- TALC - Mg₃Si₄O₁₀(OH)₂

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):	5.2900	9.1730		9.4600
Angles (°):	90.46	98.68		90.09

Symmetry (theoretical):

Space group:	2		P-1
Lattice parameters (Å):	5.3307	10.2302		5.3298
Angles (°):	98.26	119.99		85.60

Cell contents:

Number of atoms:	21
Number of atom types:	4
Chemical composition:	0

Atomic positions (theoretical):

Mg:	0.0000	1.0000	0.0000
Mg:	0.6667	1.0000	0.3335
Mg:	0.3333	0.0000	0.6665
Si:	0.0040	0.7294	0.2606
Si:	0.6704	0.7294	0.5934
Si:	0.9960	0.2706	0.7394
Si:	0.3296	0.2706	0.4066
O:	0.6681	0.8907	0.6362
O:	0.3339	0.8976	0.9724
O:	0.0024	0.8907	0.3048
O:	0.8497	0.6748	0.9122
O:	0.8263	0.6743	0.4005
O:	0.3379	0.6743	0.4238
O:	0.3319	0.1093	0.3638
O:	0.6661	0.1024	0.0276
O:	0.9976	0.1093	0.6952
O:	0.1503	0.3252	0.0878
O:	0.1737	0.3257	0.5995
O:	0.6621	0.3257	0.5762
H:	0.3332	0.8028	0.9467
H:	0.6668	0.1972	0.0533

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.

Dielectric Properties

We define:

The Born effective charges, also called dynamical charges, are tensors that correspond to the energy derivative with respect to atomic displacements and electric fields or, equivalently, to the change in atomic force due to an electric field: The sum of the Born effective charges of all nuclei in one cell must vanish, element by element, along each of the three directions of the space.
The dielectric tensors are the energy derivative with respect to two electric fields. They also relate the induced polarization to the external electric field.

Born effective charges (Z):

Mg:	1.9741	0.0670	0.0087
	0.1268	1.6785	-0.0444
	0.0163	-0.0450	2.0117
Eig. Value:	2.0030	1.6437	2.0176
Mg:	2.0092	-0.0346	-0.0043
	-0.0631	1.6781	-0.0402
	-0.0079	-0.0418	1.9828
Eig. Value:	2.0163	1.6656	1.9882
Mg:	2.0092	-0.0346	-0.0043
	-0.0631	1.6781	-0.0402
	-0.0079	-0.0418	1.9828
Eig. Value:	2.0163	1.6656	1.9882
Si:	3.4763	-0.0133	0.0316
	-0.0167	2.4957	-0.1273
	-0.0483	-0.1302	3.4707
Eig. Value:	3.4736	2.4788	3.4904
Si:	3.4838	0.0071	-0.0317
	0.0114	2.5058	-0.1331
	0.0481	-0.1326	3.4542
Eig. Value:	3.4871	2.4875	3.4692
Si:	3.4763	-0.0133	0.0316
	-0.0167	2.4957	-0.1273
	-0.0483	-0.1302	3.4707
Eig. Value:	3.4736	2.4788	3.4904
Si:	3.4838	0.0071	-0.0317
	0.0114	2.5058	-0.1331
	0.0481	-0.1326	3.4542
Eig. Value:	3.4871	2.4875	3.4692
O:	-1.5422	0.0010	0.0076
	-0.0096	-1.7303	-0.0091
	-0.0114	-0.0211	-1.5404
Eig. Value:	-1.5428	-1.7316	-1.5386
O:	-1.4757	0.0024	0.0005
	0.0128	-0.9703	0.0659
	0.0017	0.0665	-1.4679
Eig. Value:	-1.4758	-0.9615	-1.4766
O:	-1.5411	0.0016	-0.0068
	-0.0062	-1.7265	-0.0404
	0.0101	-0.0243	-1.5471
Eig. Value:	-1.5392	-1.7321	-1.5433
O:	-1.0529	0.0141	-0.0029
	0.0081	-1.1119	0.2249
	-0.0024	0.2275	-2.8539
Eig. Value:	-1.0495	-1.0864	-2.8828
O:	-2.4253	-0.1045	0.7850
	-0.1026	-1.0721	0.0633
	0.7863	0.0551	-1.5027
Eig. Value:	-2.8830	-1.0643	-1.0529
O:	-2.4203	0.0955	-0.7830
	0.0972	-1.0996	0.0580
	-0.7850	0.0633	-1.4973
Eig. Value:	-2.8758	-1.0928	-1.0485
O:	-1.5422	0.0010	0.0076
	-0.0096	-1.7303	-0.0091
	-0.0114	-0.0211	-1.5404
Eig. Value:	-1.5428	-1.7316	-1.5386
O:	-1.4757	0.0024	0.0005
	0.0128	-0.9703	0.0659
	0.0017	0.0665	-1.4679
Eig. Value:	-1.4758	-0.9615	-1.4766
O:	-1.5411	0.0016	-0.0068
	-0.0062	-1.7265	-0.0404
	0.0101	-0.0243	-1.5471
Eig. Value:	-1.5392	-1.7321	-1.5433
O:	-1.0529	0.0141	-0.0029
	0.0081	-1.1119	0.2249
	-0.0024	0.2275	-2.8539
Eig. Value:	-1.0495	-1.0864	-2.8828
O:	-2.4253	-0.1045	0.7850
	-0.1026	-1.0721	0.0633
	0.7863	0.0551	-1.5027
Eig. Value:	-2.8830	-1.0643	-1.0529
O:	-2.4203	0.0955	-0.7830
	0.0972	-1.0996	0.0580
	-0.7850	0.0633	-1.4973
Eig. Value:	-2.8758	-1.0928	-1.0485
H:	0.5011	-0.0029	-0.0004
	0.0051	0.1917	-0.0399
	0.0006	-0.0398	0.4958
Eig. Value:	0.5011	0.1866	0.5010
H:	0.5011	-0.0029	-0.0004
	0.0051	0.1917	-0.0399
	0.0006	-0.0398	0.4958
Eig. Value:	0.5011	0.1866	0.5010