PBE Exchange Research Articles

Investigating the physical characteristics of inorganic cubic perovskite CsZnX3 (X = F, Cl, Br, and I): An extensive ab initio study towards potential applications in photovoltaic perovskite devices

CsZnX3 (X = F, Cl, Br, I) cubic perovskite compounds were investigated using Wien2K with PBE and mBJ energy exchange potentials to determine their structural, electronic, optical, thermoelectric, and thermodynamic properties. The results of Phonon vibrational frequency, formation energy, and cohesive energy show thatall compounds arestable. The electronic properties revealed that CsZnF3 has the highest indirect bandgap as an insulator, followed by CsZnCl3 and CsZnBr3, and CsZnI3 has the lowest indirect bandgap. CsZnX3 (X = Cl, Br, I) are classified as p-type semiconductors based on their electronic structure and the positive values of the Seebeck coefficient. High transparency was shown by low visible and infrared absorption. The investigated compounds exhibit high power factor and high figure of merit (ZT), which exceeds 0.7 over the temperature range 300–800 K. As the material’s temperature rises, its lattice heat conductivity decreases in accordance with thermodynamics. However, when the temperature exceeds the Debye temperature, the volume heat capacity matches the Dulong-Petit limits and the experimental results.

First-principles investigations for electronic and thermoelectric properties of XGeF[formula omitted](X = K, Rb): Nonlocal corrections and SCAN insights

In this research work we have studied the electronic band structures, density of states and thermoelectric parameters of fluorine based cubic perovskites KGeF3 and RbGeF3 using PW-LDA, PBE-GGA, SCAN, rVV10 and vdW-DF3 exchange correlation functionals implemented in Quantum ESPRESSO for thermoelectric applications. The lattice constant and bulk modulus of KGeF3 (RbGeF3) is 4.409 (4.407 Å) and 50.8 (51.8 GPa), respectively. KGeF3 has band gap of 1.917eV and RbGeF3 has band gap of 1.982eV with PBE. The band structures of both compounds are consistent to total density of states. The Seebeck coefficient, power factor, electrical and thermal conductivity are studied in a wide range of temperature from 0 to 800K. The detailed study of band gaps and thermoelectric parameters with variety of DFT methods indicates the significance of KGeF3 and RbGeF3 in thermoelectric devices under high temperature.

Investigation of electronic, elastic, dynamical, thermodynamic and thermoelectric properties of Cobalt based half-Heusler compounds

Heusler compounds have attracted remarkable attention from scientists over the year by virtue of their peculiarity and suitability in multi-functional applications. In the current study, the structural, elastic, dynamical, thermodynamic and thermoelectric properties of CoMSb (M = V, Nb and Ta) half-Heusler compounds were computed. Projector augmented-wave (PAW) pseudopotentials with PBE exchange correlation functional have been used to obtain the results for the studied compounds. The computed elastic constants satisfy the general stability condition based on the cubic symmetry and endorse the ductile nature of the compounds. The CoVSb compound is predicted to be ferromagnetic half-metallic compound while CoNbSb and CoTaSb are non-magnetic compounds. The dynamical properties revealed the dynamical stability in CoVSb and CoTaSb compounds while the imaginary frequency observed at W⟶L⟶Γ predicts instability in CoNbSb compound. The thermodynamic properties for the compounds were reported. The thermoelectric properties were calculated based on the results obtained from electronic structure using semi-classical Boltzmann theory. The ductile nature and the figure of merit computed predict CoMSb (M = V, Nb and Ta) are relatively good for thermoelectric application.

