- COESITE - SiO₂

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:	15	C2/c
Lattice parameters (Å):
Angles (°):

Symmetry (theoretical):

Space group:	15		C2/c
Lattice parameters (Å):	7.0695	7.0695		7.1148
Angles (°):	75.36	104.63		59.81

Cell contents:

Number of atoms:	24
Number of atom types:	2
Chemical composition:	0

Atomic positions (theoretical):

Si:	0.2481	0.9699	0.0717
Si:	0.6650	0.6503	0.5421
O:	0.0000	0.0000	0.0000
O:	0.6141	0.6141	0.7500
O:	0.3876	0.8634	0.9364
O:	0.4166	0.7889	0.3272
O:	0.2324	0.1914	0.4753
Si:	0.9699	0.2481	0.4283
Si:	0.6503	0.6650	0.9579
O:	0.0000	0.0000	0.5000
O:	0.8634	0.3876	0.5636
O:	0.7889	0.4166	0.1728
O:	0.1914	0.2324	0.0247
Si:	0.7519	0.0301	0.9283
Si:	0.3350	0.3497	0.4579
O:	0.3859	0.3859	0.2500
O:	0.6124	0.1366	0.0636
O:	0.5834	0.2111	0.6728
O:	0.7676	0.8086	0.5247
Si:	0.0301	0.7519	0.5717
Si:	0.3497	0.3350	0.0421
O:	0.1366	0.6124	0.4364
O:	0.2111	0.5834	0.8272
O:	0.8086	0.7676	0.9753

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	u	0	0	0	0
2	u	0	0	0	0
3	u	0	0	0	0
4	Bg	77	77	77	77	9.307e+38 1.4	9.977e+38 1.5	1.928e+39 2.9
5	Au	111	111	111	111
6	Ag	125	125	125	125	6.890e+39 10.5	1.034e+39 1.6	7.924e+39 12.1
7	Bu	137	137	137	137
8	Bg	144	144	144	144	1.218e+39 1.9	2.055e+39 3.1	3.273e+39 5.0
9	Au	145	145	145	145
10	Ag	177	177	177	177	7.138e+39 10.9	1.624e+39 2.5	8.762e+39 13.4
11	Au	179	179	179	179
12	Bg	192	192	192	192	1.279e+38 0.2	1.865e+38 0.3	3.144e+38 0.5
13	Ag	198	198	198	198	1.986e+39 3.0	1.575e+39 2.4	3.561e+39 5.4
14	Bg	235	235	235	235	1.242e+38 0.2	1.566e+38 0.2	2.808e+38 0.4
15	Bu	244	244	244	244
16	Au	254	254	255	254
17	Ag	262	262	262	262	1.262e+40 19.3	2.564e+38 0.4	1.288e+40 19.6
18	Bu	264	264	264	264
19	Bg	280	280	280	280	5.673e+36 0.0	6.339e+36 0.0	1.201e+37 0.0
20	Au	283	283	286	283
21	Bu	286	286	287	286
22	Bu	292	292	292	292
23	Bg	305	305	305	305	1.894e+38 0.3	3.137e+38 0.5	5.031e+38 0.8
24	Ag	318	318	318	318	1.978e+39 3.0	5.625e+38 0.9	2.541e+39 3.9
25	Au	318	318	319	318
26	Bu	330	332	330	337
27	Ag	344	344	344	344	8.639e+38 1.3	7.161e+38 1.1	1.580e+39 2.4
28	Bu	361	365	361	361
29	Au	365	369	369	365
30	Bg	369	371	377	369	2.040e+38 0.3	2.219e+38 0.3	4.259e+38 0.6
31	Bu	381	390	381	381
32	Au	407	407	407	407
33	Bu	407	411	414	414
34	Ag	414	414	414	425	4.039e+39 6.2	5.316e+38 0.8	4.570e+39 7.0
35	Bu	428	430	428	430
36	Bg	430	441	430	441	1.870e+38 0.3	3.120e+38 0.5	4.989e+38 0.8
37	Au	441	448	448	448
38	Bg	448	455	455	455	1.634e+37 0.0	2.010e+37 0.0	3.643e+37 0.1
39	Ag	455	459	460	475	1.737e+39 2.6	3.071e+38 0.5	2.044e+39 3.1
40	Au	477	477	482	477
41	Ag	509	509	509	509	6.543e+40 99.8	1.180e+38 0.2	6.555e+40 100.0
42	Bg	529	529	529	529	5.711e+37 0.1	8.686e+37 0.1	1.440e+38 0.2
43	Au	538	538	577	538
44	Bu	584	616	584	584
45	Bg	647	647	647	647	2.961e+37 0.0	3.832e+37 0.1	6.793e+37 0.1
46	Ag	658	658	658	658	7.160e+38 1.1	3.997e+37 0.1	7.560e+38 1.2
47	Au	661	661	663	661
48	Bu	669	674	669	693
49	Bg	777	777	777	777	1.001e+38 0.2	1.099e+38 0.2	2.100e+38 0.3
50	Ag	780	780	780	780	8.590e+38 1.3	7.174e+38 1.1	1.576e+39 2.4
51	Bu	787	790	787	789
52	Au	806	806	809	806
53	Ag	809	809	809	809	1.272e+39 1.9	6.369e+38 1.0	1.909e+39 2.9
54	Bg	814	814	814	814	1.407e+37 0.0	2.342e+37 0.0	3.749e+37 0.1
55	Au	831	831	831	831
56	Ag	831	831	832	831	5.071e+38 0.8	4.387e+38 0.7	9.458e+38 1.4
57	Bu	1033	1034	1033	1033
58	Ag	1034	1037	1034	1034	6.202e+38 0.9	5.311e+38 0.8	1.151e+39 1.8
59	Bg	1037	1038	1037	1037	1.180e+38 0.2	1.426e+38 0.2	2.606e+38 0.4
60	Bu	1063	1064	1063	1064
61	Au	1064	1065	1065	1065
62	Bg	1065	1069	1069	1069	2.580e+38 0.4	4.333e+38 0.7	6.913e+38 1.1
63	Au	1069	1070	1070	1070
64	Ag	1070	1078	1089	1075	1.393e+38 0.2	1.529e+38 0.2	2.922e+38 0.4
65	Bu	1089	1138	1138	1138
66	Bg	1138	1140	1138	1140	8.829e+38 1.3	9.410e+38 1.4	1.824e+39 2.8
67	Au	1140	1148	1148	1144
68	Bu	1148	1155	1155	1155
69	Ag	1155	1171	1171	1171	6.238e+38 1.0	6.676e+38 1.0	1.291e+39 2.0
70	Bg	1171	1212	1191	1214	1.180e+38 0.2	1.401e+38 0.2	2.582e+38 0.4
71	Bu	1214	1225	1214	1225
72	Au	1225	1239	1266	1250

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.

Normalized

Raw

Options for intensity.

Nx:
Ny:
Nz:

- COESITE - SiO2