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The structure-property relationship of diarylethene (DAE)-derivative molecular isomers, which involve ring-closed and ring-open forms, is investigated by employing the non-equilibrium Green’s function formalism combined with density functional theory. Molecular junctions are formed by the isomers connecting to Au(111) electrodes through flanked pyridine groups. The difference in electronic structures caused by different geometry structures for the two isomers, particularly the interatomic alternative single bond and double bond of the ring-closed molecule, contributes to the vastly different low-bias conductance values. The lowest unoccupied molecular orbital (LUMO) of the isomers is the main channel for electron transport. In addition, more electrons transferred to the ring-closed molecular junction in the equilibrium condition, thereby decreasing the LUMO energy to near the Fermi energy, which may contribute to a larger conductance value at the Fermi level. Our findings are helpful for understanding the mechanism of low-bias conductance and are conducive to the design of high-performance molecular switching based on diarylethene or diarylethene-derivative molecules.

Reactions of gas-phase species with small molecules are being actively studied to understand the elementary steps and mechanistic details of related condensed-phase processes. Activation of the very inert N≡N triple bond of dinitrogen molecule by isolated gas-phase species has attracted considerable interest in the past few decades. Apart from molecular adsorption and dissociative adsorption, interesting processes such as C-N coupling and degenerate ligand exchange were discovered. The present review focuses on the recent progress on adsorption, activation, and functionalization of N2 by gas-phase species (particularly metal cluster ions) using mass spectrometry, infrared photo-dissociation spectroscopy, anion photoelectron spectroscopy, and quantum chemical calculations including density functional theory and high-level ab initio calculations. Recent advances including characterization of adsorption products, dependence of clusters’ reactivity on their sizes and structures, and mechanisms of N≡N weakening and splitting have been emphasized and prospects have been discussed.

The simple homodinuclear M-M single bonds for group II and XII elements are difficult to obtain as a result of the fulfilled s2 electronic configurations, consequently, a dicationic prototype is often utilized to design the M+ −M+ single bond. Existing studies generally use sterically bulky organic ligands L− to synthesize the compounds in the L− −M+ −M+ −L− manner. However, here we report the design of Mg-Mg and Zn-Zn single bonds in two ligandless clusters, Mg2B7− and Zn2B7−, using density functional theory methods. The global minima of both of the clusters are in the form of M22+(B73−), where the M-M single bonds are positioned above a quasi-planar hexagonal B7 moiety. Chemical bonding analyses further confirm the existence of Mg-Mg and Zn-Zn single bonds in these clusters, which are driven by the unusually stable B73− moiety that is both σ and π aromatic. Vertical detachment energies of Mg2B7− and Zn2B7− are calculated to be 2.79 eV and 2.94 eV, respectively, for the future comparisons with experimental data.

The binding energy and generalized stacking-fault energy (GSFE) are two critical interface properties of two dimensional layered materials, and it is still unclear how neighboring layers affect the interface energy of adjacent layers. Here, we investigate the effect of neighboring layers by comparing the differences of binding energy and GSFE between trilayer heterostructures (graphene/graphene/graphene, graphene/graphene/boron nitride, boron nitride/graphene/boron nitride) and bilayer heterostructures (graphene/graphene, graphene/boron nitride) using density functional theory. The binding energy of the adjacent layers changes from -2.3% to 22.55% due to the effect of neighboring layer, with a very small change of the interlayer distance. Neighboring layers also make a change from -2% to 10% change the GSFE, depending on the property of the interface between adjacent layers. In addition, a new simple expression is proven to describe the GSFE landscape of graphene-like structure with high accuracy.

The thermodynamic stability and lithiated/delithiated potentials of LiFe $_x$ Mn $_{1-x}$ PO $_4$ were studied with density functional theorical calculations. The results show that the formation free energy of the LiFe $_x$ Mn $_{1-x}$ PO $_4$ solid solution is slightly higher than that of the phase-separated mixture of LiFePO $_4$ and LiMnPO $_4$ , and the two forms may co-exist in the actual LiFe $_x$ Mn $_{1-x}$ PO $_4$ materials. The calculation manifests that the lithiated/delithiated potentials of LiFe $_x$ Mn $_{1-x}$ PO $_4$ solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFe $_x$ Mn $_{1-x}$ PO $_4$ materials by solid-phase reaction method. The existence of the LiFe $_x$ Mn $_{1-x}$ PO $_4$ solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.

Raman spectra of 1, 2, 4-triazole-3-carboxylate (TC $^-$ anion) and its ring-deprotonated derivative (dpTC $^{2-}$ dianion) in aqueous solutions were measured respectively. The density functional theory calculations were performed using MN15 functional and PCM solvent model to investigate their structures, as well as the vibrational frequencies and Raman intensities. With the aid of the calculated spectra, all the observed Raman bands of dpTC $^{2-}$ were clearly assigned, with taking into account the deuteration shifts. Moreover, various protonic tautomers of TC $^-$ anion were compared in the present theoretical calculations, and 2H-tautomer was found more stable. The experimental Raman spectrum of TC $^-$ solution was roughly consistent with the calculated spectrum of the monomeric 2H-tautomer of TC $^-$ , but some splits existed for a few bands when compared to the calculated spectra, which might be contributed by the hydrogen-bonding dimers of TC $^-$ .

Better ways are needed to capture radioactive volatile fission products (Kr, Xe, Br, I, Te, Rb, and Cs) discharged during the reprocessing of spent nuclear fuel in order to reduce the volumes of produced waste and minimize environmental impact. Using density functional theory, we examine the efficacy of a one-dimensional yttrium silicide electride (Y5Si3:e−) as a host matrix to encapsulate these species. Endoergic encapsulation energies calculated for Kr, Xe, Rb, and Cs imply they are not captured by Y5Si3:e−. Encapsulation is exoergic for Br, I, and Te with respect to their atoms and dimers as reference states, meaning that they can be captured effectively due to their high electronegativities. This is further supported by the formation of anions due to charge transfer between Y5Si3:e− and Br (I and Te). The selectivity of this material for these volatile species makes it promising for use in nuclear filters.