A-site cation engineering of cesium and MAPb0.5Sn0.5I3 perovskite: the properties and optoelectronic performance analysis using DFT calculations

Here, the first-principle calculations with the density functional theory calculations with PBE exchange–correlation functional were employed in investigating the effect of Cesium in the properties and optoelectronic performance of MAPb0.5Sn0.5I3 perovskite using A-site cation engineering technique. The control and Cesium based perovskites were generated and computed through CASTEP analysis from Material studio to determine their properties as well as optoelectronic performance. The findings revealed an improved properties of Cesium added perovskite compared to control ones. However, above 15%Cesium, phase separation was seen which declined the quality of the perovskite films. Moreover, simulation results of perovskites added with Cesium to 15% have demonstrated to have an improved optoelectronic performance as well as thermal stability by maintaining about 76% compared to the control which can retain about 39% of their initial power conversion efficiency after 15 days of aging at 85 °C in the ambient condition. This research presents a viable approach to investigate the impact of cation composition tuning on band gap, which can be extended to other perovskites. Additionally, it offers a broad set of design guidelines prior experiments for attaining a targeted band gap and modifying perovskite crystallization to enhance the characteristics, thermal stability, and optoelectronic performance of perovskite solar cells.

Ab initio study of elastic, electronic, and vibrational properties of SnTe and PbTe.

The elastic, electronic, and vibrational properties of the ground state of the rocksalt SnTe and PbTe are investigated. The deduced elastic constants, namely, shear modulus, Young's modulus, and Poisson's ratio are in very good agreement with the experimental and other theoretical data. The electronic band structure and density of states are obtained with and without considering the spin-orbit coupling. The bandgaps of SnTe and PbTe with (without) spin-orbit coupling are 0.11 (0.05) eV and 0.01 (0.78) eV, respectively. The bandgaps with spin-orbit interactions are nearer to experimental data. The hybrid functionals give higher values of bandgaps for both the SnTe and PbTe. In both compounds, the bandgap increases with volume. The valence bandwidths, however, decrease with increasing volume. The vibrational frequencies are found in reasonable agreement with the experiment. The frequencies increase with pressure. In this work, the ab initio calculations of SnTe and PbTe crystals are carried out applying plane wave pseudopotential method using the QUANTUM ESPRESSO package. The PBE exchange and correlation functional based on GGA is considered. The fully relativistic norm-conserving pseudopotentials for Sn, Pb, and Te are used. The self-consistent field calculations are performed over a dense MP net of 18 × 18 × 18k-points. The energy cut-off of 70 Ryd was found sufficient to achieve convergence of 10-6 Ryd in total energy of the crystals.

Strain Dependent Electronic Properties of Hexagonal Monolayer Boron Phosphide with GPAW using GLLB-SC and PBE

The electronic properties of the hexagonal Boron Phosphide (h-BP) monolayer have been investigated by first-principles calculations. The electronic band structure of the h-BP monolayer has been calculated using GPAW with PBE and GLLB-SC exchange correlations (XCs). The energy band gaps of the h-BP monolayer are found to be 0.89 eV and 1.05 eV for PBE and GLLB-SC, respectively. It is shown that GLLB-SC in calculations as XC ensures a more accurate energy band gap than the PBE. As well as the electronic calculations of the unstrained h-BP monolayer, the strain calculations are performed between +5 and -5 %. The strain in the h-BP monolayer changed the energy band gap between 0.78 eV and 1.24 eV for GLLB-SC and between 0.66 eV and 1 eV for PBE. In this applied strain range the studied structure shows the direct band gap semiconductor behavior.

Exploring the electronic transport, magnetic, and optical properties of strongly correlated systems: A numerical analytical continuation approach

The electronic, magnetic and optical properties of the double perovskites Ca2NiOsO6 and Fe-doped derivative were calculated using the full potential linearized augmented plane wave technique through the GGA + U with PBE exchange correlation functionals. The calculations show that both of the systems are half-metallic with Fe-doped system as a ferromagnet, whereas the undoped system shows the ferrimagnetic ordering. Additionally, the study is extended for calculating the Mott parameters through dynamical mean field theory (DMFT) with the maximum entropy model (MEM). It is found that the MIT model parameters (U, [Formula: see text]) for Ca2NiOsO6 and Ca2Fe[Formula: see text]Ni[Formula: see text]OsO6 systems are (5.7[Formula: see text]eV, 6.0[Formula: see text](eV)[Formula: see text]) and (6.0[Formula: see text]eV, 6.0[Formula: see text](eV)[Formula: see text]), respectively. Furthermore, the calculations agree with optical Drude peak analysis. The optical conductivity, reflectivity, absorptivity, ELOSS function, dielectric function refractive index and sum-rule are also explored in relation to the photoinduced behaviors of the materials.

