Overview: Al₂Se₄

Structure info
Layer group	c2/m11
Layer group number	18
Structure origin	original03-18

Stability
Energy above convex hull [eV/atom]	0.159
Heat of formation [eV/atom]	-0.555
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	3.072	0.000	0.000	Yes
2	0.000	6.621	0.000	Yes
3	0.000	0.000	18.247	No

Lengths [Å]	3.072	6.621	18.247
Angles [°]	90.000	90.000	90.000

Crystal structure

Symmetries
2D Bravais type	Centered rectangular (oc)
Layer group number	18
Layer group	c2/m11
Space group number (bulk in AA-stacking)	12
Space group (bulk in AA-stacking)	C2/m
Point group	2/m
Inversion symmetry	Yes

Structure data
Formula	Se4Al2
Stoichiometry	AB2
Number of atoms	6
Unit cell area [Å2]	20.343
Thickness [Å]	3.211

Stability

Convex hull

Al2Se4 (2AlSe2-1)
Heat of formation [eV/atom]	-0.55
Energy above convex hull [eV/atom]	0.16

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]

-0.00

Linear deformations

Stiffness tensor

Cij (N/m)	xx	yy	xy
xx	81.94	20.25	-0.02
yy	19.70	91.13	-0.03
xy	0.00	-0.00	57.02

Stiffness tensor eigenvalues
Eigenvalue 0	57.02 N/m
Eigenvalue 1	66.04 N/m
Eigenvalue 2	107.03 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)	-5.556

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Al	2.06
1	Al	2.06
2	Se	-1.03
3	Se	-1.03
4	Se	-1.03
5	Se	-1.03

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	5.240
Interband polarizability (y) [Å]	3.834
Interband polarizability (z) [Å]	0.414
Plasma frequency (x) [eV Å0.5]	2.327
Plasma frequency (y) [eV Å0.5]	15.956

Raman spectrum

Mode	Frequency (1/cm)	Degeneracy
Mode 1	0.1	3
Mode 2	98.	2
Mode 3	104.	1
Mode 4	108.8	1
Mode 5	112.6	1
Mode 6	126.3	1
Mode 7	156.9	1
Mode 8	174.1	2
Mode 9	178.6	1
Mode 10	191.8	1
Mode 11	270.7	1
Mode 12	276.9	1
Mode 13	335.7	1
Mode 14	343.7	1

Miscellaneous

Miscellaneous details
Unique ID	2AlSe2-1
Number of atoms	6
Number of species	2
Formula	Se4Al2
Reduced formula	Se2Al
Stoichiometry	AB2
Unit cell area [Å2]	20.343
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB2/AlSe2/Al2Se4-82f4b5399be7
Old uid	Al2Se4-82f4b5399be7
Space group (bulk in AA-stacking)	C2/m
Space group number (bulk in AA-stacking)	12
Point group	2/m
Inversion symmetry	Yes
Layer group number	18
Layer group	c2/m11
2D Bravais type	Centered rectangular (oc)
Thickness [Å]	3.211
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]	3.888
Fermi level wrt. vacuum (PBE) [eV]	-5.556
minhessianeig	-0.000
Dynamically stable	Yes
Interband polarizability (x) [Å]	5.240
Interband polarizability (y) [Å]	3.834
Interband polarizability (z) [Å]	0.414
Plasma frequency (x) [eV Å0.5]	2.327
Plasma frequency (y) [eV Å0.5]	15.956
Energy [eV]	-24.737
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]	0.159
Heat of formation [eV/atom]	-0.555