Overview: NbI₂

Structure info
Layer group	p-6m2
Layer group number	78
Structure origin	original03-18

Stability
Energy above convex hull [eV/atom]	0.376
Heat of formation [eV/atom]	-0.116
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	3.631	0.000	0.000	Yes
2	-1.816	3.145	0.000	Yes
3	0.000	0.000	18.955	No

Lengths [Å]	3.631	3.631	18.955
Angles [°]	90.000	90.000	120.000

Crystal structure

Symmetries
2D Bravais type	Hexagonal (hp)
Layer group number	78
Layer group	p-6m2
Space group number (bulk in AA-stacking)	187
Space group (bulk in AA-stacking)	P-6m2
Point group	-6m2
Inversion symmetry	No

Structure data
Formula	NbI2
Stoichiometry	AB2
Number of atoms	3
Unit cell area [Å2]	11.418
Thickness [Å]	3.955

Stability

Convex hull

NbI2 (1NbI2-2)
Heat of formation [eV/atom]	-0.12
Energy above convex hull [eV/atom]	0.38

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]

-8.75

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	61.42	23.68	-0.00
yy	23.69	61.13	-0.00
xy	-0.00	-0.00	39.21

Stiffness tensor eigenvalues
Eigenvalue 0	37.59 N/m
Eigenvalue 1	39.21 N/m
Eigenvalue 2	84.96 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)	-3.211

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Nb	0.94
1	I	-0.47
2	I	-0.47

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	20.682
Interband polarizability (y) [Å]	20.682
Interband polarizability (z) [Å]	0.502
Plasma frequency (x) [eV Å0.5]	5.870
Plasma frequency (y) [eV Å0.5]	5.870

Miscellaneous

Miscellaneous details
Unique ID	1NbI2-2
Number of atoms	3
Number of species	2
Formula	NbI2
Reduced formula	NbI2
Stoichiometry	AB2
Unit cell area [Å2]	11.418
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB2/NbI2/NbI2-147d9f797ecb
Old uid	NbI2-147d9f797ecb
Space group (bulk in AA-stacking)	P-6m2
Space group number (bulk in AA-stacking)	187
Point group	-6m2
Inversion symmetry	No
Layer group number	78
Layer group	p-6m2
2D Bravais type	Hexagonal (hp)
Thickness [Å]	3.955
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]	4.638
Fermi level wrt. vacuum (PBE) [eV]	-3.211
minhessianeig	-8.754
Dynamically stable	No
Interband polarizability (x) [Å]	20.682
Interband polarizability (y) [Å]	20.682
Interband polarizability (z) [Å]	0.502
Plasma frequency (x) [eV Å0.5]	5.870
Plasma frequency (y) [eV Å0.5]	5.870
Energy [eV]	-13.630
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]	0.376
Heat of formation [eV/atom]	-0.116