Overview: Nb₂I₄

Structure info
Layer group	p2_1/m11
Layer group number	15
Structure origin	original03-18

Stability
Energy above convex hull [eV/atom]	0.123
Heat of formation [eV/atom]	-0.369
Dynamically stable	Yes

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	3.808	-0.000	0.000	Yes
2	-0.000	6.569	0.000	Yes
3	0.000	0.000	18.824	No

Lengths [Å]	3.808	6.569	18.824
Angles [°]	90.000	90.000	90.000

Crystal structure

Symmetries
2D Bravais type	Rectangular (op)
Layer group number	15
Layer group	p2_1/m11
Space group number (bulk in AA-stacking)	11
Space group (bulk in AA-stacking)	P2_1/m
Point group	2/m
Inversion symmetry	Yes

Structure data
Formula	Nb2I4
Stoichiometry	AB2
Number of atoms	6
Unit cell area [Å2]	25.015
Thickness [Å]	4.243

Stability

Convex hull

Nb2I4 (2NbI2-1)
Heat of formation [eV/atom]	-0.37
Energy above convex hull [eV/atom]	0.12

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]

-0.00

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	50.60	12.76	-0.00
yy	12.80	67.16	-0.00
xy	0.00	0.00	42.50

Stiffness tensor eigenvalues
Eigenvalue 0	42.50 N/m
Eigenvalue 1	43.65 N/m
Eigenvalue 2	74.11 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)	-2.980

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Nb	0.91
1	I	-0.41
2	I	-0.41
3	Nb	0.91
4	I	-0.50
5	I	-0.50

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	6.114
Interband polarizability (y) [Å]	5.629
Interband polarizability (z) [Å]	0.454
Plasma frequency (x) [eV Å0.5]	1.995
Plasma frequency (y) [eV Å0.5]	4.598

Raman spectrum

Mode	Frequency (1/cm)	Degeneracy
Mode 1	0.1	3
Mode 2	54.4	1
Mode 3	60.	1
Mode 4	86.	2
Mode 5	89.8	1
Mode 6	95.4	1
Mode 7	117.4	1
Mode 8	126.3	1
Mode 9	129.6	1
Mode 10	140.5	1
Mode 11	174.3	1
Mode 12	190.5	1
Mode 13	227.6	1
Mode 14	242.	1
Mode 15	246.1	1

Miscellaneous

Miscellaneous details
Unique ID	2NbI2-1
Number of atoms	6
Number of species	2
Formula	Nb2I4
Reduced formula	NbI2
Stoichiometry	AB2
Unit cell area [Å2]	25.015
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB2/NbI2/Nb2I4-198306484fe5
Old uid	Nb2I4-198306484fe5
Space group (bulk in AA-stacking)	P2_1/m
Space group number (bulk in AA-stacking)	11
Point group	2/m
Inversion symmetry	Yes
Layer group number	15
Layer group	p2_1/m11
2D Bravais type	Rectangular (op)
Thickness [Å]	4.243
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]	4.158
Fermi level wrt. vacuum (PBE) [eV]	-2.980
minhessianeig	-0.000
Dynamically stable	Yes
Interband polarizability (x) [Å]	6.114
Interband polarizability (y) [Å]	5.629
Interband polarizability (z) [Å]	0.454
Plasma frequency (x) [eV Å0.5]	1.995
Plasma frequency (y) [eV Å0.5]	4.598
Energy [eV]	-28.783
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]	0.123
Heat of formation [eV/atom]	-0.369