- BORON NITRIDE - BN

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:	194		P6_3/mmc
Lattice parameters (Å):	2.5100	2.5100		6.6900
Angles (°):	90	90		120

Symmetry (theoretical):

Space group:	194		P6_3/mmc
Lattice parameters (Å):	2.4807	2.4807		6.4619
Angles (°):	90	90		120

Cell contents:

Number of atoms:	4
Number of atom types:	2
Chemical composition:	0

Atomic positions (theoretical):

B:	0.3333	0.6667	0.2500
B:	0.6667	0.3333	0.7500
N:	0.3333	0.6667	0.7500
N:	0.6667	0.3333	0.2500

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	E2g	50	50	50	50	4.854e+38 0.1	4.327e+38 0.0	9.181e+38 0.1
5	E2g	50	50	50	50	4.854e+38 0.1	5.989e+38 0.1	1.084e+39 0.1
6	B1g	116	116	116	116
7	A2u	760	760	760	821
8	B1g	821	821	821	829
9	E1u	1390	1390	1390	1390
10	E1u	1390	1390	1390	1390
11	E2g	1390	1390	1390	1390	4.358e+41 46.3	5.050e+41 53.7	9.409e+41 100.0
12	E2g	1390	1621	1621	1390	4.358e+41 46.3	4.211e+41 44.8	8.569e+41 91.1

No.

Char.

ω TO

ω LOx

ω LOy

ω LOz

I ∥

I ⊥