- ANHYDRITE - CaSO₄

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:	2		P-1
Lattice parameters (Å):	6.9930	6.9950		6.2450
Angles (°):	90	90		90

Symmetry (theoretical):

Space group:	2		P-1
Lattice parameters (Å):	5.3755	5.3755		5.5136
Angles (°):

Cell contents:

Number of atoms:	12
Number of atom types:	3
Chemical composition:	0

Atomic positions (theoretical):

Ca:	0.7500	0.2500	0.3944
S:	0.2500	0.7500	0.0916
O:	0.3849	0.8849	0.9421
O:	0.0727	0.9273	0.2624
Ca:	0.2500	0.7500	0.6056
S:	0.7500	0.2500	0.9084
O:	0.6151	0.1151	0.0579
O:	0.5727	0.4273	0.7376
O:	0.1151	0.6151	0.9421
O:	0.4273	0.5727	0.2624
O:	0.8849	0.3849	0.0579
O:	0.9273	0.0727	0.7376

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	Au	-176	-176	-176	-176
2	Ag	-169	-169	-169	-169
3	Au	-106	-106	-61	-106
4	Ag	-61	-61	-50	-61
5	Ag	-50	-50	-8	-50
6	ac	0	0	0	0
7	ac	0	0	0	0
8	ac	0	0	0	0
9	Ag	148	148	148	148	2.779e+40 21.9	1.919e+39 1.5	2.970e+40 23.4
10	Ag	154	154	154	154	6.937e+38 0.5	9.539e+38 0.8	1.648e+39 1.3
11	Au	273	304	273	273
12	Ag	307	307	307	307	5.173e+39 4.1	7.113e+39 5.6	1.229e+40 9.7
13	Ag	347	347	347	347	5.060e+38 0.4	6.957e+38 0.5	1.202e+39 0.9
14	Au	384	384	384	384
15	Au	412	412	412	412
16	Ag	439	439	439	439	4.178e+38 0.3	5.744e+38 0.5	9.922e+38 0.8
17	Ag	522	522	522	522	3.861e+39 3.0	2.598e+39 2.0	6.459e+39 5.1
18	Au	525	526	525	525
19	Ag	526	526	526	526	1.104e+39 0.9	1.518e+39 1.2	2.622e+39 2.1
20	Au	557	557	557	574
21	Au	574	601	574	600
22	Au	608	608	626	608
23	Ag	646	646	646	646	1.879e+37 0.0	2.584e+37 0.0	4.462e+37 0.0
24	Au	648	648	648	648
25	Ag	660	660	660	660	2.790e+40 22.0	6.768e+39 5.3	3.467e+40 27.3
26	Ag	662	662	662	662	2.188e+39 1.7	3.008e+39 2.4	5.196e+39 4.1
27	Au	704	704	704	755
28	Ag	784	784	784	784	3.408e+40 26.9	1.760e+40 13.9	5.169e+40 40.8
29	Au	1061	1067	1061	1061
30	Au	1067	1089	1067	1073
31	Ag	1089	1126	1089	1089	1.232e+41 97.2	3.595e+39 2.8	1.268e+41 100.0
32	Ag	1126	1193	1126	1126	5.433e+39 4.3	7.471e+39 5.9	1.290e+40 10.2
33	Au	1274	1274	1274	1277
34	Ag	1277	1277	1277	1283	8.254e+40 65.1	1.763e+40 13.9	1.002e+41 79.0
35	Au	1283	1283	1337	1342
36	Ag	1342	1342	1342	1356	1.512e+39 1.2	2.079e+39 1.6	3.591e+39 2.8

No.

Char.

ω TO

ω LOx

ω LOy

ω LOz

I ∥

I ⊥