Overview: Nb₂I₂

Structure info
Layer group	c2/m11
Layer group number	18
Structure origin	original03-18

Stability
Energy above convex hull [eV/atom]	0.507
Heat of formation [eV/atom]	0.138
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	3.610	-0.000	0.000	Yes
2	-1.805	4.150	0.000	Yes
3	-0.000	0.000	18.856	No

Lengths [Å]	3.610	4.526	18.856
Angles [°]	90.000	90.000	113.503

Crystal structure

Symmetries
2D Bravais type	Centered rectangular (oc)
Layer group number	18
Layer group	c2/m11
Space group number (bulk in AA-stacking)	12
Space group (bulk in AA-stacking)	C2/m
Point group	2/m
Inversion symmetry	Yes

Structure data
Formula	Nb2I2
Stoichiometry	AB
Number of atoms	4
Unit cell area [Å2]	14.983
Thickness [Å]	4.499

Stability

Convex hull

I2Nb2 (2INb-1)
Heat of formation [eV/atom]	0.14
Energy above convex hull [eV/atom]	0.51

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]

-0.79

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	73.90	25.29	-2.17
yy	26.07	83.25	-3.03
xy	-1.60	-2.47	-28.45

Stiffness tensor eigenvalues
Eigenvalue 0	-28.53 N/m
Eigenvalue 1	52.47 N/m
Eigenvalue 2	104.76 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)	-3.230

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	I	-0.51
1	I	-0.51
2	Nb	0.51
3	Nb	0.51

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	18.034
Interband polarizability (y) [Å]	12.331
Interband polarizability (z) [Å]	0.509
Plasma frequency (x) [eV Å0.5]	3.332
Plasma frequency (y) [eV Å0.5]	3.506

Miscellaneous

Miscellaneous details
Unique ID	2INb-1
Number of atoms	4
Number of species	2
Formula	Nb2I2
Reduced formula	NbI
Stoichiometry	AB
Unit cell area [Å2]	14.983
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB/INb/I2Nb2-c23df32e564b
Old uid	I2Nb2-c23df32e564b
Space group (bulk in AA-stacking)	C2/m
Space group number (bulk in AA-stacking)	12
Point group	2/m
Inversion symmetry	Yes
Layer group number	18
Layer group	c2/m11
2D Bravais type	Centered rectangular (oc)
Thickness [Å]	4.499
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]	4.406
Fermi level wrt. vacuum (PBE) [eV]	-3.230
minhessianeig	-0.792
Dynamically stable	No
Interband polarizability (x) [Å]	18.034
Interband polarizability (y) [Å]	12.331
Interband polarizability (z) [Å]	0.509
Plasma frequency (x) [eV Å0.5]	3.332
Plasma frequency (y) [eV Å0.5]	3.506
Energy [eV]	-23.056
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]	0.507
Heat of formation [eV/atom]	0.138