In this work, the optical properties of fluorescent probes used for detection of biothiol were studied by employing time-dependent density functional theory. By calculating the single photon absorption and emission properties of probe Mol.1, Mol.2 and Mol.3 before and after reaction with cysteine and homocysteine, we have investigated the effect of carbon-carbon triple bond and benzene ring on the properties of fluorescent probes. It is found that the oscillator strength of probe molecules increases gradually with the improvement of the structure of the electron donor triphenylamine and the addition of carbon-carbon triple bonds, and better properties of fluorescence probes have also been demonstrated. At the same time, the effect of different number of side branches on the molecular properties of the probe was also studied. The results showed that compared with single-branched molecule Z1 and tribranched probe Mol.3, two side probe molecules Z2 had higher oscillator strength and better detection effect. In addition, the new single-branched probe Mol.4 with the addition of carbon-carbon triple bonds and benzene rings has better probe properties and simpler structure than the tribranched probe Mol.3.

Accurate description of the adsorption process of reactants on metal surfaces from theory is crucial for mechanistic understanding of activity and selectivity of metal catalysts, but it remains challengeable for the nowadays first-principles theory due to the lack of proper exchange-correlation functional describing the distinct interactions involved. We studied here the potential energy surfaces of ethylene adsorption on Ag(111), Rh(111) and Ir(111) using density functional theory calculations and (meta)-GGA functional including PBE, BEEF-vdW, SCAN, and SCAN+rVV10. For ethylene adsorption on noble metal Ag(111), it is found that BEEF-vdW, SCAN and SCAN+rVV10 predict the presence of the physisorption states only. For Rh(111), both SCAN and SCAN+rVV10 find that there is a precursor physisorption state before the chemisorption state. In contrast, there is no precursor state found based on potential energy surfaces from BEEF-vdW and PBE. Whereas for Ir(111), BEEF-vdW predicts the existence of a rather shallow precursor physisorption state, in addition to the chemisorption state. Irrespective to the transition metals considered, we find that SCAN+rVV10 gives the strongest binding strength, followed by SCAN, and PBE/BEEF-vdW, accordingly. The present work highlights great dependence of potential energy surface of ethylene adsorption on transition metal surfaces and exchange-correlation functionals.

Here an electron momentum spectroscopy study on the electronic structure of valence shell of iso-dichloroethylene molecule is reported. The experiment is carried out with a binary (e, 2e) spectrometer at incident electron energy of 1200 eV, employing noncoplanar symmetric arrangement. The binding energy spectra and electron momentum distributions (EMDs) of iso-dichloroethylene valence shell have been obtained. Theoretical EMDs are predicted with both Hartree-Fock and density functional theory methods, generally indicating good agreements with the measurement results. The interference effect is observed to significantly influence the EMDs of 2a2 and 5b2 Cl lone-pair orbitals.

MgH $_2$ is a promising and popular hydrogen storage material. In this work, the hydrogen desorption reactions of a single Pd atom adsorbed MgH $_2$ (110) surface are investigated by using first-principles density functional theory calculations. We find that a single Pd atom adsorbed on the MgH $_2$ (110) surface can significantly lower the energy barrier of the hydrogen desorption reactions from 1.802 eV for pure MgH $_2$ (110) surface to 1.154 eV for Pd adsorbed MgH $_2$ (110) surface, indicating a strong Pd single-atom catalytic effect on the hydrogen desorption reactions. Furthermore, the Pd single-atom catalysis significantly reduces the hydrogen desorption temperature from 573 K to 367 K, which makes the hydrogen desorption reactions occur more easily and quickly on the MgH $_2$ (110) surface. We also discuss the microscopic process of the hydrogen desorption reactions through the reverse process of hydrogen spillover mechanism on the MgH $_2$ (110) surface. This study shows that Pd/MgH $_2$ thin films can be used as good hydrogen storage materials in future experiments.

It is a challenge to recover lithium from the leaching solution of spent lithium-ion batteries, and crown ethers are potential extractants due to their selectivity to alkali metal ions. The theoretical calculations for the selectivity of crown ethers with different structures to Li ions in aqueous solutions were carried out based on the density functional theory. The calculated results of geometries, binding energies, and thermodynamic parameters show that 15C5 has the strongest selectivity to Li ions in the three crown ethers of 12C4, 15C5, and 18C6. B15C5 has a smaller binding energy but more negative free energy than 15C5 when combined with Li $^+$ , leading to that the lithium ions in aqueous solutions will combine with B15C5 rather than 15C5. The exchange reactions between B15C5 and hydrated Li $^+$ , Co $^{2+}$ , and Ni $^{2+}$ were analyzed and the results show that B15C5 is more likely to capture Li $^+$ from the hydrated ions in an aqueous solution containing Li $^+$ , Co $^{2+}$ , and Ni $^{2+}$ . This study indicates that it is feasible to extract Li ions selectively using B15C5 as an extractant from the leaching solution of spent lithium-ion batteries.

Based on density functional theory calculations, the full hydrolysis of per N $\rm{H}_\rm{3}$ B $\rm{H}_\rm{3}$ molecule to produce three hydrogen molecules on single Pt atoms supported on oxidized graphene (P $\rm{t}_{1}$ /Gr-O) is investigated. It is suggested that the first hydrogen molecule is produced by the combination of two hydrogen atoms from two successive B-H bonds breaking. Then one $\rm{H}_\rm{2}$ O molecule attacks the left $^*$ BHN $\rm{H}_\rm{3}$ group ( $^*$ represents adsorbed state) to form $^*$ BH( $\rm{H}_\rm{2}$ O)N $\rm{H}_\rm{3}$ and the elongated O-H bond is easily broken to produce $^*$ BH(OH)N $\rm{H}_\rm{3}$ . The second $\rm{H}_\rm{2}$ O molecule attacks $^*$ BH(OH)N $\rm{H}_\rm{3}$ to form $^*$ BH(OH)( $\rm{H}_\rm{2}$ O)N $\rm{H}_\rm{3}$ and the breaking of O-H bond pointing to the plane of P $\rm{t}_{1}$ /Gr-O results in the desorption of BH $\rm{(OH)}_\rm{2}$ N $\rm{H}_\rm{3}$ . The second hydrogen molecule is produced from two hydrogen atoms coming from two $\rm{H}_\rm{2}$ O molecules and P $\rm{t}_{1}$ /Gr-O is recovered after the releasing of hydrogen molecule. The third hydrogen molecule is generated by the further hydrolysis of BH $\rm{(OH)}_\rm{2}$ N $\rm{H}_\rm{3}$ in water solution. The rate-limiting step of the whole process is the combination of one $\rm{H}_\rm{2}$ O molecule and $^*$ BHN $\rm{H}_\rm{3}$ with an energy barrier of 16.1 kcal/mol. Thus, P $\rm{t}_{1}$ /Gr-O is suggested to be a promising catalyst for hydrolysis of N $\rm{H}_\rm{3}$ B $\rm{H}_\rm{3}$ at room temperature.