Dissecting the ingredients of optimally tuned range-separated hybrid models for reliable description of non-adiabatic couplings.

Perusing the non-radiative processes requires a reliable prediction of non-adiabatic couplings (NACs) describing the interaction of two Born-Oppenheimer surfaces. In this regard, the development of appropriate and affordable theoretical methods that accurately account for the NAC terms between different excited-states is desirable. In this work, we develop and validate several variants of the optimally tuned range-separated hybrid functionals (OT-RSHs) for investigating NACs and related properties, such as excited states energy gaps and NAC forces, within the time-dependent density functional theory framework. Particular attention is paid to the influence of the underlying density functional approximations (DFAs), the short- and long-range Hartree-Fock (HF) exchange contributions, and the range-separation parameter. Considering several radical cations and sodium-doped ammonia clusters with the available reference data for the NACs and related quantities as the working models, we have evaluated the applicability and accountability of the proposed OT-RSHs. The obtained results unveil that any combination of the ingredients in the proposed models is not proper for describing the NACs, but a particular compromise among the involved parameters is needed to achieve reliable accuracy. Scrutinizing the results of our developed methods, the OT-RSHs based on the PBEPW91, BPW91, and PBE exchange and correlation DFAs, including about 30% HF exchange at the short-range regime, appeared to be the best performers. We also find that the newly developed OT-RSHs with correct asymptotic exchange-correlation potential have superior performances as compared to their standard counterparts with the default parameters and many earlier hybrids with both fixed and interelectronic distance-dependent HF exchange. The recommended OT-RSHs in this study can hopefully be applicable as computationally efficient alternatives to the expensive wave function-based methods for the systems prone to non-adiabatic properties as well as to screen out the novel candidates prior to their challenging synthesis.

Effect of titanium, antimony, and ruthenium doping on tin dioxide adsorption properties. Quantum‐chemical modeling

AbstractThe influence of the composition of oxides supports on the specific electroactive surface area of Pt in the catalysts, the platinum nanoparticles dispersion, and Pt contents in the catalysts was studied. The Sb‐doped SnO2 oxides with various Sb‐doping levels were prepared as a supports of platinum catalysts in polymer electrolyte membrane fuel cells. Density functional theory simulation of Ti, Sb, and Ru doping of tin dioxide and interaction of the doped surfaces with platinum cluster Pt19 have been carried out. All calculations were performed in PBE exchange–correlation functional, with periodic boundary conditions and projector‐augmented waves (PAW) basis set. The calculation results were compared with the experimental data X‐ray diffraction and transmission electron microscopy (TEM). It was shown that Sb doping of tin dioxide (in quantity of less than 10%, that is, the quantity which cannot provoke significant defects of crystal structure of the supports) leads to a significant increase in a number of platinum clusters adsorbed from the colloidal solution onto the supports surface which results to an increase of the platinum cluster interaction with the supports. The calculated and experimental results are in close fit.

A comprehensive DFT study to evaluate the modulation in the band gap, elastic, and optical behaviour of CsPbBr3 under the effect of stress

The computational Generalized Gradient Approximations (GGA) are applied on cubic Cesium Lead Bromide (CsPbBr3) with different stress values of 0, 5, 10, and 15 GPa for a supercell with PBE exchange relationship parameters to study the structural, mechanical, and optoelectronic characteristics. This study aims to determine how stress affects structural and electronic properties, how optical behaviour changes in reaction to electronic change, and how mechanical properties change as a result. The structure remains cubic, and there is no phase shift, but a reduction in the lattice parameters is seen. The reduction in band gap (1.900 eV) is found from 0–15 GPa and zero at 17 GPa. The partial densities of states (PDOS) of bulk CsPbBr3, Cs, Pb, and Br are also calculated. The partial density states PDOS of bulk CsPbBr3 show that in the valence band range, the sharpest observed peak is for d-states, while in the conduction region, the sharpest peak is for p-states and then for s-states. The significant variation in values of absorption, conductivity (imaginary and real), dielectric function (imaginary and real), loss function, reflectivity, and refractive index (imaginary and real) are found by applying stresses of 0, 5, 10, 15 GPa. Using the energy deformation relationship, the elastic constants are computed. From these constants, various mechanical characteristics such as the bulk modulus, shear modulus, Young modulus, and Poisson ratio are derived and discussed. Additionally, it is a good component in optoelectronic devices due to its high refractive index, absorption, reflectivity, and conductivity.

