Atoms: Nb₂O₂Br₄

Structure info
Layer group	pm2m
Layer group number	27
Structure origin	exfoliated02-21
ICSD id of parent bulk structure	ICSD 416669

Stability
Energy above convex hull [eV/atom]	0.000
Heat of formation [eV/atom]	-1.660
Dynamically stable	Yes

Basic properties
Magnetic state	NM
Band gap [eV]	1.038
Band gap (HSE06) [eV]	1.923

Repeat: 1234   Download: XYZ CIF JSON

Axis	x [Å]	y [Å]	z [Å]	Periodic
1	3.944	0.000	0.000	Yes
2	0.000	7.070	0.000	Yes
3	0.000	0.000	34.045	No

Lengths [Å]	3.944	7.070	34.045
Angles [°]	90.000	90.000	90.000

Convex hull

Nb2O2Br4 (2NbOBr2-1)
Heat of formation [eV/atom]	-1.66
Energy above convex hull [eV/atom]	0.00

Monolayers from C2DB
Nb4O8, (4NbO2-1)	-2.42 eV/atom
Nb2O4, (2NbO2-1)	-2.38 eV/atom
NbO2, (1NbO2-1)	-2.37 eV/atom
NbO2, (1NbO2-2)	-2.35 eV/atom
Br2Nb2O4, (2BrNbO2-1)	-2.23 eV/atom
NbO2, (1NbO2-3)	-2.20 eV/atom
Nb2O6, (2NbO3-1)	-2.07 eV/atom
Nb4O12, (4NbO3-1)	-1.83 eV/atom
Br2Nb2O2, (2BrNbO-1)	-1.67 eV/atom
Nb2O2Br4, (2NbOBr2-1)	-1.66 eV/atom
Nb2O2, (2NbO-1)	-1.53 eV/atom
Nb2O2, (2NbO-2)	-1.30 eV/atom
ONb3Br7, (1ONb3Br7-1)	-1.15 eV/atom
Nb2O2, (2NbO-3)	-1.02 eV/atom
Nb3Br8, (1Nb3Br8-1)	-0.98 eV/atom
Nb2Br6, (2NbBr3-1)	-0.92 eV/atom
Nb2Br6, (2NbBr3-2)	-0.84 eV/atom
Nb2Br6, (2NbBr3-3)	-0.80 eV/atom
Nb2Br4, (2NbBr2-1)	-0.78 eV/atom
NbBr2, (1NbBr2-1)	-0.65 eV/atom
NbBr2, (1NbBr2-2)	-0.58 eV/atom
NbBr2, (1NbBr2-3)	-0.35 eV/atom
Br2Nb2, (2BrNb-1)	-0.02 eV/atom
Br2Nb2, (2BrNb-2)	0.07 eV/atom

Bulk crystals from OQMD123
Nb2O5	-2.77 eV/atom
Nb8O16	-2.64 eV/atom
Nb3O3	-2.08 eV/atom
Br4Nb2O2	-1.65 eV/atom
Br12Nb4O4	-1.46 eV/atom
Br16Nb6	-0.97 eV/atom
Br10Nb2	-0.90 eV/atom
Br4	0.00 eV/atom
Nb	0.00 eV/atom
O8	0.00 eV/atom
Br8O4	0.17 eV/atom
Br16O24	0.27 eV/atom

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	81.40	5.17	-0.00
yy	3.85	64.67	-0.00
xy	0.00	0.00	28.91

Stiffness tensor eigenvalues
Eigenvalue 0	28.91 N/m
Eigenvalue 1	63.55 N/m
Eigenvalue 2	82.52 N/m

Phonons

Property	Value
Minimum eigenvalue of Hessian [eV/Ų]	-0.00

Deformation potentials

DVB (eV)	xx	yy	xy
Γ	1.22	2.66	0.00
X	0.97	2.67	0.00
S	1.41	-1.58	-0.00
Y	2.30	-1.75	-0.00
kVBM	0.97	2.67	0.00

	xx	yy	xy
Band Gap	7.97	-3.20	0.00

DCB (eV)	xx	yy	xy
Γ	10.88	-2.05	0.00
X	0.30	-7.11	0.00
S	0.28	0.22	0.00
Y	8.94	-0.53	0.00
kCBM	8.94	-0.53	0.00

Band structure and DOS

Effective masses

Property (VBM)	Value
Min eff. mass	4.68 m0
Max eff. mass	53.30 m0
DOS eff. mass	12.98 m0
Crystal coordinates	[0.500, 0.007]
Warping parameter	-0.015
Barrier height	> 3.4 meV
Distance to barrier	> 0.0162 Å-1