Structural, electronic and optical properties of concentration dependent indium (In) doped ZnO monolayer are studied in the framework of density functional theory. We have considered the various concentration of In (6.25, 12.50 and 18.75 atomic (at.) %) in ZnO monolayer. We have used Vienna Ab initio Simulation Package (VASP) with Projected Augmented Wave (PAW) pseudopotentials and generalized gradient approximation - Perdew, Burke and Ernzerhof (GGA-PBE) functional. Substitution of Zn with In atom is energetically favorable. The large sized In atom as compared to that of Zn induces the stress in ZnO monolayer. To reduce the stress, In atom protrudes out from the plane of ZnO monolayer. The computational model under DFT calculations with ultrasoft pseudopotential and PBE exchange correlation functional, showed that In atom remains in the plane of ZnO monolayer. Similar behavior is observed with the use of full-potential linearized augmented plane wave (FLAPW)-GGA approach. The effects of pseudopotential and exchange correlation functional are observed in terms of structural deformation in In-doped ZnO monolayer. It effectively modulates the band structure and optical properties. The computational codes, potentials, and exchange correlation functionals are playing major role in investigating the structural and electronic properties of various nanostructures.

The efficient capture of volatile fission products released during spent fuel reprocessing is a crucial concern for the nuclear community. Here, we apply the density functional theory to examine the efficacy of a two-dimensional dicalcium nitride electride (Ca2N:ē) to encapsulate volatile fission products. Encapsulation is endoergic for Kr, Xe, Rb, and Cs meaning that they are not encapsulated. Conversely, strong encapsulation is exhibited for Br, I, and Te with respect to their atoms and dimers as reference states. The preference for Br, I, and Te encapsulation is a consequence of charge transfer from Ca2N:ē to form encapsulated anions. This makes the electride a promising material for the selective trapping of volatile Br, I, and Te.

The structures and vibrational spectra of biologically active molecules of 5-chlorouracil (5CU) in various states were studied. The IR Fourier spectra of 5CU molecules isolated in the low-temperature Ar and Ne matrices were obtained in the infrared range of 3800–500 cm–1. The populations of 5CU tautomers were estimated, and vibrational spectra were calculated using the DFT/B3LYP method with a basis of 6-311++G(df,pd). In the Ar matrix, 7 Raman modes of 5CU amplified by Fermi resonance were detected in the spectral range of 1900–500 cm–1. In the region of fundamental vibrations νCO and in the vibration region of the ring, triple Fermi resonances were observed. Thin 5CU films on the surface of graphene oxide (GO) and composite films 5CU/GO obtained from an aqueous solution were grown and investigated at cryogenic temperatures. It was shown that, as the temperature rises from the helium temperature to room temperature, the 5CU film crystallizes on the GO surface. Comparison of the spectra of the 5CU films obtained enabled identification of vibrations whose absorption bands were most sensitive to changes in the crystal structure of the film. Most of these fundamental modes were associated with vibrations of the NH group. With an increase in the concentration of 5CU in the 5CU/GO composite films, a nonuniform distribution of the 5CU micro-crystals over the sample area was observed.The structures and vibrational spectra of biologically active molecules of 5-chlorouracil (5CU) in various states were studied. The IR Fourier spectra of 5CU molecules isolated in the low-temperature Ar and Ne matrices were obtained in the infrared range of 3800–500 cm–1. The populations of 5CU tautomers were estimated, and vibrational spectra were calculated using the DFT/B3LYP method with a basis of 6-311++G(df,pd). In the Ar matrix, 7 Raman modes of 5CU amplified by Fermi resonance were detected in the spectral range of 1900–500 cm–1. In the region of fundamental vibrations νCO and in the vibration region of the ring, triple Fermi resonances were observed. Thin 5CU films on the surface of graphene oxide (GO) and composite films 5CU/GO obtained from an aqueous solution were grown and investigated at cryogenic temperatures. It was shown that, as the temperature rises from the helium temperature to room t...

Based on the experimental study of the optical properties of K2Ti6O13 doped with Fe or Ag, their electronic structures and optical properties are studied by the first-principles method based on the density functional theory (DFT). The calculated optical properties are consistent with the experiment results. K2Ti6O13 doped with substitutional Fe or Ag has isolated impurity bands mainly stemming from the hybridization by the Fe 3d states or Ag 4d states with Ti 3d states and O 2p states and the band gap becomes narrower, the absorption edge of K2Ti6O13 thus has a clear red shift and the absorption of visible light can be realized after doping. For Fe-doped K2Ti6O13, the impurity bands are in the middle of the band gap, suggesting that they can be used as a bridge for valence band electrons transition to the conduction band. For Ag-doped K2Ti6O13, the impurity bands form a shallow acceptor above the valence band and can reduce the recombination rate of photoexcited carriers. The experimental and calculated results are significant for the development of K2Ti6O13 materials that have absorption under visible light.

Boron nitrogen (BN) monolayer has attracted considerable attention because of their successful incorporation with graphene based nanodevices. However, many important aspects of the growth mechanisms are still not well explored. Using density functional theory (DFT) calculations, we found that Cu(111) surface is more suitable to be used as a substrate to grow BN monolayer compared with Ni(111) surface. Moreover, we explored that one-dimensional (1D) BN chain configuration is dominant to the two-dimensional (2D) BN ring formation from one pair to five BN pairs deposited on Cu(111) surface. Energetically stable structure transformation of BN monolayer from 1D BN chain to 2D BN ring occurs when the number of pairs is n>5. It is suggested that, as the number of BN pairs increases the energetically stable structures achieve.

High-pressure solid-state metathesis (HPSSM) reaction is an effective route to novel metal nitrides. A recent advance in HPSSM reactions is presented for a number of examples, including 3d transition metal nitrides (ε-Fe3N, ε-Fe3−xCoxN, CrN, and Co4Nx), 4d transition metal nitrides (MoNx), and 5d transition metal nitrides (Re3N, WNx). Thermodynamic investigations based on density functional theory (DFT) calculations on several typical HPSSM reactions between metal oxides and boron nitride indicate that the pressure could reduce the reaction enthalpy ΔH. High-pressure confining environment thermodynamically favors an ion-exchange process between metal atom and boron atom, and successfully results in the formation of well-crystalized metal nitrides with potential applications. Keywords: High-pressure, Solid-state metathesis reaction, Metal nitrides, PACS codes: 62.50.-p, 82.75.Fq

We perform density functional theory calculations to investigate the polaron pair (charge transfer state) photo-generation in donor-acceptor oligomer methyl-capped (4, 7-benzo[2, 1, 3]thiadiazole-2, 6-(4, 4-bis (2-ethylhexyl)-4H-cyclopenta[1, 2-b; 3, 4-b']dithiophene-4, 7-benzo[2, 1, 3]thiadiazole)(CPDTBT).Results show that effective photo-generation of charge transfer state can happen in CPDTBT dimer when the group 4, 7-benzo[2, 1, 3]thiadiazole (BT) in one monomer deviates against the conjugated plane (onset torsion angle is about 20°).The lower excitation energy (530 nm) can only generate the intramolecular excitonic state, while the higher excitation energy (370 nm) can generate the intermolecular charge transfer state, in good agreement with the experiment.Moreover, the mechanism of charge separation in CPDTBT oligomers is discussed.

