- MONTICELLITE - MgCaSiO₄

Theoretical atomic positions and lattice parameters at experimental volum from 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):	2.5512	5.8765		3.3767
Angles (°):	90.0	90.0		90.0

Symmetry (theoretical):

Space group:	62		Pbnm
Lattice parameters (Å):	4.7976	11.1791		6.3696
Angles (°):	90.0	90.0		90.0

Cell contents:

Number of atoms:	28
Number of atom types:	4
Chemical composition:	0

Atomic positions (theoretical):

Mg:	0.0000	0.0000	0.0000
Ca:	0.9786	0.2750	0.2500
Si:	0.4097	0.0790	0.2500
O:	0.7453	0.0763	0.2500
O:	0.2506	0.4490	0.2500
O:	0.2710	0.1442	0.0460
Mg:	0.5000	0.5000	0.0000
Ca:	0.4786	0.2250	0.7500
Si:	0.9097	0.4210	0.7500
O:	0.2453	0.4237	0.7500
O:	0.7506	0.0510	0.7500
O:	0.7710	0.3558	0.9540
Mg:	0.0000	0.0000	0.5000
Ca:	0.0214	0.7250	0.7500
Si:	0.5903	0.9210	0.7500
O:	0.2547	0.9237	0.7500
O:	0.7494	0.5510	0.7500
O:	0.7290	0.8558	0.5460
Mg:	0.5000	0.5000	0.5000
Ca:	0.5214	0.7750	0.2500
Si:	0.0903	0.5790	0.2500
O:	0.7547	0.5763	0.2500
O:	0.2494	0.9490	0.2500
O:	0.2290	0.6442	0.4540
O:	0.7290	0.8558	0.9540
O:	0.2290	0.6442	0.0460
O:	0.2710	0.1442	0.4540
O:	0.7710	0.3558	0.5460

