Overview: Nb₂Se₂

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

Stability
Energy above convex hull [eV/atom]	0.574
Heat of formation [eV/atom]	-0.231
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	3.218	-0.000	0.000	Yes
2	-1.609	2.787	0.000	Yes
3	-0.000	0.000	21.280	No

Lengths [Å]	3.218	3.218	21.280
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	Nb2Se2
Stoichiometry	AB
Number of atoms	4
Unit cell area [Å2]	8.968
Thickness [Å]	6.305

Stability

Convex hull

Nb2Se2 (2NbSe-5)
Heat of formation [eV/atom]	-0.23
Energy above convex hull [eV/atom]	0.57

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]

-2.84

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	106.17	-17.94	-0.01
yy	-17.79	105.88	-0.01
xy	0.00	0.00	123.67

Stiffness tensor eigenvalues
Eigenvalue 0	88.16 N/m
Eigenvalue 1	123.67 N/m
Eigenvalue 2	123.89 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)	-5.048

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Nb	0.58
1	Nb	0.63
2	Se	-0.61
3	Se	-0.61

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	25.115
Interband polarizability (y) [Å]	25.115
Interband polarizability (z) [Å]	0.763
Plasma frequency (x) [eV Å0.5]	5.863
Plasma frequency (y) [eV Å0.5]	5.863

Miscellaneous

Miscellaneous details
Unique ID	2NbSe-5
Number of atoms	4
Number of species	2
Formula	Nb2Se2
Reduced formula	NbSe
Stoichiometry	AB
Unit cell area [Å2]	8.968
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB/NbSe/Nb2Se2-d3ce7385d21f
Old uid	Nb2Se2-d3ce7385d21f
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]	6.305
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]	5.923
Fermi level wrt. vacuum (PBE) [eV]	-5.048
minhessianeig	-2.836
Dynamically stable	No
Interband polarizability (x) [Å]	25.115
Interband polarizability (y) [Å]	25.115
Interband polarizability (z) [Å]	0.763
Plasma frequency (x) [eV Å0.5]	5.863
Plasma frequency (y) [eV Å0.5]	5.863
Energy [eV]	-28.542
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]	0.574
Heat of formation [eV/atom]	-0.231