Property (CBM)	Value
Min eff. mass	0.09 m0
Max eff. mass	∞
DOS eff. mass	∞
Crystal coordinates	[-0.000, 0.499]
Warping parameter	0.166
Barrier height	> 29.1 meV
Distance to barrier	> 0.0159 Å-1

Electronic band structure (HSE06@PBE)

Property	Value
KVP: Band gap (HSE06) [eV]	1.92
KVP: Direct band gap (HSE06) [eV]	2.07
Valence band maximum wrt. vacuum level (HSE06)	-5.95 eV
Conduction band minimum wrt. vacuum level (HSE06)	-4.03 eV

Born charges

ZNbij	ux	uy	uz
Px	6.53	-0.02	-0.00
Py	-0.38	3.65	0.00
Pz	0.00	0.00	0.61

ZBrij	ux	uy	uz
Px	-0.23	-0.00	-0.11
Py	-0.00	-0.50	-0.00
Pz	-0.02	-0.00	-0.24

ZBrij	ux	uy	uz
Px	-0.34	-0.00	0.03
Py	-0.00	-1.95	0.00
Pz	0.01	-0.00	-0.18

ZOij	ux	uy	uz
Px	-5.96	0.10	0.00
Py	0.41	-1.20	-0.00
Pz	-0.00	-0.00	-0.19

ZBrij	ux	uy	uz
Px	-0.34	0.00	-0.03
Py	0.00	-1.95	0.00
Pz	-0.01	-0.00	-0.18

ZNbij	ux	uy	uz
Px	6.53	0.02	0.00
Py	0.38	3.65	0.00
Pz	-0.00	0.00	0.61

ZBrij	ux	uy	uz
Px	-0.23	0.00	0.11
Py	0.00	-0.50	-0.00
Pz	0.02	-0.00	-0.24

ZOij	ux	uy	uz
Px	-5.96	-0.10	-0.00
Py	-0.41	-1.20	-0.00
Pz	0.00	-0.00	-0.19

Optical polarizability

Properties
Static interband polarizability at (x) [Å]	1.844
Static interband polarizability at (y) [Å]	2.884
Static interband polarizability at (z) [Å]	0.390

Infrared polarizability

Static polarizability	[Å]
Phonons only (x)	2.73
Phonons only (y)	2.38
Phonons only (z)	0.02
Total (phonons + electrons) (x)	4.57
Total (phonons + electrons) (y)	5.26
Total (phonons + electrons) (z)	0.41

Bader charges

#	Chemical symbol	Charges [|e|]
0	Nb	1.99
1	Br	-0.50
2	Br	-0.45
3	Nb	1.98
4	Br	-0.50
5	Br	-0.45
6	O	-1.03
7	O	-1.03

Piezoelectric tensor

cij (e/Ådim-1)	xx	yy	xy
x	1.27	-0.02	0.00
y	-0.00	-0.00	0.04
z	-0.00	-0.00	0.00

cclampedij (e/Ådim-1)	xx	yy	xy
x	-0.00	0.01	0.00
y	-0.00	0.00	0.03
z	-0.00	0.00	0.00

Miscellaneous

Miscellaneous details
Unique ID	2NbOBr2-1
Number of atoms	8
Number of species	3
Formula	Nb2O2Br4
Reduced formula	NbOBr2
Stoichiometry	ABC2
Unit cell area [Å2]	27.885
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/ICSD-COD/3el/Nb4Br8O4
Old uid	Nb2O2Br4-7d127da2c220
Inversion symmetry	No
Layer group	pm2m
Layer group number	27
Structure origin	exfoliated02-21
Band gap [eV]	1.038
gap_dir	1.187
gap_dir_nosoc	1.192
Vacuum level [eV]	1.814
Fermi level [eV]	-3.317
minhessianeig	-0.000
Dynamically stable	Yes
Band gap (HSE06) [eV]	1.923

Miscellaneous details
gap_dir_hse	2.073
vbm_hse	-4.137
cbm_hse	-2.214
Static interband polarizability at (x) [Å]	1.844
Static interband polarizability at (y) [Å]	2.884
Static interband polarizability at (z) [Å]	0.390
Static polarizability (phonons) (x) [Å]	2.725
Static polarizability (phonons + electrons) (x) [Å]	4.569
Static polarizability (phonons) (y) [Å]	2.376
Static polarizability (phonons + electrons) (y) [Å]	5.260
Static polarizability (phonons) (z) [Å]	0.023
Static polarizability (phonons + electrons) (z) [Å]	0.413
Energy [eV]	-50.516
ICSD id of parent bulk structure	ICSD 416669
Magnetic state	NM
Spin axis	z
Magnetic anisotropy energy, xz [meV/unit cell]	0.000
Magnetic anisotropy energy, yz [meV/unit cell]	0.000
Energy above convex hull [eV/atom]	0.000
Heat of formation [eV/atom]	-1.660