Overview: NbI₂

Structure info
Layer group	p-3m1
Layer group number	72
Structure origin	original03-18

Stability
Energy above convex hull [eV/atom]	0.316
Heat of formation [eV/atom]	-0.176
Dynamically stable	No

Basic properties
Magnetic	No
Band gap (PBE) [eV]	0.000

Repeat: 1234   Download: XYZ CIF JSON

Axis	x [Å]	y [Å]	z [Å]	Periodic
1	3.708	-0.000	0.000	Yes
2	-1.854	3.211	0.000	Yes
3	0.000	0.000	18.824	No

Lengths [Å]	3.708	3.708	18.824
Angles [°]	90.000	90.000	120.000

Crystal structure

Symmetries
2D Bravais type	Hexagonal (hp)
Layer group number	72
Layer group	p-3m1
Space group number (bulk in AA-stacking)	164
Space group (bulk in AA-stacking)	P-3m1
Point group	-3m
Inversion symmetry	Yes

Structure data
Formula	NbI2
Stoichiometry	AB2
Number of atoms	3
Unit cell area [Å2]	11.904
Thickness [Å]	3.824

Stability

Convex hull

NbI2 (1NbI2-1)
Heat of formation [eV/atom]	-0.18
Energy above convex hull [eV/atom]	0.32

Monolayers from C2DB
Nb3I8 (1Nb3I8-1)	-0.54 eV/atom
Nb2I6 (2NbI3-1)	-0.42 eV/atom
Nb2I4 (2NbI2-1)	-0.37 eV/atom
Nb2I6 (2NbI3-2)	-0.36 eV/atom
NbI2, (1NbI2-1)	-0.18 eV/atom
NbI2 (1NbI2-2)	-0.12 eV/atom
NbI2 (1NbI2-3)	0.13 eV/atom
Nb2I2 (2INb-1)	0.14 eV/atom
Nb2I2 (2INb-2)	0.15 eV/atom

Bulk crystals from OQMD123
Nb4I16	-0.49 eV/atom
Nb2I6	-0.48 eV/atom
Nb2I10	-0.46 eV/atom
I4	0.00 eV/atom
Nb	0.00 eV/atom

Phonons

Minimum eigenvalue of Hessian [eV/Ų]

-13.60

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	50.97	6.49	0.09
yy	7.47	52.14	0.10
xy	0.00	0.00	43.18

Stiffness tensor eigenvalues
Eigenvalue 0	43.18 N/m
Eigenvalue 1	44.57 N/m
Eigenvalue 2	58.54 N/m

Electronic bands

Band structure and DOS

Key values [eV]
Band gap (PBE)	0.000
Direct band gap (PBE)	0.000
Fermi level wrt. vacuum (PBE)	-3.539

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Nb	1.03
1	I	-0.52
2	I	-0.52

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	51.678
Interband polarizability (y) [Å]	51.678
Interband polarizability (z) [Å]	0.472
Plasma frequency (x) [eV Å0.5]	7.803
Plasma frequency (y) [eV Å0.5]	7.803

Miscellaneous

Miscellaneous details
Unique ID	1NbI2-1
Number of atoms	3
Number of species	2
Formula	NbI2
Reduced formula	NbI2
Stoichiometry	AB2
Unit cell area [Å2]	11.904
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB2/NbI2/NbI2-b7d9cad201ae
Old uid	NbI2-b7d9cad201ae
Space group (bulk in AA-stacking)	P-3m1
Space group number (bulk in AA-stacking)	164
Point group	-3m
Inversion symmetry	Yes
Layer group number	72
Layer group	p-3m1
2D Bravais type	Hexagonal (hp)
Thickness [Å]	3.824
Structure origin	original03-18
Band gap (PBE) [eV]	0.000

Miscellaneous details
Direct band gap (PBE) [eV]	0.000
gap_dir_nosoc	0.000
Vacuum level [eV]	4.436
Fermi level wrt. vacuum (PBE) [eV]	-3.539
minhessianeig	-13.600
Dynamically stable	No
Interband polarizability (x) [Å]	51.678
Interband polarizability (y) [Å]	51.678
Interband polarizability (z) [Å]	0.472
Plasma frequency (x) [eV Å0.5]	7.803
Plasma frequency (y) [eV Å0.5]	7.803
Energy [eV]	-13.812
Magnetic	No
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]	0.316
Heat of formation [eV/atom]	-0.176