Overview: Ag₂Se₂

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

Stability
Energy above convex hull [eV/atom]	0.220
Heat of formation [eV/atom]	0.153
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	4.322	-0.000	0.000	Yes
2	-2.161	3.758	0.000	Yes
3	0.000	0.000	18.856	No

Lengths [Å]	4.322	4.335	18.856
Angles [°]	90.000	90.000	119.896

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	Ag2Se2
Stoichiometry	AB
Number of atoms	4
Unit cell area [Å2]	16.242
Thickness [Å]	3.379

Stability

Convex hull

Ag2Se2 (2AgSe-4)
Heat of formation [eV/atom]	0.15
Energy above convex hull [eV/atom]	0.22

Monolayers from C2DB
Se2Ag4 (2SeAg2-1)	-0.09 eV/atom
Se8Ag16 (8SeAg2-1)	-0.07 eV/atom
Ag4Se4 (4AgSe-1)	-0.02 eV/atom
Ag2Se2 (2AgSe-1)	0.02 eV/atom
Ag8Se12 (4Ag2Se3-1)	0.03 eV/atom
Ag2Se4 (2AgSe2-1)	0.05 eV/atom
Ag2Se2 (2AgSe-2)	0.05 eV/atom
Ag2Se2 (2AgSe-3)	0.06 eV/atom
AgSe2 (1AgSe2-1)	0.11 eV/atom
SeAg2 (1SeAg2-1)	0.15 eV/atom
Ag2Se2, (2AgSe-4)	0.15 eV/atom
Ag2Se2 (2AgSe-5)	0.18 eV/atom
Ag2Se4 (2AgSe2-2)	0.19 eV/atom
Se2 (2Se-1)	0.21 eV/atom
AgSe2 (1AgSe2-2)	0.22 eV/atom
Ag2Se2 (2AgSe-6)	0.27 eV/atom
Se2 (2Se-2)	0.29 eV/atom
Ag2 (2Ag-1)	0.31 eV/atom
AgSe2 (1AgSe2-3)	0.32 eV/atom

Bulk crystals from OQMD123
Ag8Se4	-0.07 eV/atom
Ag4	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	20.39	11.23	-0.07
yy	11.01	21.67	0.03
xy	0.11	-0.03	7.20

Stiffness tensor eigenvalues
Eigenvalue 0	7.20 N/m
Eigenvalue 1	9.89 N/m
Eigenvalue 2	32.17 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)	-5.520

Fermi surface

Electronic properties

Bader charges

Atom No.	Chemical symbol	Charges [|e|]
0	Se	-0.29
1	Se	-0.29
2	Ag	0.29
3	Ag	0.29

Optical properties

Optical polarizability

Properties
Interband polarizability (x) [Å]	198.474
Interband polarizability (y) [Å]	518.266
Interband polarizability (z) [Å]	0.434
Plasma frequency (x) [eV Å0.5]	7.774
Plasma frequency (y) [eV Å0.5]	7.801

Raman spectrum

Mode	Frequency (1/cm)	Degeneracy
Mode 1	0.1	3
Mode 2	34.5	2
Mode 3	71.9	1
Mode 4	141.9	1
Mode 5	144.2	1
Mode 6	162.9	2
Mode 7	167.2	2

Miscellaneous

Miscellaneous details
Unique ID	2AgSe-4
Number of atoms	4
Number of species	2
Formula	Ag2Se2
Reduced formula	AgSe
Stoichiometry	AB
Unit cell area [Å2]	16.242
Original file-system folder	/home/niflheim2/cmr/C2DB-ASR/tree/AB/AgSe/Ag2Se2-8b7d07d7fc05
Old uid	Ag2Se2-8b7d07d7fc05
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]	3.379
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]	3.156
Fermi level wrt. vacuum (PBE) [eV]	-5.520
minhessianeig	-0.000
Dynamically stable	Yes
Interband polarizability (x) [Å]	198.474
Interband polarizability (y) [Å]	518.266
Interband polarizability (z) [Å]	0.434
Plasma frequency (x) [eV Å0.5]	7.774
Plasma frequency (y) [eV Å0.5]	7.801
Energy [eV]	-12.033
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]	0.220
Heat of formation [eV/atom]	0.153