Dataset for electronic and optical properties of Y2O2S and Er dopped Y2O2S calculated using density functional theory and simulated x-ray near edge spectra

The computational data presented in this paper refer to the research article “Optical properties and simulated x-ray near edge spectra for Y2O2S and Er doped Y2O2S”. We present the data used to calculate the structural, electronic, and optical properties of the Y2O2S and its Er+3 doped counterparts at various concentrations using density functional theory (DFT) and simulated X-ray near edge (XANES) spectra. We report electronic information from DFT and DFT+U generated from the Vienna Ab initio Simulation Package (VASP) using PAW pseudopotentials. We also report VASP calculated optical properties for the host Y2O2S using the independent particle approximation (IPA), the random phase approximation (RPA), the many-body GW0 approximation, and the Bethe-Salpeter equation (BSE) approximation, under the 10-atom unit cell. The IPA calculations are repeated using the 80-atom unit cell for both the host Y2O2S and the Y2O2S:Er+3 counterparts. The optical properties data include the frequency-dependent real and imaginary parts of the dielectric function, the absorption and extinction coefficients, the refractive index, and the reflectivity. FEFF10 XANES calculations are performed on the Y K-, L1-, L2-, and L3-edges, as well as on the Er M5-edge.

formed on the Y K-, L 1 -, L 2 -, and L 3 -edges, as well as on the Er M 5

Value of the Data
• We provide the data for the structural, electronic, and optical properties of Y 2 O 2 S and Y 2 O 2 S:Er + 3 at various Er concentrations using several computational approaches. These data are useful to experimentalists for predicting the Y 2 O 2 S bandgap and it's change due to Er doping. • We provide calculated X-ray absorption near edge structure (XANES) spectra using the FEFF 10 code, which can be used by experimentalists to analyse transitions in the Y and Er X-ray edges. These data also include projected densities of states per orbital, which are used for electron transition assignments at the X-ray pre-edge and edge regions. • We provide data from different approximations on calculating optical properties, thus showing their accuracy relative to experiments. These data can also be used by computational chemists for further improvement. Our electronic calculations show the presence of the partially filled Er-4f band at the Fermi energy, which agrees with the experimentally observed Er f-f intraband transitions.

Objective
This dataset can be used by computational material scientists to reproduce the electronic and optical properties calculations and explore how the parameters used in the input files affected the calculations' accuracies for Y 2 O 2 S:Er + 3 under varying Er concentrations. Moreover, the Vienna Ab initio Simulation Package (VASP) and FEFF 10 input files contain parameters that can be used for similar calculations of other materials. The data reported for optical properties calculations for the host Y 2 O 2 S refer to different approximations, which affect accuracy, when compared with experimental data. The most accurate approaches for optical properties calculations (i.e., GW and BSE) are not always feasible due to the size of the supercell. In this case, our data show that optical properties calculations using the least accurate IPA method provide sufficiently accurate results relative to the more CPU and memory demanding RPA methods, for energies up to 25 eV. Overall, this dataset adds value to the original published article due to the reproducibility of the data. Fig. 1 shows the geometrically optimized unit cells used in our periodic density functional theory (DFT) [2] and FEFF 10 calculations, as well as the molecular clusters used in our FEFF 10 [3] calculations for the Y 2 O 2 S:Er + 3 under 3.125%, 6.25%, and 9.175% concentrations. The DFT calculations are performed using the 10-atom and 80-atom unit cell. The FEFF 10 calculations for the Y 2 O 2 S:Er + 3 require large clusters, where the absorbing atom is close to the center of the cluster. For the host Y 2 O 2 S, the FEFF calculations use a periodic k-space approach [4] . DFT and DFT + U [5] are used to calculate the Y 2 O 2 S and the Y 2 O 2 S:Er + 3 bandgaps, whereas the manybody GW 0 approximation is also used for the bandgap of the host Y 2 O 2 S:Er + 3 ( Table 1 ). DFT underestimates the bandgaps relative to experiments, whereas DFT + U improves the bandgap value. However, this improvement is fortuitous, since DFT + U alters the conduction band and changes the bandgap from indirect to direct, in contrast with the experiments. The GW 0 overestimates the bandgap, whereas the best agreement is obtained from the BSE approximation. Fig. 2 shows the frequency-dependent dielectric function using GW 0 [ 6 , 7 ] under the independent particle method (IPA) [ 8 , 9 ], the random phase approximation (RPA) [10] , and the BSE [11] approximation. The BSE provides accurate bandgap and excitonic information. The BSE and  Table 1 Bandgaps (E g ) for the Y 2 O 2 S and its Er + 3 doped counterparts per method used.    3 shows the frequency-dependent extinction coefficient κ( ω) for the host Y 2 O 2 S and its Er + 3 doped counterparts under the 80-atom cell. The GW 0 calculations show a shift on the κ( ω) onsite, in agreement with the larger bandgap predicted by GW 0 relative to DFT. The κ( ω) spectrum for the Y 2 O 2 S:Er + 3 at the energies below the bandgap show several peaks, which correspond to the Er f-f intraband transitions. Table 2 shows the static refractive index and reflectivity, as well as the maximum of the refractive index, the reflectivity, and the absorption coefficient, for the host Y 2 O 2 S and its Er doped counterparts. The energy locations for the above maximum values are also given. The denser 8 × 8 × 8 Brillouin zone (BZ) grid does not significantly change the optical properties of the host Y 2 O 2 S. Increased Er doping increases the static refractive index and reflectivity. For the host Y 2 O 2 S, the static values of the refractive index and reflectivity are larger for the IPA and lower for the GW 0 + RPA. Table 3 shows the FEFF calculated X-ray edges of Y and Er, which are com-

