374
381
374
5.480e+37
0.1
7.536e+37
0.1
1.302e+38
0.2
37
B3g
387
387
387
387
8.131e+38
1.3
1.118e+39
1.8
1.931e+39
3.2
38
B1g
387
387
387
387
9.433e+36
0.0
1.297e+37
0.0
2.240e+37
0.0
39
Au
392
392
392
392
40
B3u
398
401
398
398
41
B2u
402
402
412
402
42
B3u
412
420
420
412
43
B3g
420
425
423
420
1.208e+36
0.0
1.661e+36
0.0
2.869e+36
0.0
44
B1u
425
429
425
428
45
B1u
429
430
429
430
46
B2u
430
436
436
436
47
A1g
436
438
438
438
9.905e+38
1.6
5.433e+38
0.9
1.534e+39
2.5
48
Au
438
446
446
446
49
B1g
446
451
447
451
3.519e+38
0.6
4.838e+38
0.8
8.357e+38
1.4
50
B2g
451
464
451
456
1.518e+38
0.3
2.087e+38
0.3
3.605e+38
0.6
51
B2u
464
473
480
464
52
B1u
480
480
483
483
53
B3u
483
484
484
484
54
Au
484
484
492
494
55
B1u
508
508
508
508
56
B2u
508
508
509
509
57
B3u
509
514
514
514
58
Au
514
532
522
532
59
B2u
532
533
534
534
60
B3u
534
540
540
540
61
A1g
540
552
573
578
7.493e+38
1.2
1.927e+38
0.3
9.419e+38
1.6
62
B1g
578
578
578
579
3.358e+38
0.6
4.618e+38
0.8
7.976e+38
1.3
63
B2g
579
579
579
581
6.414e+38
1.1
8.819e+38
1.5
1.523e+39
2.5
64
B3g
587
587
587
587
5.897e+38
1.0
8.109e+38
1.3
1.401e+39
2.3
65
B3u
603
606
603
603
66
A1g
606
628
606
606
6.589e+39
10.9
2.865e+38
0.5
6.876e+39
11.4
67
B2u
628
628
628
628
68
B1g
628
649
628
628
8.623e+37
0.1
1.186e+38
0.2
2.048e+38
0.3
69
A1g
819
819
819
819
5.994e+40
99.0
6.216e+38
1.0
6.056e+40
100.0
70
B2u
828
828
828
828
71
B3u
828
829
832
828
72
B1g
832
832
832
832
5.409e+38
0.9
7.437e+38
1.2
1.285e+39
2.1
73
A1g
849
849
849
849
3.454e+40
57.0
8.031e+38
1.3
3.534e+40
58.4
74
B1g
858
858
858
858
2.256e+39
3.7
3.102e+39
5.1
5.358e+39
8.8
75
B1u
867
867
867
867
76
B2u
867
867
875
875
77
B2g
875
875
904
904
3.287e+39
5.4
4.519e+39
7.5
7.806e+39
12.9
78
Au
904
904
914
914
79
B3g
914
914
956
956
2.269e+39
3.7
3.120e+39
5.2
5.389e+39
8.9
80
B3u
956
961
961
961
81
A1g
961
961
961
972
6.165e+39
10.2
3.373e+39
5.6
9.538e+39
15.7
82
B1g
972
972
972
973
1.617e+38
0.3
2.224e+38
0.4
3.841e+38
0.6
83
B3u
973
982
973
982
84
B2u
982
1072
989
988
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.