Overview: Nb₂Se₂

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

Stability
Energy above convex hull [eV/atom]	0.298
Heat of formation [eV/atom]	-0.506
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	4.050	0.000	0.000	Yes
2	-2.025	3.508	0.000	Yes
3	-0.000	0.000	18.856	No

Lengths [Å]	4.050	4.051	18.856
Angles [°]	90.000	90.000	119.995

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	Nb2Se2
Stoichiometry	AB
Number of atoms	4
Unit cell area [Å2]	14.211
Thickness [Å]	3.789

Stability

Convex hull

Nb2Se2 (2NbSe-2)
Heat of formation [eV/atom]	-0.51
Energy above convex hull [eV/atom]	0.30

Monolayers from C2DB
Nb7Se12 (1Nb7Se12-1)	-0.90 eV/atom
Nb8Se12 (4Nb2Se3-1)	-0.88 eV/atom
NbSe2 (1NbSe2-1)	-0.88 eV/atom
Nb4Se6 (2Nb2Se3-1)	-0.87 eV/atom
Nb7Se12 (1Nb7Se12-2)	-0.85 eV/atom
NbSe2 (1NbSe2-2)	-0.85 eV/atom
Nb9Se12 (3Nb3Se4-1)	-0.82 eV/atom
Nb8Se12 (4Nb2Se3-2)	-0.80 eV/atom
Nb9Se12 (3Nb3Se4-2)	-0.75 eV/atom
Nb4Se12 (4NbSe3-1)	-0.70 eV/atom
Nb2Se6 (2NbSe3-1)	-0.67 eV/atom
Se2Nb4 (2SeNb2-1)	-0.55 eV/atom
Nb2Se2 (2NbSe-1)	-0.53 eV/atom
Nb2Se2, (2NbSe-2)	-0.51 eV/atom
Nb2Se2 (2NbSe-3)	-0.46 eV/atom
NbSe2 (1NbSe2-3)	-0.44 eV/atom
Nb2Se2 (2NbSe-4)	-0.25 eV/atom
Nb2Se2 (2NbSe-5)	-0.23 eV/atom
Se2 (2Se-1)	0.21 eV/atom
Se2 (2Se-2)	0.29 eV/atom

Bulk crystals from OQMD123
Nb6Se8	-0.91 eV/atom
Nb4Se8	-0.88 eV/atom
Nb6Se18	-0.69 eV/atom
Nb8Se4	-0.55 eV/atom
Nb4Se18	-0.54 eV/atom
Nb	0.00 eV/atom
Se3	0.00 eV/atom

Phonons

Minimum eigenvalue of Hessian [eV/Ų]

-0.00

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	69.46	65.54	-0.00
yy	65.30	69.31	-0.01
xy	0.00	0.00	5.15

Stiffness tensor eigenvalues
Eigenvalue 0	3.96 N/m
Eigenvalue 1	5.15 N/m
Eigenvalue 2	134.81 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)	-3.986

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Se	-0.88
1	Se	-0.88
2	Nb	0.88
3	Nb	0.88

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	11.578
Interband polarizability (y) [Å]	11.661
Interband polarizability (z) [Å]	0.420
Plasma frequency (x) [eV Å0.5]	5.348
Plasma frequency (y) [eV Å0.5]	5.379

Raman spectrum

Mode	Frequency (1/cm)	Degeneracy
Mode 1	0.	3
Mode 2	93.7	2
Mode 3	189.2	1
Mode 4	233.	2
Mode 5	267.4	1
Mode 6	286.	1
Mode 7	294.3	2

Miscellaneous

Miscellaneous details
Unique ID	2NbSe-2
Number of atoms	4
Number of species	2
Formula	Nb2Se2
Reduced formula	NbSe
Stoichiometry	AB
Unit cell area [Å2]	14.211
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB/NbSe/Nb2Se2-c68c118e4d1a
Old uid	Nb2Se2-c68c118e4d1a
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]	3.789
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]	4.120
Fermi level wrt. vacuum (PBE) [eV]	-3.986
minhessianeig	-0.000
Dynamically stable	Yes
Interband polarizability (x) [Å]	11.578
Interband polarizability (y) [Å]	11.661
Interband polarizability (z) [Å]	0.420
Plasma frequency (x) [eV Å0.5]	5.348
Plasma frequency (y) [eV Å0.5]	5.379
Energy [eV]	-29.643
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]	0.298
Heat of formation [eV/atom]	-0.506