Table 2
The static refractive index n(0) and reflectivity R(0) , the maximum values of the refractive index n (ω) max , reflectivity R (ω) max , and absorption coefficient α(ω) max and their locations in the energy spectra per method and unit cell configuration for the host Y 2 O 2 S and its doped counterparts. The energy locations ω are given in parentheses. Values in square brackets refer to the calculations using the -centered 8 × 8 × 8 grid, whereas all other values were obtained using the 6 × 6 × 6 grid.  pared with experimental data. A good agreement between the calculated and the experimentally reported values is obtained for the Y L 2 -and L 3 -edges and the Er L 3 -edge.
The submitted data are grouped in four directories. Three of these four directories contain data which refer to the doped Y 2 O 2 S:Er + 3 compounds at 3.125%, 6.25%, and 9.175% and Er concentrations and are named "Y 2 O 2 S-xEr", where x is 3, 6, and 9. The fourth directory contains data related to the host Y 2 O 2 S. Each of the Y 2 O 2 S-xEr directories contain three subdirectories, where files from FEFF, band structure, and optical properties calculations reside. Moreover, each of the last two directories contain DFT and DFT + U VASP input files and data files that were used for plotting Fig. 3 a. The host Y 2 O 2 S contains three subdirectories, two that contain DFT VASP input files and data files used to plot Fig. 2 and Fig 3 b. These subdirectories are named using the number of atoms in unit cell (i.e., 10-and 80-atom). The last subdirectory contains the host Y 2 O 2 S FEFF files.

Unit cell modeling
The Y 2 O 2 S unit cell in a triclinic form (space group P 3 m1) is used to build 10-and 80-atom supercells in cubic form for Y 2 O 2 S doped with Er + 3 by using the following transformation matrix The unit cell has 5 unique atoms as follows: 2 Y, 2 O, and 1 S atom. The XANES spectra for the Y 2 O 2 S: Er + 3 cases are calculated using 140 atoms clusters of radii ∼ 7.9 Å around the absorbing Er atom.

DFT parameters
We use the periodic DFT code VASP [12][13][14][15] to calculate electronic and optical properties of Y 2 O 2 S and Y 2 O 2 S doped with Er + 3 at 3.175 %, 6.25 %, and 9.375 % Er + 3 concentrations. The VASP PAW pseudopotentials were used [ 16 , 17 ] with Y, O, S, and Er valance electron configurations as 4s 2 4p 6 5s 1 4d 2 , 2s 2 2p 4 , 3s 2 3p 4 , and 5s 2 5p 6 4f 11 5d 1 6s 2 , respectively. The generalized gradient approximation of the Perdew-Burke-Ernzerhof (PBE) functional [18] was used. The longrange electron correlations responsible for van der Waals interactions were approximated by the Grimme [19] D3 semiempirical correction. We used 525 eV for the kinetic energy cutoff for all our calculations, which exceeds the maximum of the default PAW energy cutoff values. The energy SCF convergence and the geometry thresholds are set to 10 −9 eV per atom and 10 −4 eV/ Å , respectively. The BZ was sampled using the 4 × 4 × 4 Monkhorst-Pack grid for geometry optimizations and electronic information, whereas for the optical properties we used the -centered 6 × 6 × 6 BZ grid. The electronic band structure and the densities of states (DOS) are calculated using two district methods: 1) DFT and 2) DFT + U, where U is the Hubbard U correction parameter by Liechtenstein et. al [5] . The optical properties for the host Y 2 O 2 S are calculated using the IPA, the RPA, the many-body GW 0 methods as a correction to IPA and RPA (i.e., GW 0 + IPA and GW 0 + RPA), and the BSE approximation [11] , the last four using the 10-atom unit cell. The Y 2 O 2 S:Er + 3 optical properties were calculated using the IPA method, under the 80-atom unit cell.

FEFF 10 parameters
The FEFF10 code [3] is used to calculate XANES through real space Green functions. The atomic potentials have been calculated self-consistently. We include full multiple scattering in all FEFF 10 calculations. The Hedin-Lundqvist pseudopotential [20] was used for the exchange interaction, whereas the absorbing atom core hole was treated using the RPA method. FEFF also calculates projected DOS per atomic orbital. We used 0.1 eV half-width as the Lorentzian parameter for the projected DOS calculations.

Ethics Statements
This work does not require any ethical statement.

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.