| Structure info | |
|---|---|
| Layer group | pm2m |
| Layer group number | 27 |
| Structure origin | exfoliated02-21 |
| ICSD id of parent bulk structure | ICSD 36255 |
| Stability | |
|---|---|
| Energy above convex hull [eV/atom] | 0.000 |
| Heat of formation [eV/atom] | -1.358 |
| Dynamically stable | Yes |
| Basic properties | |
|---|---|
| Magnetic | No |
| Ferroelectric | Yes |
| Band gap (PBE) [eV] | 1.024 |
| Band gap (HSE06) [eV] | 1.845 |
| Symmetries | |
|---|---|
| 2D Bravais type | Rectangular (op) |
| Layer group number | 27 |
| Layer group | pm2m |
| Space group number (bulk in AA-stacking) | 25 |
| Space group (bulk in AA-stacking) | Pmm2 |
| Point group | mm2 |
| Inversion symmetry | No |
| Structure data | |
|---|---|
| Formula | Nb2I4O2 |
| Stoichiometry | ABC2 |
| Number of atoms | 8 |
| Unit cell area [Å2] | 30.086 |
| Thickness [Å] | 4.596 |
| Nb2O2I4 (2NbOI2-1) | |
|---|---|
| Heat of formation [eV/atom] | -1.36 |
| Energy above convex hull [eV/atom] | 0.00 |
| Monolayers from C2DB | |
|---|---|
| Nb4O8 (4NbO2-1) | -2.42 eV/atom |
| Nb2O4 (2NbO2-1) | -2.38 eV/atom |
| NbO2 (1NbO2-1) | -2.37 eV/atom |
| NbO2 (1NbO2-2) | -2.35 eV/atom |
| NbO2 (1NbO2-3) | -2.20 eV/atom |
| Nb4IO7 (1INb4O7-1) | -2.19 eV/atom |
| Nb2I2O4 (2INbO2-1) | -2.09 eV/atom |
| Nb2O6 (2NbO3-1) | -2.07 eV/atom |
| Nb4O12 (4NbO3-1) | -1.83 eV/atom |
| Nb3I2O4 (1I2Nb3O4-1) | -1.75 eV/atom |
| Nb2O2 (2NbO-1) | -1.53 eV/atom |
| Nb2I2O2 (2INbO-1) | -1.39 eV/atom |
| Nb2I4O2, (2NbOI2-1) | -1.36 eV/atom |
| Nb2O2 (2NbO-2) | -1.30 eV/atom |
| Nb2O2 (2NbO-3) | -1.02 eV/atom |
| Nb2I2O (1OI2Nb2-1) | -0.77 eV/atom |
| Nb3I7O (1ONb3I7-1) | -0.74 eV/atom |
| Nb3I8 (1Nb3I8-1) | -0.54 eV/atom |
| Nb2I6 (2NbI3-1) | -0.42 eV/atom |
| Nb2I4 (2NbI2-1) | -0.37 eV/atom |
| Nb2I6 (2NbI3-2) | -0.36 eV/atom |
| NbI2 (1NbI2-1) | -0.18 eV/atom |
| NbI2 (1NbI2-2) | -0.12 eV/atom |
| NbI2 (1NbI2-3) | 0.13 eV/atom |
| Nb2I2 (2INb-1) | 0.14 eV/atom |
| Nb2I2 (2INb-2) | 0.15 eV/atom |
| Minimum eigenvalue of Hessian [eV/Ų] | -0.00 |
| DVB [eV] | xx | yy | xy |
| Γ | -2.04 | 0.05 | -0.04 |
| X | -0.54 | 1.11 | -0.02 |
| S | -0.04 | -0.30 | -0.01 |
| Y | 1.00 | -0.52 | -0.01 |
| kVBM | -2.04 | 0.05 | -0.04 |
| xx | yy | xy | |
| Band gap [eV] | 8.56 | -0.28 | -0.00 |
| DCB [eV] | xx | yy | xy |
| Γ | 9.41 | -2.09 | -0.03 |
| X | -0.94 | -5.40 | -0.05 |
| S | -1.00 | -0.89 | -0.05 |
| Y | 6.52 | -0.23 | -0.04 |
| kCBM | 6.52 | -0.23 | -0.04 |
| Cij (N/m) | xx | yy | xy |
| xx | 66.08 | 5.65 | -0.12 |
| yy | 3.54 | 63.13 | 0.04 |
