- SMITHSONITE - ZnCO₃

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:	167		R-3c
Lattice parameters (Å):	4.6528	4.6528		15.0250
Angles (°):	90.0	90.0		120.0

Symmetry (theoretical):

Space group:	167		R-3c
Lattice parameters (Å):	5.5675	5.5675		5.5675
Angles (°):	49.1	49.1		49.1

Cell contents:

Number of atoms:	10
Number of atom types:	3
Chemical composition:	0

Atomic positions (theoretical):

Zn:	0.0000	0.0000	0.0000
C:	0.2500	0.2500	0.2500
O:	0.5259	0.9741	0.2500
O:	0.9741	0.2500	0.5259
Zn:	0.5000	0.5000	0.5000
C:	0.7500	0.7500	0.7500
O:	0.7500	0.4741	0.0259
O:	0.2500	0.5259	0.9741
O:	0.4741	0.0259	0.7500
O:	0.0259	0.7500	0.4741

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	A2u	148	148	148	168
5	Eu	168	168	168	168
6	Eu	168	169	169	198
7	Eu	198	198	198	198
8	Eu	198	207	207	207
9	Eg	207	207	207	207	6.084e+39 3.6	7.882e+39 4.7	1.397e+40 8.3
10	Eg	207	221	221	221	6.084e+39 3.6	5.243e+39 3.1	1.133e+40 6.8
11	A1u	221	233	233	231
12	A2g	296	296	296	296
13	Eu	300	300	300	300
14	Eu	300	307	307	300
15	Eg	307	307	307	307	2.070e+40 12.4	2.904e+40 17.3	4.974e+40 29.7
16	Eg	307	352	352	307	2.070e+40 12.4	2.532e+40 15.1	4.602e+40 27.5
17	A2u	352	367	367	395
18	A2g	418	418	418	418
19	Eg	720	720	720	720	3.820e+39 2.3	4.084e+39 2.4	7.904e+39 4.7
20	Eg	720	720	720	720	3.820e+39 2.3	3.618e+39 2.2	7.438e+39 4.4
21	Eu	734	734	734	734
22	Eu	734	737	737	734
23	A2u	830	830	830	840
24	A2g	840	840	840	851
25	A1u	1098	1098	1098	1098
26	A1g	1099	1099	1099	1099	1.642e+41 98.0	3.343e+39 2.0	1.675e+41 100.0
27	Eu	1412	1412	1412	1412
28	Eu	1412	1418	1418	1412
29	Eg	1418	1418	1418	1418	1.226e+40 7.3	2.065e+40 12.3	3.290e+40 19.6
30	Eg	1418	1574	1574	1418	1.226e+40 7.3	1.307e+40 7.8	2.533e+40 15.1

No.

Char.

ω TO

ω LOx

ω LOy

ω LOz

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