Overview: Al₂Se₂

Structure info
Layer group	p4/mmm
Layer group number	61
Structure origin	original03-18

Stability
Energy above convex hull [eV/atom]	0.574
Heat of formation [eV/atom]	-0.143
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	5.231	-0.000	0.000	Yes
2	0.000	5.231	0.000	Yes
3	0.000	0.000	15.000	No

Lengths [Å]	5.231	5.231	15.000
Angles [°]	90.000	90.000	90.000

Crystal structure

Symmetries
2D Bravais type	Square (tp)
Layer group number	61
Layer group	p4/mmm
Space group number (bulk in AA-stacking)	123
Space group (bulk in AA-stacking)	P4/mmm
Point group	4/mmm
Inversion symmetry	Yes

Structure data
Formula	Se2Al2
Stoichiometry	AB
Number of atoms	4
Unit cell area [Å2]	27.367
Thickness [Å]	0.000

Stability

Convex hull

Al2Se2 (2AlSe-5)
Heat of formation [eV/atom]	-0.14
Energy above convex hull [eV/atom]	0.57

Monolayers from C2DB
Al8Se12 (4Al2Se3-1)	-0.86 eV/atom
Al4Se6 (2Al2Se3-1)	-0.84 eV/atom
Al4Se6 (2Al2Se3-2)	-0.83 eV/atom
Al4Se6 (2Al2Se3-3)	-0.81 eV/atom
Al2Se3 (1Al2Se3-1)	-0.79 eV/atom
Al6Se9 (3Al2Se3-1)	-0.77 eV/atom
Al2Se3 (1Al2Se3-2)	-0.77 eV/atom
Al3Se4 (1Al3Se4-1)	-0.72 eV/atom
Al2Se2 (2AlSe-1)	-0.72 eV/atom
Al2Se2 (2AlSe-2)	-0.71 eV/atom
Al2Se2 (2AlSe-3)	-0.69 eV/atom
Al2Se5 (1Al2Se5-1)	-0.60 eV/atom
Al2Se4 (2AlSe2-1)	-0.55 eV/atom
AlSe2 (1AlSe2-1)	-0.55 eV/atom
Al2Se2 (2AlSe-4)	-0.36 eV/atom
Al2Se4 (2AlSe2-2)	-0.31 eV/atom
Al2Se2, (2AlSe-5)	-0.14 eV/atom
AlSe4 (1AlSe4-1)	-0.13 eV/atom
Se2 (2Se-1)	0.21 eV/atom
Se2 (2Se-2)	0.29 eV/atom

Bulk crystals from OQMD123
Al4Se6	-0.84 eV/atom
Al	0.00 eV/atom
Se3	0.00 eV/atom

Phonons

Minimum eigenvalue of Hessian [eV/Ų]

-0.25

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	66.16	12.77	0.00
yy	12.77	66.16	0.00
xy	0.00	0.00	29.05

Stiffness tensor eigenvalues
Eigenvalue 0	29.05 N/m
Eigenvalue 1	53.39 N/m
Eigenvalue 2	78.93 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)	-3.493

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Al	1.37
1	Al	1.37
2	Se	-1.37
3	Se	-1.37

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	1.607
Interband polarizability (y) [Å]	1.607
Interband polarizability (z) [Å]	0.223
Plasma frequency (x) [eV Å0.5]	10.456
Plasma frequency (y) [eV Å0.5]	10.456

Miscellaneous

Miscellaneous details
Unique ID	2AlSe-5
Number of atoms	4
Number of species	2
Formula	Se2Al2
Reduced formula	SeAl
Stoichiometry	AB
Unit cell area [Å2]	27.367
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB/AlSe/Al2Se2-abdd54f8c191
Old uid	Al2Se2-abdd54f8c191
Space group (bulk in AA-stacking)	P4/mmm
Space group number (bulk in AA-stacking)	123
Point group	4/mmm
Inversion symmetry	Yes
Layer group number	61
Layer group	p4/mmm
2D Bravais type	Square (tp)
Thickness [Å]	0.000
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]	2.164
Fermi level wrt. vacuum (PBE) [eV]	-3.493
minhessianeig	-0.252
Dynamically stable	No
Interband polarizability (x) [Å]	1.607
Interband polarizability (y) [Å]	1.607
Interband polarizability (z) [Å]	0.223
Plasma frequency (x) [eV Å0.5]	10.456
Plasma frequency (y) [eV Å0.5]	10.456
Energy [eV]	-15.015
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]	-0.143