| xy | -0.00 | 0.01 | 26.21 |
| Stiffness tensor eigenvalues | |
| Eigenvalue 0 | 26.21 N/m |
| Eigenvalue 1 | 59.89 N/m |
| Eigenvalue 2 | 69.31 N/m |
| cij [e/Å] | xx | yy | xy |
| x | -1.33 | 0.03 | -0.00 |
| y | -0.00 | 0.00 | -0.05 |
| z | 0.00 | -0.00 | 0.00 |
| cijclamped [e/Å] | xx | yy | xy |
| x | -0.01 | -0.00 | -0.00 |
| y | 0.00 | 0.00 | -0.02 |
| z | 0.00 | 0.00 | -0.00 |
| Key values [eV] | |
|---|---|
| Band gap (PBE) | 1.024 |
| Direct band gap (PBE) | 1.034 |
| Valence band maximum wrt. vacuum (PBE) | -5.215 |
| Conduction band minimum wrt. vacuum (PBE) | -4.191 |
| Key values [eV] | |
|---|---|
| Band gap (HSE06) | 1.845 |
| Direct band gap (HSE06) | 2.040 |
| Valence band maximum wrt. vacuum (HSE06) | -5.501 |
| Conduction band minimum wrt. vacuum (HSE06) | -3.656 |
| Property (VBM) | Value |
|---|---|
| Min eff. mass | 0.65 m0 |
| Max eff. mass | 1.43 m0 |
| DOS eff. mass | 0.99 m0 |
| Crystal coordinates | [0.000, 0.000] |
| Warping parameter | -0.005 |
| Barrier height | > 19.8 meV |
| Distance to barrier | > 0.0158 Å-1 |
| Property (CBM) | Value |
|---|---|
| Min eff. mass | 0.72 m0 |
| Max eff. mass | 1.00 m0 |
| DOS eff. mass | 0.88 m0 |
| Crystal coordinates | [0.000, 0.496] |
| Warping parameter | 0.002 |
| Barrier height | > 35.5 meV |
| Distance to barrier | > 0.0158 Å-1 |
| ZNbij | ux | uy | uz |
| Px | 6.44 | 0.01 | 0.00 |
| Py | 0.25 | 3.44 | -0.00 |
| Pz | 0.00 | -0.00 | 0.45 |
| ZIij | ux | uy | uz |
| Px | -0.16 | -0.00 | 0.01 |
| Py | -0.00 | -1.65 | -0.00 |
| Pz | 0.01 | 0.00 | -0.11 |
| ZNbij | ux | uy | uz |
| Px | 6.44 | -0.01 | -0.00 |
| Py | -0.25 | 3.44 | -0.00 |
| Pz | -0.00 | -0.00 | 0.45 |
| ZIij | ux | uy | uz |
| Px | -0.16 | 0.00 | -0.01 |
| Py | 0.00 | -1.65 | -0.00 |
| Pz | -0.01 | 0.00 | -0.11 |
| ZOij | ux | uy | uz |
| Px | -6.24 | -0.06 | -0.00 |
| Py | -0.26 | -1.35 | -0.00 |
| Pz | -0.00 | 0.00 | -0.17 |
| ZIij | ux | uy | uz |
| Px | -0.04 | 0.00 | 0.08 |
| Py | 0.00 | -0.44 | 0.00 |
| Pz | 0.02 | -0.00 | -0.17 |
| ZOij | ux | uy | uz |
| Px | -6.24 | 0.06 | 0.00 |
| Py | 0.26 | -1.35 | -0.00 |
| Pz | 0.00 | 0.00 | -0.17 |
| ZIij | ux | uy | uz |
| Px | -0.04 | -0.00 | -0.08 |
| Py | -0.00 | -0.44 | 0.00 |
| Pz | -0.02 | -0.00 | -0.17 |
| Atom No. | Chemical symbol | Charges [|e|] |
|---|---|---|
| 0 | Nb | 1.80 |
| 1 | O | -1.03 |
| 2 | I | -0.41 |
| 3 | I | -0.35 |
| 4 | Nb | 1.78 |
| 5 | O | -1.03 |
| 6 | I | -0.41 |
| 7 | I | -0.35 |
| Spontaneous polarization vector component [pC/m] | |
|---|---|
| Px | -183.061 |
| Py | -0.000 |
| Pz | 0.000 |
| Properties | |
