- DOLOMITE - CaMg(CO₃)₂

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:	148		R-3
Lattice parameters (Å):	4.8064	4.8064		16.0060
Angles (°):	90	90		120

Symmetry (theoretical):

Space group:	148		R-3
Lattice parameters (Å):	5.8755	5.8755		5.8755
Angles (°):	48.00	48.00		48.00

Cell contents:

Number of atoms:	10
Number of atom types:	4
Chemical composition:	0

Atomic positions (theoretical):

Ca:	0.0000	0.0000	0.0000
Mg:	0.5000	0.5000	0.5000
C:	0.2423	0.2423	0.2423
O:	0.4884	0.9590	0.2827
O:	0.9590	0.2827	0.4884
O:	0.2827	0.4884	0.9590
C:	0.7577	0.7577	0.7577
O:	0.5116	0.0410	0.7173
O:	0.0410	0.7173	0.5116
O:	0.7173	0.5116	0.0410

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	142	142	142	151
5	Eu	151	151	151	151
6	Eu	151	173	173	184
7	Eg	184	184	184	184	6.184e+39 7.3	6.726e+39 8.0	1.291e+40 15.3
8	Eg	184	184	184	192	6.184e+39 7.3	7.757e+39 9.2	1.394e+40 16.5
9	Ag	221	221	221	221	2.411e+38 0.3	1.657e+38 0.2	4.068e+38 0.5
10	Eu	287	287	287	287
11	Eu	287	298	298	287
12	Eg	322	322	322	322	8.691e+39 10.3	1.464e+40 17.3	2.333e+40 27.6
13	Eg	322	322	322	322	8.691e+39 10.3	8.923e+39 10.6	1.761e+40 20.9
14	Au	344	344	344	347
15	Ag	362	362	362	362	2.909e+37 0.0	2.070e+37 0.0	4.979e+37 0.1
16	Eu	386	386	386	386
17	Eu	386	394	394	386
18	Au	394	470	470	468
19	Eg	721	721	721	721	2.599e+39 3.1	3.226e+39 3.8	5.825e+39 6.9
20	Eg	721	721	721	721	2.599e+39 3.1	2.063e+39 2.4	4.662e+39 5.5
21	Eu	727	727	727	727
22	Eu	727	730	730	727
23	Au	849	849	849	857
24	Ag	857	857	857	873	5.570e+38 0.7	4.065e+36 0.0	5.610e+38 0.7
25	Ag	1109	1109	1109	1109	8.186e+40 97.0	2.536e+39 3.0	8.440e+40 100.0
26	Au	1109	1109	1109	1110
27	Eu	1442	1442	1442	1442
28	Eu	1442	1461	1461	1442
29	Eg	1461	1461	1461	1461	2.280e+39 2.7	2.276e+39 2.7	4.556e+39 5.4
30	Eg	1461	1592	1592	1461	2.280e+39 2.7	3.036e+39 3.6	5.316e+39 6.3

No.

Char.

ω TO

ω LOx

ω LOy

ω LOz

I ∥

I ⊥