Magnetic ground state of plutonium dioxide: DFT+U calculations

The magnetic states of the strongly correlated system plutonium dioxide (PuO2) are studied based on the density functional theory (DFT) plus Hubbard U (DFT+U) method with spin–orbit coupling (SOC) included. A series of typical magnetic structures including the multiple-k types are simulated and compared in the aspect of atomic structure and total energy. We test LDA, PBE, and SCAN exchange–correlation functionals on PuO2 and a longitudinal 3k antiferromagnetic (AFM) ground state is theoretically determined. This magnetic structure has been identified to be the most stable one by the former computational work using the hybrid functional. Our DFT+U + SOC calculations for the longitudinal 3k AFM ground state suggest a direct gap which is in good agreement with the experimental value. In addition, a genetic algorithm is employed and proved to be effective in predicting magnetic ground state of PuO2. Finally, a comparison between the results of two extensively used DFT+U approaches to this system is made.

First principles study of adsorption and simulation of desorption properties of [formula omitted] surface alloy

The FCC structure of Pd1−xAgx (x= 0.25, 0.50, 0.75) alloys is considered as a fuel cell component in this study. We have looked into its qualities as a component of a fuel cell to see whether it could be potentially used as an alternative replacement of the Pt catalyst. We used Density Functional Theory (DFT) to study H and CO interaction with the surface, and simulation of desorption process to study H and CO desorption from the surface. The bulk modulus and equilibrium crystal structures of Pd1−xAgx alloys were computed using the GPAW code within plane wave basis set & a PBE exchange correlation functional treatment. The best values of lattice constant for the system are obtained by total energy calculations versus lattice cell volumes as fitted to the stabilized jellium model. Surface energies, cohesive energies, and binding energy of Pd1−xAgx alloys were computed to analyze the stability properties of structures. Band structure calculations, density of states (DOS), and projected density of states (PDOS) reveal the electronic properties as well as the availability of the eigenstates for occupation. The desorption process is simulated based on the Arrhenius type desorption rate & a temperature programming. The effects of lateral interactions between adsorbed molecules is taken into account while analyzing first & second order desorption. The outcomes show good qualitative agreement with literature.

Thermodynamic and optoelectronic properties of GaAs[formula omitted]M[formula omitted] (M [formula omitted] Fe,Cu) ternary compounds via first principles

The electronic structure, band structure and optical properties of compounds GaAs(1−x)Mx (M = Fe,Cu), for x=0.25, 0.75, and 1 are discussed via Full-potential linearized augmented plane wave calculations. An increase in absorption in the visible spectrum is observed for all compounds, which, however, is associated with an increasingly metallic character as the metal concentration increases, to the point that compound GaFe is an indirect degenerate semiconductor. The addition of Fe and Cu to the compound decreases its stability, as demonstrated by the formation enthalpies, which become progressively more positive as the content in As is decreased. The calculations were performed using both the PBE and PBEsol exchange correlation potentials and the TB-mBJ method was used to verify the band structure obtained.

First principles study on organic cation A-site doping in CsPbI3 perovskite

Among all inorganic perovskite, CsPbI3 has the closest ideal bang gap for solar cells. However, the instability of metal halides hinders its commercial application. The doping of A-site organic cations might improve the stability of perovskite and also make the bandgap adjustable, thus enhance its photoelectric properties. In this paper, the structure stability, electronic structure and optical properties of CsPbI3 with five different organic cations (H3NNH2+, CH3NH3+, C3H6NH2+, CH3NH2CH3+, CH3CH2NH3+) partially alternative doping instead the A site cation have been studied by using the first principles within density functional theory. In order to get accurate description of the bandstructure information, different exchange–correlation functions, e. g. PBE, PBE + SOC and HSE were used to describe the calculated systems, our calculation results indicated that the PBE exchange–correlation function can describe the electronic properties of the systems very well in this paper. Formation energy calculation indicates that all the doping systems are thermally stable; and all the doped CsPbI3 show good tolerance factor according Goldschmidt rule. Among the five different doping systems, the bandgap of doped H3NNH2+ will decrease to 1.28 eV, while the bandstructure of other doped cations will widen the bandgap. The maximum bandgap increased to 1.65 eV with doping C3H6NH2+. However, all the band structures are mainly contributed by inorganic framework. The results suggest that the structure doped organic cations can be exited stably, and the band edge of the optical absorption spectrum will be redshifted. These properties can provide research ideas for the subsequent research of A-site doping organic cations.