Spin-crossover (SCO) magnets can act as one of the most possible building blocks in molecular spintronics due to their magnetic bistability between the high-spin (HS) and low-spin (LS) states. Here, the electronic structures and transport properties through SCO magnet Fe(II)-N4S2 complexes sandwiched between gold electrodes are explored by performing extensive density functional theory calculations combined with non-equilibrium Green's function formalism. The optimized Fe-N and Fe-S distances and predicted magnetic moment of the SCO magnet Fe(II)-N4S2 complexes agree well with the experimental results. The reversed spin transition between the HS and LS states can be realized by visible light irradiation according to the estimated SCO energy barriers. Based on the obtained transport results, we observe nearly perfect spin-filtering effect in this SCO magnet Fe(II)-N4S2 junction with the HS state, and the corresponding current under small bias voltage is mainly contributed by the spin-down electrons, which ...

The authors acknowledge financial support from Science and Engineering Research Board (SERB), India (File No. EMR/2017/ 002107). S.B., A.G., and J.D.H. acknowledge Science Foundation Ireland (Grant No. 14/IA/2513). Divya Srivastava would like to acknowledge CSC—the Finnish IT Center for Science for computational resources. Germanium (Ge) plays a crucial role in setting up important functionalities for silicon-compatible photonics. Diamond cubic germanium is an extensively studied semiconductor, although its other exotic forms, like BC8, ST8, ST12 phases, may possess distinct electronic properties. We have fabricated stable ST12-Ge nanowires via a self-seeded bottom-up three phase growth in a confined supercritical toluene environment. Here, we report on the direct evidence of the presence of the ST12 phase by a combination of Raman spectroscopy and first-principles calculations using density functional theory (DFT). It is important to remark that the DFT calculation predicts all the Raman active optical phonon modes of the P 4321 structure, and it is in very good agreement with the experimental results. The phonon dynamics as a function of temperature is investigated through Raman measurements at temperatures varying from 80 to 300 K. First-order temperature coefficients for all the observed Raman modes are estimated from the linear temperature dependence of the phonon shifts. A complete set of isobaric Grüneisen parameters is reported for all Raman modes of ST12-Ge nanowire, and the values are lower compared to the same for Si, dc-Ge bulk, and Ge nanowire. These results have important implications for understanding thermal properties of ST12-Ge nanowire.

Yb14MnSb11 and Yb14MgSb11 have rapidly risen to prominence as high-performing p-type thermoelectric materials for potential deep space power generation. However, the fairly complex crystal structure of 14-1-11 Zintl compounds renders the interpretation of the electronic band structure obscure, making it difficult to chemically guide band engineering and optimization efforts. In this work, we delineate the valence balanced Zintl chemistry of A14MX11 compounds (A = Yb, Ca; M = Mg, Mn, Al, Zn, Cd; X = Sb, Bi) using molecular orbital theory analysis. By analyzing the electronic band structures of Yb14MgSb11 and Yb14AlSb11 , we show that the conduction band minimum is composed of either an antibonding molecular orbital originating from the (Sb3)7− trimer, or a mix of atomic orbitals of A, M, and X. The singly degenerate valence band is comprised of non-bonding Sb p-z orbitals primarily from the Sb atoms in the (MSb4)m- tetrahedra and the of isolated Sb atoms distributed throughout the unit cell. Such a chemical understanding of the electronic structure enables strategies to engineer electronic properties (e.g., the band gap) of A14MX11 compounds.

The microstructure of aqueous CuCl2 has been studied through lots of technologies for many years; however, it remains a controversial subject. In this study, a new spectroscopic method has been proposed to analyze the UV-visible spectra of thin film of CuCl2/H2O solutions at different concentrations. This method is the combination of ratio spectra, difference spectra and second order difference spectra. By using this method, two new bands at ~230 and ~380 nm are obviously observed. The bands are assigned as the contacted ion pairs[CuCl3(H2O)n]- or[CuCl4(H2O)n]2-, which demonstrates that ion pairs exist in the CuCl2/H2O solution. Such finding agrees with the recent theoretical spectra obtained by time-dependent density functional theory. Furthermore, the populations of the contacted ion pairs are discussed. This study not only offers the direct spectroscopic evidence of[CuCl3(H2O)n]- or[CuCl4(H2O)n]2- in aqueous CuCl2, but also suggests that the spectroscopic analysis method is powerful to extract the weak bands in a strong overlapping spectrum.

We investigated the structural evolution and electronic properties of ConC3-/0 and ConC4-/0 (n=1-4) clusters by using mass-selected photoelectron spectroscopy and density functional theory calculations. The adiabatic and vertical detachment energies of Co1-4C3- and Co1-4C4- were obtained from their photoelectron spectra. By comparing the theoretical results with the experimental data, the global minimum structures were determined. The results indicate that the carbon atoms of ConC3-/0 and ConC4-/0 (n=1-4) are separated from each other gradually with increasing number of cobalt atoms but a C2 unit still remains at n=4. It is interesting that the Co2C3- and Co2C4- anions have planar structures whereas the neutral Co2C3 and Co2C4 have linear structures with the Co atoms at two ends. The Co3C3- anion has a planar structure with a Co2C2 four-membered ring and a Co3C four-membered ring sharing a Co-Co bond, while the neutral Co3C3 is a three-dimensional structure with a C2 unit and a C atom connecting to two faces of the Co3 triangle.

