Overview: Nb₂I₂

Structure info
Layer group	p4/nmm
Layer group number	64
Structure origin	original03-18

Stability
Energy above convex hull [eV/atom]	0.522
Heat of formation [eV/atom]	0.153
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	4.071	-0.000	0.000	Yes
2	0.000	4.071	0.000	Yes
3	0.000	0.000	19.285	No

Lengths [Å]	4.071	4.071	19.285
Angles [°]	90.000	90.000	90.000

Crystal structure

Symmetries
2D Bravais type	Square (tp)
Layer group number	64
Layer group	p4/nmm
Space group number (bulk in AA-stacking)	129
Space group (bulk in AA-stacking)	P4/nmm
Point group	4/mmm
Inversion symmetry	Yes

Structure data
Formula	Nb2I2
Stoichiometry	AB
Number of atoms	4
Unit cell area [Å2]	16.574
Thickness [Å]	3.992

Stability

Convex hull

I2Nb2 (2INb-2)
Heat of formation [eV/atom]	0.15
Energy above convex hull [eV/atom]	0.52

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]

-0.78

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	-9.61	44.06	-0.00
yy	44.06	-9.61	-0.00
xy	0.00	0.00	69.98

Stiffness tensor eigenvalues
Eigenvalue 0	-53.67 N/m
Eigenvalue 1	34.46 N/m
Eigenvalue 2	69.98 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)	-2.561

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

Miscellaneous

Miscellaneous details
Unique ID	2INb-2
Number of atoms	4
Number of species	2
Formula	Nb2I2
Reduced formula	NbI
Stoichiometry	AB
Unit cell area [Å2]	16.574
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB/INb/I2Nb2-a0373ab0dd75
Old uid	I2Nb2-a0373ab0dd75
Space group (bulk in AA-stacking)	P4/nmm
Space group number (bulk in AA-stacking)	129
Point group	4/mmm
Inversion symmetry	Yes
Layer group number	64
Layer group	p4/nmm
2D Bravais type	Square (tp)

Miscellaneous details
Thickness [Å]	3.992
Structure origin	original03-18
Band gap (PBE) [eV]	0.000
Direct band gap (PBE) [eV]	0.000
gap_dir_nosoc	0.000
Vacuum level [eV]	3.884
Fermi level wrt. vacuum (PBE) [eV]	-2.561
minhessianeig	-0.780
Dynamically stable	No
Energy [eV]	-22.996
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]	0.522
Heat of formation [eV/atom]	0.153