First-principles investigation of structural, electronic and optical properties of quasi-one-dimensional barium cadmium chalcogenides Ba2CdX3 (X = S, Se, Te) using HSE06 and GGA-PBE functionals

Structural, electronic and optical properties of quasi-one-dimensional barium cadmium chalcogenides Ba2CdS3, Ba2CdSe3 and Ba2CdTe3 are studied using density functional theory. Structural properties of these materials are investigated by incorporating Van der Waals correction with PBE exchange correlation functional. Results of structural analysis are in good agreement with the previously reported experimental observations and confirm the quasi-one-dimensional structure of the compounds. Ba2CdX3 chalcogenide structures crystallize in orthorhombic phase with space group Pnma-D2h16. Band structure calculations with HSE06 show that Ba2CdSe3 and Ba2CdTe3 are wide bandgap materials with direct bandgap of 2.56 eV for Ba2CdSe3 and 2.16 eV for Ba2CdTe3. Ba2CdS3 is an insulator with direct bandgap 3.16 eV. Optical properties are investigated by calculating the refractive index, birefringence, dichroism, dielectric function and absorption coefficient using the HSE06 method. Ba2CdX3 materials exhibit large optical anisotropy with considerable birefringence and dichroism. The comparatively high values of absorption coefficients, extinction coefficients, birefringence and dichroism make Ba2CdX3 materials suitable for applications as polarizers and sensing devices, while the large direct bandgaps indicate that they are promising candidates in photovoltaic applications.

Promising Versions of Non-Zero Magnetic Field Optical Sensors for Magnetoencephalography

Among all inorganic perovskite, CsPbI3 has the closest ideal bang gap for solar cells. However, the instability of metal halides hinders its commercial application. The doping of A-site organic cations might improve the stability of perovskite and also make the bandgap adjustable, thus enhance its photoelectric properties. In this paper, the structure stability, electronic structure and optical properties of CsPbI3 with five different organic cations (H3NNH2+, CH3NH3+, C3H6NH2+, CH3NH2CH3+, CH3CH2NH3+) partially alternative doping instead the A site cation have been studied by using the first principles within density functional theory. In order to get accurate description of the bandstructure information, different exchange–correlation functions, e. g. PBE, PBE + SOC and HSE were used to describe the calculated systems, our calculation results indicated that the PBE exchange–correlation function can describe the electronic properties of the systems very well in this paper. Formation energy calculation indicates that all the doping systems are thermally stable; and all the doped CsPbI3 show good tolerance factor according Goldschmidt rule. Among the five different doping systems, the bandgap of doped H3NNH2+ will decrease to 1.28 eV, while the bandstructure of other doped cations will widen the bandgap. The maximum bandgap increased to 1.65 eV with doping C3H6NH2+. However, all the band structures are mainly contributed by inorganic framework. The results suggest that the structure doped organic cations can be exited stably, and the band edge of the optical absorption spectrum will be redshifted. These properties can provide research ideas for the subsequent research of A-site doping organic cations.

Time-Dependent Long-Range-Corrected Double-Hybrid Density Functionals with Spin-Component and Spin-Opposite Scaling: A Comprehensive Analysis of Singlet-Singlet and Singlet-Triplet Excitation Energies.