The interactions between AgnO− (n=1−8) and H2 (or D2) were explored by combination of the mass spectroscopy experiments and density function theory (DFT) calculations. The experiments found that all oxygen atoms in AgnO− (n=1−8) are inert in the interactions with H2 or D2 at the low temperature of 150 K, which is in contrast to their high reactivity with CO under the same condition. These observations are parallel with the preferential oxidation (PROX) of CO in excess hydrogen catalyzed by dispersed silver species in the condensed phase. Possible reaction paths between AgnO− (n=1−8) and H2 were explored using DFT calculations. The results indicated that adsorption of H2 on any site of AgnO− (n=1−8) is extremely weak, and oxidation of H2 by any kind of oxygen in AgnO− (n=1−8) has an apparent barrier strongly dependent on the adsorption style of the “O”. These experiments and theoretical results about cluster reactions provided molecule-level insights into the activity of atomic oxygen on real silver catalysts.

Fe based oxides are considered as a promising catalyst for the oxygen evolution reaction (OER) due to their low cost and high stability. Here, based on density functional theory calculations, the electrocatalytic behaviors of pure and metal (Ni, Co) doped Fe-terminated Fe2O3(0001) are investigated. The potential-limiting step for OER is determined as the formation of O* by dehydrogenating surface hydroxyl and it is suggested that the doping enhances the catalytic activity of Fe2O3(0001) by reducing the free energy change of rate limiting step on doped Ni or Co atom. Especially, the calculated over-potential of Co-doped Fe2O3 (0001) surface is about 0.63 eV on Co site, which is comparable with the theoretical over-potential of 0.56 eV for RuO2.

We perform first-principles simulations on a type of two-dimensional metal-organic nanosheet derived from the recently reported manganese bis-dithiolene Mn3C12S12 [Nanoscale 5, 10404 (2013)] and manganese bis-diamine Mn3C12N12H12 [ChemPhysChem 16, 614 (2015)] monolayers. By coordinating chalcogen (S or O) atoms and -NH- group to Mn atoms with trans- or cis-structures and preserving space inversion symmetry, four configurations of this type of nanosheet are obtained: trans-manganese dithiolene-diamine Mn3(C6S3N3H3)2, cis-manganese dithiolene-diamine Mn3(C6S6)(C6N6H6), trans-manganese dihydroxyl-diamine Mn3(C6O3N3H3)2, and cis-manganese dihydroxyl-diamine Mn3(C6O6)(C6N6H6). The geometric configuration, electronic structure and magnetic properties of these metal-organic nanosheets are systematically explored by density functional theory calculations. The calculated results show that Mn3(C6S3N3H3)2, Mn3(C6O3N3H3)2 and Mn3(C6O6)(C6N6H6) monolayers exhibit half-metallicity and display strong ferromagnetism with Curie transition temperatures near and even beyond room temperature, and Mn3(C6S6)(C6N6H6) monolayer is a semiconductor with small energy gap and spin frustration ground state. The mechanisms for the above properties, especially influences of different groups (atoms) substitution and coordination style on the magnetism of the nanosheet, are also discussed. The predicted two-dimensional metal-organic nanosheets have great promise for the future spintronics applications.

Graphene nanomaterials functionalized with oxygen groups [graphene oxide (GO) and reduced GO (rGO)] are either doped with element nitrogen or nitrogen-containing aromatic moieties followed by the investigation of electrochemical properties that generally show enhanced electroanalytical performance. We studied structural, morphological, and physical–chemical properties using correlative techniques. While we attribute their improved properties promoted simultaneously by topologically interconnected mesoporous network morphology, the presence of heteroatom species, and lattice vibrational structure, the complex interpretation requires the need to supplement the experimental observations with theoretical calculations for further insights. The complex interplay of pore size and redox properties revealing distinctive supercapacitive (ion-adsorption controlled) and pseudocapacitive (diffusion-controlled) energy storage mechanistic contributions arises from the combined effects of oxygen and nitrogen functional groups, most likely located on the basal plane and at the pore edge plane sites. The density functional theory calculations provided band structure and electron transfer from Mulliken and Hirshfeld population analyses helping discern the nature of various functional groups in diverse graphene. Interestingly, while quaternary (N—Q) and pyridinic-N-oxides (N—O) on the basal planes show enhanced capacitance due to positive charge and thus an improved electron transfer at higher current loads identified in nitrogen-doped aerogel (AG/nitrogenated) and GO-derived rGO by chemical and electrochemical properties, the other important functional groups affecting the energy storage are pyridinic (N-6) and pyrrolic (N-5) nitrogen groups on the edge of the rGO nanosheet in association with carboxylic (—COOH) and quinone (C=O) functional groups in nitrogenated functional graphene/graphene aerogel and rGO coated polyaniline, contributing to a pseudocapacitive character.

A power figure-of-merit (FOM) of ∼62.6–87.3 GW/cm2 is predicted for ScAlN, which represents a value 5–7 times larger than that of GaN. The parameters for the lattice-matched Sc0.18Al0.82N FOM calculation are investigated by first-principles density functional theory (DFT) calculations with the local density approximation. An energy gap of 5.65 eV and an electron effective mass of 0.46m0 are obtained from the DFT band structure calculation of Sc0.1875Al0.8125N. The electron mobility of Sc0.18Al0.82N is simulated based on Boltzmann transport equations, which consider scatterings by ionized impurities, dislocations, alloy scattering, acoustic phonons, and optical phonons. The remarkable power FOM shows that lattice-matched Sc0.18Al0.82N possesses a large breakdown voltage and low specific on-resistance, which suggests the great potential for Sc0.18Al0.82N to be implemented in high-voltage power electronics for improved device performance.

International audience; In this Letter, we report on the role of Se incorporation in the increased efficiency recently measured in Se alloyed cadmium telluride (CdTe) absorbers. This is done by means of density functional theory calculations following an extensive exploration of all the possible diffusion paths of Se. We identify a unique two-step mechanism that accounts for bulk diffusion of chalcogenide interstitials in CdTe, explaining the Se diffusion measured in experiments. The interaction of the diffusing interstitial with the Cd vacancy and the Te antisite is further analyzed in order to understand the passivation of these two main non-radiative recombination centers. Taking into account the approach path of Se, we identify nine complexes that present different levels of passivation. The lowest formation energy is achieved for a ⟨100⟩ Te dimer with two Se in the first neighbor shell. This defect also presents the shallowest donor character defect state due to the presence of Se. This highlights the hybrid role of Se in the mechanism of increased efficiency: it first mediates the diffusion of chalcogenide toward the non-radiative recombination centers before it leads with Te to their optimal passivation. This comprehensive insight should allow further improvements in CdTe-based technologies.

