- CUMMINGTONITE - Mg₇Si₈O₂₂(OH)₂

2GPa under construction

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:	12		C2/m
Lattice parameters (Å):	9.5015	18.1289		5.3089
Angles (°):	90	102.090		90

Symmetry (theoretical):

Space group:	12		C2/m
Lattice parameters (Å):	9.9550	9.9550		5.1782
Angles (°):	83.88	96.11		55.18

Cell contents:

Number of atoms:	41
Number of atom types:	4
Chemical composition:	0

Atomic positions (theoretical):

Mg:	0.0852	0.0852	0.5000
Mg:	0.1748	0.1748	1.0000
Mg:	1.0000	1.0000	1.0000
Mg:	0.2522	0.2522	0.5000
Si:	0.3778	0.7907	0.2858
Si:	0.4716	0.8694	0.7905
O:	0.2015	0.9699	0.2134
O:	0.2937	0.0498	0.7199
O:	0.1169	0.8831	0.7128
O:	0.6273	0.8702	0.7608
O:	0.4977	0.7823	0.0925
O:	0.4687	0.7567	0.5860
O:	0.3534	0.6466	0.2558
H:	0.2247	0.7753	0.7578
Si:	0.7907	0.3778	0.7142
Si:	0.8694	0.4716	0.2095
O:	0.9699	0.2015	0.7866
O:	0.0498	0.2937	0.2801
O:	0.8831	0.1169	0.2872
O:	0.8702	0.6273	0.2392
O:	0.7823	0.4977	0.9075
O:	0.7567	0.4687	0.4140
O:	0.6466	0.3534	0.7442
H:	0.7753	0.2247	0.2422
Mg:	0.9148	0.9148	0.5000
Mg:	0.8252	0.8252	1.0000
Mg:	0.7478	0.7478	0.5000
Si:	0.6222	0.2093	0.7142
Si:	0.5284	0.1306	0.2095
O:	0.7985	0.0301	0.7866
O:	0.7063	0.9502	0.2801
O:	0.3727	0.1298	0.2392
O:	0.5023	0.2177	0.9075
O:	0.5313	0.2433	0.4140
Si:	0.2093	0.6222	0.2858
Si:	0.1306	0.5284	0.7905
O:	0.0301	0.7985	0.2134
O:	0.9502	0.7063	0.7199
O:	0.1298	0.3727	0.7608
O:	0.2177	0.5023	0.0925
O:	0.2433	0.5313	0.5860

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:

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.

Choose the polarization of the lasers.

I ∥

I ⊥

I Total

Horizontal:

Xmin:
Xmax:

Vertical:

Ymin:
Ymax:

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	-39	-39	-39	-39
2	0	0	0	0
3	0	0	0	0
4	0	0	0	0
5	76	80	76	76
6	98	98	98	98
7	103	103	104	103
8	117	117	117	117
9	143	143	143	143
10	156	156	165	156
11	165	165	165	165
12	165	165	169	165
13	173	173	173	173
14	180	180	180	180
15	185	185	185	185
16	197	197	197	197
17	208	209	208	210
18	212	212	212	212
19	230	230	230	230
20	233	233	233	233
21	234	234	234	234
22	235	235	235	235
23	247	247	247	247
24	251	251	251	251
25	255	255	255	255
26	255	255	255	255
27	257	257	257	257
28	261	261	261	261
29	268	273	268	271
30	285	285	285	285
31	291	291	293	291
32	297	297	300	297
33	304	304	304	304
34	304	307	304	304
35	309	309	309	309
36	310	310	310	310
37	310	310	310	310
38	311	315	311	313
39	315	318	318	315
40	332	332	332	332
41	343	351	343	346
42	351	352	351	351
43	352	357	352	352
44	359	359	359	359
45	362	362	362	362
46	369	371	369	370
47	373	373	373	373
48	374	374	374	374
49	377	377	381	377
50	381	381	381	381
51	383	388	383	384
52	389	389	389	389
53	393	393	393	394
54	402	402	402	402
55	409	409	411	409
56	414	414	414	414
57	415	415	415	415
58	418	418	418	420
59	427	429	427	429
60	429	432	430	430
61	434	434	434	434
62	443	443	447	443
63	447	452	450	448
64	452	453	455	452
65	457	457	457	457
66	457	457	457	457
67	459	465	459	465
68	465	470	465	470
69	470	477	478	476
70	478	478	486	478
71	486	489	496	496
72	496	496	498	498
73	498	498	505	498
74	505	505	507	505
75	507	507	516	516
76	516	521	520	522
77	522	522	522	527
78	529	529	541	529
79	541	541	543	541
80	543	543	543	543
81	543	543	545	543
82	545	546	571	561
83	571	576	574	576
84	576	587	576	587
85	587	596	587	612
86	638	639	638	652
87	652	652	652	655
88	655	655	655	657
89	658	662	658	658
90	671	671	671	671
91	674	674	674	674
92	681	681	690	681
93	690	690	701	690
94	753	753	753	754
95	764	764	764	764
96	767	767	770	767
97	782	782	782	782
98	792	792	792	792
99	794	794	794	800
100	897	897	897	897
101	905	905	915	905
102	916	926	916	917
103	931	931	931	931
104	932	932	932	932
105	958	986	958	959
106	986	993	995	986
107	995	995	996	995
108	996	999	997	999
109	999	1003	999	1003
110	1003	1012	1014	1014
111	1014	1014	1016	1024
112	1025	1029	1025	1029
113	1029	1045	1029	1045
114	1045	1050	1045	1050
115	1050	1052	1052	1052
116	1052	1072	1058	1076
117	1077	1082	1077	1082
118	1082	1084	1084	1084
119	1084	1095	1102	1102
120	1102	1102	1123	1123
121	1123	1123	1164	1125
122	3656	3656	3656	3656
123	3656	3657	3656	3656

No.

Char.

ω TO

ω LOx

ω LOy

ω LOz

I ∥

I ⊥