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	ac	0	0	0	0
2	ac	0	0	0	0
3	ac	0	0	0	0
4	Au	97	97	97	97
5	B2u	119	119	122	119
6	B2g	140	140	140	140	1.943e+37 0.0	2.671e+37 0.0	4.614e+37 0.1
7	A1g	145	145	145	145	5.303e+38 1.0	1.122e+38 0.2	6.424e+38 1.2
8	B1g	163	163	163	163	2.968e+38 0.5	4.081e+38 0.7	7.050e+38 1.3
9	B3u	169	170	169	169
10	A1g	170	171	170	170	5.793e+38 1.0	9.175e+37 0.2	6.711e+38 1.2
11	Au	173	173	173	173
12	B1u	174	174	174	190
13	Au	199	199	199	199
14	B3u	200	200	200	200
15	B1u	201	201	201	203
16	B2u	203	203	208	213
17	B1g	213	213	213	213
18	B3g	222	222	222	222	3.610e+37 0.1	4.964e+37 0.1	8.574e+37 0.2
19	B1u	238	238	238	244
20	B2g	244	244	244	244	2.495e+38 0.4	3.430e+38 0.6	5.925e+38 1.1
21	B3g	246	246	246	246	2.757e+38 0.5	3.792e+38 0.7	6.549e+38 1.2
22	B3u	247	249	247	247
23	A1g	257	257	257	257	3.327e+39 6.0	1.417e+38 0.3	3.469e+39 6.2
24	B2g	258	258	258	258	1.308e+36 0.0	1.799e+36 0.0	3.107e+36 0.0
25	B1g	264	264	264	264	5.860e+37 0.1	8.057e+37 0.1	1.392e+38 0.3
26	Au	264	264	264	264
27	B3g	270	270	270	270	1.846e+37 0.0	2.539e+37 0.0	4.385e+37 0.1
28	A1g	282	282	282	282	9.821e+38 1.8	2.842e+37 0.1	1.010e+39 1.8
29	B2u	287	287	293	287
30	B3u	293	297	297	293
31	B2u	297	306	303	297
32	B1u	306	307	306	306
33	B2u	307	308	308	307
34	B1g	308	308	308	308	1.744e+37 0.0	2.398e+37 0.0	4.143e+37 0.1
35	B3u	308	313	313	308
36	Ag	313	313	313	313	5.259e+37 0.1	1.172e+37 0.0	6.432e+37 0.1
37	Ag	313	325	330	313	1.775e+39 3.2	3.956e+38 0.7	2.170e+39 3.9
38	B2g	330	330	330	330	3.008e+37 0.1	4.136e+37 0.1	7.144e+37 0.1
39	B3g	333	333	333	333	5.968e+37 0.1	8.206e+37 0.1	1.417e+38 0.3
40	B1g	343	343	343	343
41	B1u	360	360	360	361
42	Au	362	362	362	362
43	B3u	369	375	369	369
44	B2u	375	389	390	375
45	Au	390	390	399	390
46	B1u	399	399	404	404
47	A1g	404	404	406	406	3.141e+38 0.6	2.343e+38 0.4	5.484e+38 1.0
48	B1g	406	406	406	406	2.035e+39 3.7	2.966e+39 5.3	5.001e+39 9.0
49	B3g	406	406	406	422	5.778e+38 1.0	6.271e+38 1.1	1.205e+39 2.2
50	B2g	422	422	422	431	1.136e+39 2.0	1.562e+39 2.8	2.699e+39 4.9
51	B2u	431	431	439	438
52	B1u	439	439	440	440
53	Au	440	440	445	445
54	B3u	445	451	450	456
55	B3u	463	468	463	463
56	B2u	468	499	469	468
57	B1u	499	505	499	505
58	Au	505	511	505	511
59	B2u	511	514	521	521
60	B3u	521	522	527	527
61	A1g	527	527	545	543	1.012e+39 1.8	7.520e+38 1.4	1.764e+39 3.2
62	B1g	550	550	550	550	3.309e+38 0.6	4.549e+38 0.8	7.858e+38 1.4
63	B2g	557	557	557	557	4.329e+38 0.8	5.953e+38 1.1	1.028e+39 1.8
64	B3g	564	564	564	564	7.898e+37 0.1	1.086e+38 0.2	1.876e+38 0.3
65	B3u	575	577	575	575
66	A1g	577	582	577	577	4.929e+39 8.9	7.449e+38 1.3	5.674e+39 10.2
67	B2u	582	586	583	582
68	B1g	586	610	586	586	1.523e+38 0.3	2.095e+38 0.4	3.618e+38 0.7
69	A1g	801	801	801	801	5.463e+40 98.2	9.740e+38 1.8	5.561e+40 100.0
70	B3u	806	806	806	806
71	B2u	806	807	808	806
72	B1g	810	810	810	810	3.257e+38 0.6	4.479e+38 0.8	7.736e+38 1.4
73	A1g	829	829	829	829	2.658e+40 47.8	2.927e+39 5.3	2.950e+40 53.1
74	B1g	834	834	834	834	5.988e+38 1.1	8.233e+38 1.5	1.422e+39 2.6
75	B1u	853	853	853	859
76	B2u	859	859	860	860
77	B2g	860	860	873	873	2.324e+38 0.4	3.195e+38 0.6	5.519e+38 1.0
78	Au	873	873	882	882
79	B3g	882	882	924	924	3.877e+39 7.0	5.331e+39 9.6	9.209e+39 16.6
80	A1g	924	924	931	931	5.453e+39 9.8	3.212e+39 5.8	8.665e+39 15.6
81	B1g	931	931	931	931	1.256e+38 0.2	1.727e+38 0.3	2.983e+38 0.5
82	B3u	931	936	933	939
83	B3u	939	939	939	939
84	B2u	939	1021	947	953

No.

Char.

ω TO

ω LOx

ω LOy

ω LOz

I ∥

I ⊥