Strontium titanate (SrTiO3 ) has received much attention due to its wide range of potential applications, including in electrochemical devices such as solid oxide fuel cells and capacitors. The stability and safety features of SrTiO3 led to the development of promising electrodes for Li-ion batteries. Here, we use density functional theory simulations to examine the incorporation of lithium from its gas-phase and bulk forms. The results show that a single Li atom is thermodynamically stable in bulk SrTiO3 with respect to its gas-phase and slightly unfavorable compared to its bulk. Multiple Li incorporation up to six is also considered, and the incorporation is exoergic with respect to both gas-phase and bulk forms. Charge analysis confirmed the presence of Li+ ions in the lattice. Li incorporation turns the insulating nature of SrTiO3 into metallic and non-magnetic into magnetic. Lithium incorporation facilitates the formation of Sr, Ti, and O vacancies. The loss of Li2 O is exoergic, suggesting that oxygen vacancy mediated self-diffusion will be promoted.

First-principles calculations based on density functional theory were employed to study the adsorption of gas molecules (CH4, CO, H2O) on various SnO2 (110) surfaces. We found that CO and CH4 molecules are weakly adsorbed on intrinsic SnO2 (110) surfaces, and intrinsic SnO2 is sensitive only to the H2O molecule. Compared with the gas molecules adsorbed on the intrinsic SnO2 surfaces, the significantly increased adsorption energy indicates that there is an improvement in the gas sensitivity properties of Co-doped SnO2 (Co/SnO2) and oxygen vacancy modified Co-doped SnO2 (Co/VO/SnO2) to CO, CH4, and H2O gas. The CO adsorbed on the Co/VO/SnO2 surface has the strongest adsorption energy (−1.402 eV). We also studied the optical properties of the Co/SnO2 and Co/VO/SnO2 surfaces influenced by the three gas molecules. We found that the three gas molecules cause an enhancement of the adsorption peaks of Co/SnO2 configuration in the visible light range. Our study benefits research on the potential application of SnO2 sensor materials.

Vanadium dioxide is an unusual material that undergoes a first-order Metal–Insulator Transition (MIT) at 340 K, attracting considerable interest for its intrinsic properties and its potential applications. However, the nature of MIT has not been fully determined. Variants of density functional theory (DFT) have been widely used to study the MIT in pure and doped VO2. A full description of MIT is complicated by several related factors such as V–V dimerization, magnetic properties, and spin correlations. Each of these requires careful attention. In this Perspective, we explain why DFT fails, introduce a spin-pairing model of MIT, and propose a new way to estimate the transition temperature. We then use the method to study the doping and alloying process. Finally, we give an overview of some applications of MIT. This work aims to provide insight into and stimulate more research studies in this promising field.

We develop the relationship between the strain derivative of the mean-inner potential and surface contributions to flexoelectricity, identifying the true surface-specific component of the flexoelectric response of finite samples. Density functional theory calculations on a range of experimentally observed, low energy SrTiO3, MgO, and Si surfaces demonstrate that the mean-inner potential and its contributions to flexoelectricity are sensitive to small differences in surface structure, chemistry, and adsorbates. We also introduce a method to estimate mean-inner potential contributions to flexoelectricity using electron scattering factors and use this approximation to predict total flexoelectric responses for a variety of insulators. Strategies to experimentally disentangle bulk and surface flexoelectric terms are also discussed.

The structural and optoelectronic properties of a novel ZnI2/CdS van der Waals (vdW) heterostructure are studied under the effect of biaxial strain based on the density functional theory. Our results show that the ZnI2/CdS vdW heterostructure is dynamically and thermally stable depending on the molecular dynamics simulation and phonon dispersion curve. The results also indicate that the ZnI2/CdS heterostructure exhibits type-II band alignment with an indirect energy gap of 0.886 and 1.336 eV according to the Perdew–Burke–Ernzerhof and Heyd–Scuseria–Ernzerhof methods, respectively. Besides, the biaxial strain has a significant impact on the electronic properties. The energy bandgap of the ZnI2/CdS heterostructure decreases gradually as the compressive strain increases, reaching a minimum value of 1.162 eV at −6%. Also, a transformation from indirect bandgap to direct bandgap appears at strains of 4% and 6%. Broadly, it has been found that the optical properties of the ZnI2/CdS vdW heterostructure improve under the influence of strain, and the absorption coefficient can reach 105 cm−1 with the emergence of a shift phenomenon that expands the absorption capacity. Therefore, the application of strain will drastically improve the optical and electronic properties of the ZnI2/CdS vdW heterostructure, providing a roadmap for enhancing optical efficiency in photocatalytic and photovoltaic devices.

The optical and electronic properties of the {\alpha}-SiTe, {\beta}-SiTe, and RX-SiTe_2 are investigated. A detailed analysis of electronic properties is done using standard density functional theory (DFT) and hybrid functional (HSE06) methods. The optical dielectric properties are studied under three different methods: standard DFT, many-body Green's functions (GW), and Bethe-Salpeter equation (BSE). Our calculations show that the SiTe compounds possess extremely high static dielectric constants in their bulk forms ({\epsilon}_0({\bot}) = 68.58, {\epsilon}_0({\parallel}) = 127.29 for {\alpha}-SiTe, and {\epsilon}_0({\bot}) = 76.23, {\epsilon}_0({\parallel}) = 98.15 for {\beta}-SiTe). The frequency-dependent dielectric functions Im({\epsilon}) have very large values (>100) in the optical regime, which are among the highest of layered materials, suggesting them as excellent light absorbents in the corresponding frequencies. {\alpha}-SiTe exhibits a high degree of optical anisotropy as compared to the other two compounds, consistent with their structural configurations. A strong interlayer excitonic effect is observed in bulk RX-SiTe_2. In addition, an analysis of Raman intensity is also performed.

Room temperature light emission from optically active defect centers in two-dimensional layered materials has attracted great interest in recent years owing to the critical applications in the field of quantum information technologies. Therefore, efficient generation, detection, characterization, and manipulation of spatially localized emission from the defect centers are of crucial importance. Here, we report localized, stable, and bright room temperature photoluminescence (PL) emission from defects in WO3. In particular, the experimentally observed polarized and power dependent PL emission shows single photon characteristics. In addition, density functional theory calculations indicate that the source of the emission is most probably oxygen vacancy defects in WO3. The PL emission obtained from the localized defect centers in WO3 at room temperature has been, further, enhanced more than 20 times by using plasmonic gold nanoparticles.