Following the work on spin-component and spin-opposite scaled (SCS/SOS) global double hybrids for singlet-singlet excitations by Schwabe and Goerigk [ J. Chem. Theory Comput. 2017, 13, 4307-4323] and our own works on new long-range corrected (LC) double hybrids for singlet-singlet and singlet-triplet excitations [ J. Chem. Theory Comput. 2019, 15, 4735-4744 and J. Chem. Phys. 2020, 153, 064106], we present new LC double hybrids with SCS/SOS that demonstrate further improvement over previously published results and methods. We introduce new unscaled and scaled versions of different global and LC double hybrids based on Becke88 or PBE exchange combined with LYP, PBE, or P86 correlation. For singlet-singlet excitations, we cross-validate them on six benchmark sets that cover small to medium-sized chromophores with different excitation types (local-valence, Rydberg, and charge transfer). For singlet-triplet excitations, we perform the cross-validation on three different benchmark sets following the same analysis as in our previous work in 2020. In total, 203 excitations are analyzed. Our results confirm and extend those of Schwabe and Goerigk regarding the superior performance of SCS and SOS variants compared to their unscaled parents by decreasing mean absolute deviations, root-mean-square deviations, or error spans by more than half and bringing absolute mean deviations closer to zero. Our SCS/SOS variants are shown to be highly efficient and robust for the computation of vertical excitation energies, which even outperform specialized double hybrids that also contain an LC in their perturbative part. In particular, our new SCS/SOS-ωPBEPP86 and SCS/SOS-ωB88PP86 functionals are four of the most accurate and robust methods tested in this work, and we fully recommend them for future applications. However, if the relevant SCS and SOS algorithms are not available to the user, we suggest ωPBEPP86 as the best unscaled method in this work.

Amino acids adsorption onto the (111) surface of cubic zirconia: a density functional theory study

The adsorption of six amino acids onto (111) surface of cubic ZrO2 was theoretically investigated using density functional theory (DFT). DFT calculations with D3 dispersion correction were carried out with the PBE exchange–correlation functional. Mechanism, molecular adsorption structures, and energies were calculated. The (111) surface of cubic ZrO2 was modeled using a slab with 9 atomic layers (81 atoms). The slab thickness was 7.3 A, and a vacuum separation of 12 A was used with periodic boundary conditions. The results showed that the order of the molecular adsorption energies is ASP > HYP > GLY > ALA > LYS > PRO. Furthermore, adsorption of amino acids on the zirconia surface showed complete hydrogen transfer from GLY, ALA, HYP, and ASP to the surface. For LYS and PRO, hydrogen transfer does not occur. Topological analysis of the electron localization function (ELF) was applied to study the nature of the molecule-surface interactions. It was found that the dissociation of molecules and strong chemical bonds of adsorbed atoms to surface oxygen atoms play an important role in the adsorption mechanism.

Theoretical study of the structures and electronic properties for NiX (X = Na–Cl) clusters

Using the first-principles calculations, we study the structural, electronic and magnetic properties of the neutral and ionic Nin-1X (n = 19–23; X = Na–Cl) clusters. The calculations are performed using the density functional theory with the PBE exchange–correlation energy functional. The results reveal that the most stable structures of Nin-1X (X = Na, Mg, Al, Si) clusters are all similar to those of corresponding Nin clusters, while there are substantial structural deformations of Nin-1X (X = P, S, Cl) clusters. From the optimized results, a systematic analysis is carried out to obtain the relative stability, charge transfer, magnetic moments, density of states, electron affinity and ionization potential of Nin-1X clusters. Our findings also suggest how to change the stability, electronic and magnetic properties by doping different atoms in Ni clusters.

Theoretical study of the adsorption of diphenylalanine on pristine graphene

We perform density functional theory calculations to investigate the adsorption properties of diphenylalanine on pristine graphene. We use PBE exchange–correlation functional with corrections for van der Waals interactions (PBE-D3) during the calculations. The formation of the diphenylalanine/graphene complexes is favourable energetically in all cases. The well-known pristine graphene’s semi-metallic nature is modified when the diphenylalanine molecule adsorbs. One can observe, through the analysis of the adsorption energy, that the strongest interaction is the one in which diphenylalanine adsorbs on graphene through offset aromatic interactions. The results obtained here can provide useful guidance in designing novel hybrid organic/inorganic materials for many biomedical applications.