|---|---|
| Interband polarizability (x) [Å] | 2.542 |
| Interband polarizability (y) [Å] | 4.094 |
| Interband polarizability (z) [Å] | 0.458 |
| Static polarizability [Å] | |
|---|---|
| Phonons only (x) | 2.74 |
| Phonons only (y) | 1.84 |
| Phonons only (z) | 0.01 |
| Total (phonons + electrons) (x) | 5.29 |
| Total (phonons + electrons) (y) | 5.93 |
| Total (phonons + electrons) (z) | 0.47 |
| Miscellaneous details | |
|---|---|
| Unique ID | 2NbOI2-1 |
| Number of atoms | 8 |
| Number of species | 3 |
| Formula | Nb2I4O2 |
| Reduced formula | NbI2O |
| Stoichiometry | ABC2 |
| Unit cell area [Å2] | 30.086 |
| Original file-system folder | /home/niflheim2/cmr/C2DB-ASR/ICSD-COD/3el/Nb4I8O4 |
| Old uid | Nb2O2I4-4a99bd580b02 |
| Space group (bulk in AA-stacking) | Pmm2 |
| Space group number (bulk in AA-stacking) | 25 |
| Point group | mm2 |
| Inversion symmetry | No |
| Layer group number | 27 |
| Layer group | pm2m |
| 2D Bravais type | Rectangular (op) |
| Thickness [Å] | 4.596 |
| Structure origin | exfoliated02-21 |
| Band gap (PBE) [eV] | 1.024 |
| Direct band gap (PBE) [eV] | 1.034 |
| gap_dir_nosoc | 1.108 |
| Vacuum level [eV] | 2.049 |
| Fermi level wrt. vacuum (PBE) [eV] | -4.703 |
| Valence band maximum wrt. vacuum (PBE) [eV] | -5.215 |
| Conduction band minimum wrt. vacuum (PBE) [eV] | -4.191 |
| minhessianeig | -0.000 |
| Miscellaneous details | |
|---|---|
| Dynamically stable | Yes |
| Band gap (HSE06) [eV] | 1.845 |
| Direct band gap (HSE06) [eV] | 2.040 |
| Fermi level wrt. vacuum (HSE) [eV] | -4.578 |
| Valence band maximum wrt. vacuum (HSE06) [eV] | -5.501 |
| Conduction band minimum wrt. vacuum (HSE06) [eV] | -3.656 |
| Interband polarizability (x) [Å] | 2.542 |
| Interband polarizability (y) [Å] | 4.094 |
| Interband polarizability (z) [Å] | 0.458 |
| Static polarizability (phonons) (x) [Å] | 2.745 |
| Static polarizability (phonons + electrons) (x) [Å] | 5.287 |
| Static polarizability (phonons) (y) [Å] | 1.840 |
| Static polarizability (phonons + electrons) (y) [Å] | 5.934 |
| Static polarizability (phonons) (z) [Å] | 0.015 |
| Static polarizability (phonons + electrons) (z) [Å] | 0.473 |
| Energy [eV] | -47.682 |
| ICSD id of parent bulk structure | ICSD 36255 |
| Magnetic | No |
| Spin axis | z |
| Magnetic anisotropy energy, xz [meV/unit cell] | 0.000 |
| Magnetic anisotropy energy, yz [meV/unit cell] | 0.000 |
| Ferroelectric | Yes |
| Spontaneous polarization [pC/m] | 183.061 |
| Energy above convex hull [eV/atom] | 0.000 |
| Heat of formation [eV/atom] | -1.358 |