Carbon materials and their unique properties have been extensively studied by molecular dynamics, thanks to the wide range of available carbon bond order potentials (CBOPs). Recently, with the increase in popularity of machine learning (ML), potentials such as Gaussian approximation potential (GAP), trained using ML, can accurately predict results for carbon. However, selecting the right potential is crucial as each performs differently for different carbon allotropes, and these differences can lead to inaccurate results. This work compares the widely used CBOPs and the GAP-20 ML potential with density functional theory results, including lattice constants, cohesive energies, defect formation energies, van der Waals interactions, thermal stabilities, and mechanical properties for different carbon allotropes. We find that GAP-20 can more accurately predict the structure, defect properties, and formation energies for a variety of crystalline phase carbon compared to CBOPs. Importantly, GAP-20 can simulate the thermal stability of C60 and the fracture of carbon nanotubes and graphene accurately, where CBOPs struggle. However, similar to CBOPs, GAP-20 is unable to accurately account for van der Waals interactions. Despite this, we find that GAP-20 outperforms all CBOPs assessed here and is at present the most suitable potential for studying thermal and mechanical properties for pristine and defective carbon.

Two-dimensional transition metal carbides, carbonitrides, and nitrides, called MXenes, exhibit high metallic conductivity, ion intercalation capability, and reversible redox activity, prompting their applications in energy storage and conversion, electromagnetic interference (EMI) shielding, and electronics, among many other fields. It has been shown that replacement of ∼50% of carbon atoms in the most popular MXene family member, titanium carbide (Ti3C2Tx), by nitrogen atoms, forming titanium carbonitride (Ti3CNTx), leads to drastically different properties. Such properties include very high negative charge in solution and extreme EMI shielding effectiveness, exceeding all known materials, even metals at comparable thicknesses. Here, by using ultraviolet photoemission spectroscopy (UPS), the electronic structures of Ti3CNTx and Ti3C2Tx are systematically investigated and compared as a function of charge carrier density. We observe that, in contrast to Ti3C2Tx, the Ti 3p core-level of Ti3CNTx exhibits a counterintuitive shift to a lower binding energy of up to ∼250 meV upon increasing the electron density, which is a spectroscopic signature of negative electronic compressibility (NEC). These experimentally measured chemical potential shifts are well captured by the density functional theory (DFT) calculation. The DFT results also further suggest that the hybridization of titanium–nitrogen bonding in Ti3CNTx helps to promote the available states of Ti atoms for receiving more electrons above the fermi level and leads to the observed NEC. Our findings explain the differences in electronic properties between the two very important and widely studied MXenes and also suggest a new strategy to apply the NEC effect of Ti3CNTx in energy and charge storage applications.

This Letter reports an original spin valve device that is based on a chiral templated nickel material. Chirality in Ni is induced by exploiting co-electrodeposition of an organic chiral template. In this specific case, the chiral templating is enantiopure tartaric acid (TA). Facile electrodeposition (co-deposition) in ambient conditions produces a nickel chiral-templated material. Z-shaped magnetoresistance curves, switching sign as a function of TA handedness, prove the peculiar ferromagnetic character induced by the presence of a chiral compound. Synchrotron measurements using circular polarized light, x-ray natural circular dichroism, confirm the chirality of the Ni in the TA/Ni composite. Density functional theory calculation proves the existence of a strong electronic delocalization involving the tartaric acid and Ni. The significant finding of this Letter is that chiral templated Ni paves the way for future spin valve, which will be able to control the spin without an external magnetic field (as indeed foreseen within the chiral induced spin selectivity-effect framework).

Ionic compounds exhibit great structural diversity that can be used for tailoring novel nanostructured materials with distinct technological applications. In particular, significant progress has been made in the development of inorganic nanotubes, where the introduction of polar chemical bonds dramatically affects their physical properties in comparison to their carbon-based analogs. In this work, we apply density functional theory methods combined with plane-wave basis sets and periodic boundary conditions to investigate structural and electronic properties of prototypical lithium fluoride nanotubes featuring armchair, zig-zag, and square sheet (SSNT) configurations. Our results indicate that the zig-zag nanotubes can be formed from the more stable SSNT structures by the application of a positive axial strain, where an upper value of 1.44 eV for the activation energy is obtained. Furthermore, the zig-zag structures become more stable with the increasing nanotube radius, being merely 0.13 eV higher in energy than SSNT for the (10,0) case. All nanotubes investigated herein are insulators, with bandgap energies in the range of 8.33–8.59 eV for armchair and 7.91–8.54 eV for SSNT configurations. The latter nanotubes have higher Young’s modulus, and consequently greater stiffness, than the corresponding armchair analogs. The small strain energies computed for the SSNT and armchair nanotubes reveal their high stability, making them promising candidates for experimental realization.

The MTX-based compounds are promising rare-earth-free candidates for multicaloric applications due to the proximity of their structural and magnetic phase transitions. In this paper, we use first principles calculations to study how chemical pressure affects the energetics, saturation magnetization, and volume change. Our calculations reveal the presence of a complex interplay between the M-, T-, and X-site elements in tuning the properties. The choice of elements for rational alloy design should be informed by the site-specific response. Our work motivates future synthesis and characterization efforts to focus on uncovering site-specific data to tailor strategies for maximizing the caloric response and bridge the knowledge-gap.

Proper coupling between structural and magnetic transitions is critical for the emergence and control of magnetocaloric effects in solids. We examine the influence of minor substitutional doping (replacing Mn by Cr and Al by Sn) and interstitial doping with B on the magnetic, structural, and magnetocaloric properties of recently discovered Mn0.5Fe0.5NiSi0.94Al0.06 alloy exhibiting a giant magnetocaloric effect near room temperature. We demonstrate that magnetocaloric properties of the base compound can be controlled and, in some cases, improved by chemical substitutions. First-principles computations elucidate how small changes in the composition affect properties in this family of compounds and, thus, provide useful guidance for the selection of suitable doping elements for such materials. The magnetic-field-induced entropy change measured for Mn0.5Fe0.5NiSi0.94Al0.06B0.005 is −22 J/kg K near room temperature for the applied magnetic field of 2 T, and it is among the highest known values for this class of materials.

Properties of AlN/GaN surfaces are important for realizing the tunability of devices, as the presence of surface states contributes to Fermi level pinning. This pinning can influence the performance of high electron mobility transistors and is also important for passivation of the surface when developing high-power electronic devices. It is widely understood that both AlN and GaN surfaces oxidize. Since there are many possible reconstructions for each surface, it is a challenge to identify the relevant surface reconstructions in advance of a detailed simulation. Because of this, different approaches are often employed to down select initial structures to reduce the computational load. These approaches usually rely on either electron counting rules or oxide stoichiometry, as both of these models tend to lead to structures that are energetically favorable. Here we explore models from these approaches but also explore a reconstruction of the (0001) surface directly observed using scanning transmission electron microscopy with predictive density functional theory simulations. Two compositions of the observed surface reconstruction—one which obeys oxide stoichiometry and one which is cation deficient and obeys electron counting—are compared to reconstructions from the previous work. Furthermore, surface states are directly calculated using hybrid exchange-correlation functionals that correct for the underestimation of the bandgaps in AlN and GaN and improve the predicted positions of surface states within the gap. It is found that cation deficiency in the observed reconstruction yields surface states consistent with the experiment. Based on all of these results, we provide insight into the observed properties of oxidized AlGaN surfaces.

Erythritol has been proposed as an inert surrogate for developing theoretical and computational models to study aging in energetic materials. In this work, we present a comparison of mechanical and shock properties of erythritol computed using the ReaxFF reactive force field and from ab initio calculations employing density functional theory (DFT). We screened eight different ReaxFF parameterizations, of which the CHO parameters developed for hydrocarbon oxidation provide the most accurate predictions of mechanical properties and the crystal structure of erythritol. Further validation of the applicability of this ReaxFF parameterization for modeling erythritol is demonstrated by comparing predictions of the elastic constants, crystal structure, vibrational density of states, and Hugoniot curves against DFT calculations. The ReaxFF predictions are in close agreement with the DFT simulations for the elastic constants and shock Hugoniot when the crystal is loaded along its c axis but show as much as 30% disagreement in the elastic constants in the a b plane and 12% difference in shock pressures when shocked along the a or b crystal axes. Last, we compare thermomechanical properties predicted from classical molecular dynamics with those calculated using the quasi-harmonic approximation and show that quantum mechanical effects produce large discrepancies in the computed values of heat capacity and thermal expansion coefficients compared with classical assumptions. Combining classical molecular dynamics predictions of mechanical behavior with phonon-based calculations of thermal behaviors, we show that predicted shock-induced temperatures for pressures up to 6.5 GPa do not exceed the pressure-dependent melting point of erythritol.

First-principles calculations within the density functional theory (DFT) are addressed to study the energetic stability and the electronic, magnetic, and optical properties of embedded nanodomains (NDs) formed by threefold coordinated Si and C atoms within a hydrogenated silicon carbide (H-SiC) monolayer. The total energy calculations show that these nanodomains have low formation energy and act as two-dimensional quantum dots (2D QDs), giving rise to localized electronic levels inside the H-SiC bandgap. The stability of the QDs is ruled by their size and shape. For NDs where the number of threefold Si and C atoms are the same, the system is a nonmagnetic semiconductor, whereas if the number of threefold coordinated Si and C atoms is different, the system is a magnetic semiconductor with a magnetic moment of 1 μ B per unpaired (Si or C) atom present in the QDs. The calculated optical spectra show that there is a strong absorption optical in the visible region, and the position of the optical absorption peaks presents a dependence with the size and shape of the QDs. These findings are in accordance with previous works where 2D SiC QDs were investigated and the results suggest that 2D SiC QDs are potential materials for optical applications. Furthermore, our DFT results can be used to obtain 2D SiC QDs with desirable electronic, magnetic, and optical properties to be employed in nanodevices.

The edge elasticity and its effect on flexoelectric response of the Janus MoSSe nanoribbons are systematically explored by means of density functional theory based first-principles calculations. We report edge stresses, edge elastic moduli, and structural deformations of the Janus MoSSe nanoribbons with various widths. It is shown that both armchair and zigzag terminated edges of the MoSSe nanoribbons are essentially subjected to tension, due to the existence of the edge stresses. The magnitude of average zigzag edge stresses is much larger than that of the average armchair ones. Furthermore, our results show that both misfit strain induced by asymmetric chalcogen atomic layers, and the edge stresses cause the spontaneous bending deformation of such Janus nanoribbons. More importantly, flexoelectronic properties of semiconducting armchair MoSSe nanoribbons are carefully evaluated and compared with those of armchair MoS 2 and MoSTe nanoribbons. In particular, it is found that the out-of-plane flexoelectronic coefficients strongly depend on their widths. Additionally, the flexoelectric response resulting from spontaneous bending is weaker than that from the opposite one. The implicit mechanisms on deformations and flexoelectronic properties of such Janus nanoribbons have been carefully explored. The results in this work provide useful insights into their potential applications in nanoscale electromechanical systems.

Exciton binding energy is an important factor in photovoltaics as the formation of excitons influences the charge separation in solar cells. However, a detailed theoretical study of excitonic properties is rather demanding due to huge computational cost. We have systematically applied several state-of-the-art advanced first-principles based methodologies, viz., hybrid density functional theory combined with Spin–Orbit Coupling (SOC), Many Body Perturabtion Theory (MBPT), model-BSE, Wannier–Mott, and Density Functional Perturbation Theory (DFPT) approaches, to understand the excitonic properties by taking a prototypical model system of lead bromide perovskites, viz., APbBr3 [A = CH 3 NH 3 + (MA), HC ( NH 2 ) 2 + (FA), Cs+]. We show that via conventional procedure using GW/BSE approach along with SOC effect, it is very challenging to converge the BSE calculation to obtain the correct position of the excitonic peak to compute the exciton binding energy (EB) accurately. Therefore, we have employed Wannier–Mott and DFPT approaches to compute EB, where we find that the contribution of ionic dielectric screening is essential. In addition, we have calculated the exciton lifetime, which is in agreement with the trend observed (FAPbBr3 > MAPbBr3 > CsPbBr3) for electron–phonon coupling. The role of cation “A” for achieving the long-lived exciton lifetime is also explained and well understood.

Magnetic properties of Fe100−xGax (x = 15 and 30) epitaxial thin films on GaAs(001) substrates were studied experimentally and theoretically. The samples grown by molecular beam epitaxy under certain conditions adopt body-centered structures with tetragonal distortion along the film normal with a c/a ratio varying from 1.014 to 1.036. The density functional theory (DFT) calculations were performed for different (c/a) ratio values and Ga contents. DFT results showed that Fe atoms placed at the first neighborhood of Ga positions present a much stronger distortion in the local exchange-correlation field than second neighbor Fe atoms. The formation of non-bonding Fe 3d states in the minority spin sub-band and the predominance of hybridization of Ga 4p states with Fe 4p states due to Ga content cause this magnetic behavior. The in-plane magnetic anisotropies are explained in terms of the exchange-correlation field isosurfaces. As a result of that, the global magnetic anisotropy can be described as cubic magnetocrystalline mixed with sixfold anisotropy.