Including Spin Orbit Research Articles

Relativistic Douglas–Kroll–Hess calculations of hyperfine interactions within first-principles multireference methods

A relativistic magnetic hyperfine interaction Hamiltonian based on the Douglas–Kroll–Hess (DKH) theory up to the second order is implemented within the ab initio multireference methods, including spin–orbit coupling in the Molcas/OpenMolcas package. This implementation is applied to calculate relativistic hyperfine coupling (HFC) parameters for atomic systems and diatomic radicals with valence s or d orbitals by systematically varying active space size in the restricted active space self-consistent field formalism with restricted active space state interaction for spin–orbit coupling. The DKH relativistic treatment of the hyperfine interaction reduces the Fermi contact contribution to the HFC due to the presence of kinetic factors that regularize the singularity of the Dirac delta function in the nonrelativistic Fermi contact operator. This effect is more prominent for heavier nuclei. As the active space size increases, the relativistic correction of the Fermi contact contribution converges well to the experimental data for light and moderately heavy nuclei. The relativistic correction, however, does not significantly affect the spin-dipole contribution to the hyperfine interaction. In addition to the atomic and molecular systems, the implementation is applied to calculate the relativistic HFC parameters for large trivalent and divalent Tb-based single-molecule magnets (SMMs), such as Tb(III)Pc2 and Tb(II)(CpiPr5)2 without ligand truncation using well-converged basis sets. In particular, for the divalent SMM, which has an unpaired valence 6s/5d hybrid orbital, the relativistic treatment of HFC is crucial for a proper description of the Fermi contact contribution. Even with the relativistic hyperfine Hamiltonian, the divalent SMM is shown to exhibit strong tunability of HFC via an external electric field (i.e., strong hyperfine Stark effect).

Two-dimensional altermagnets from high throughput computational screening: Symmetry requirements, chiral magnons, and spin-orbit effects

We present a high throughput computational search for altermagnetism in two-dimensional (2D) materials based on the Computational 2D Materials Database (C2DB). We start by showing that the symmetry requirements for altermagnetism in 2D are somewhat more strict compared to bulk materials and applying these yields a total of seven altermagnets in the C2DB. The collinear ground state in these monolayers is verified by spin spiral calculations using the generalized Bloch theorem. We focus on four d-wave altermagnetic materials belonging to the P21′/c′ magnetic space group—RuF4, VF4, AgF2, and OsF4. The first three of these are known experimentally as van der Waals bonded bulk materials and are likely to be exfoliable from their bulk parent compounds. We perform a detailed analysis of the electronic structure and non-relativistic spin splitting in k-space exemplified by RuF4. The magnon spectrum of RuF4 is calculated from the magnetic force theorem, and it is shown that the symmetries that enforce degenerate magnon bands in anti-ferromagnets are absent in altermagnets and give rise to the non-degenerate magnon spectrum. We then include spin–orbit effects and show that these will dominate the splitting of magnons in RuF4. Finally, we provide an example of i-wave altermagnetism in the 2H-phase of FeBr3.

Quantum-mechanical study of a MO2(cyclam)+ complexes series with M = Mn, Tc, Re

This work focuses on the theoretical study of nd2 pentavalent group 7 metal ions (Mn, Tc, Re) electronic structures complexed with cyclam (MO2(cyclam)+) via DFT due to their fascinating photochemical and electrochemical properties. Optical properties were studied via TD-DFT modeling ground (S0) and first excited (S1 and T1) states including spin–orbit effect induced in the absorption and emission spectra. Metal-ligand interactions were studied via EDA-NOCV analysis. DFT suggests increase stability as the metal gets bigger. MLCT and LMCT mechanisms can modulate the optical properties of cyclam ligand and could confer photocatalytic properties under visible light. Deactivation mechanisms shows dark states in all studied complexes. EDA-NOCV results show metal/cyclam interaction with covalent character for all systems, while the metal/oxygens interaction presents large electrostatic character where charge flow happens from cyclam ligand toward nd2-metal orbitals. All theoretical results suggest that MnO2(cyclam)+(a) will display similar properties to reported compounds TcO2(cyclam)+(b) and (ReO2(cyclam)+(c).

Size effects on polaron formation in lead chloride perovskite thin films

Lead halide perovskites (LHP) are of interest for light-emitting applications due to the tunability of their bandgap across the visible and near-infrared spectrum (IR) coupled with efficient photoluminescence quantum yields (PLQY). It is widely speculated that photoexcited electrons and holes spatially separate into large negative (electron) and positive (hole) polarons. Polarons are expected to be optically active. With the observed optoelectronic signatures expecting to show potential excited states within the polaronic potential well. From the polaron excited-state we predict that large polarons should be capable of spontaneous emission, photoluminescence, in the mid-IR to far-IR regime based on the concept of inverse occupations within the polaron potential well. Here we use density functional theory (DFT), including spin–orbit coupling interactions, for calculations on a two-dimensional Dion-Jacobson (DJ) lead chloride perovskite atomistic model of various sizes as a host material for either negative or positive polarons to examine the effects of size on polaron formation. This work provides computational evidence that polaron formation through selective charge injection does not show the same level of localisation for positive and negative polarons.

A Comprehensive Study of Electronic, Optical, and Thermoelectric Characteristics of Cs2PbI2Br2 Inorganic Layered Ruddlesden-Popper Mixed Halide Perovskite through Systematic First-Principles Analysis.

In this research, we present a comprehensive study on the influence of layer-dependent structural, electronic, and optical properties in the two-dimensional (2D) Ruddlesden-Popper (RP) perovskite Cs2PbI2Br2. Employing first-principles computations within the density functional theory method, including spin orbit coupling contribution, we examine the impact of various factors on the material. Our results demonstrate that the predicted 2D-layered RP perovskite Cs2PbI2Br2 structures exhibit remarkable stability both structurally and energetically, making them promising candidates for experimental realization. Furthermore, we observe that the electronic band gap and optical absorption coefficients of Cs2PbI2Br2 strongly depend on the thickness variation of the layers. Interestingly, Cs2PbI2Br2 exhibits a notable absorption coefficient in the visible region. Using a combination of density functional theory and Boltzmann transport theory, the thermoelectric properties were forecasted. The calculation involved determining the Seebeck coefficient (S) and other associated thermoelectric characteristics, such as electronic and thermal conductivities, as they vary with the chemical potential at room temperature. These findings open up exciting opportunities for the application of this 2D RP perovskite in solar cells and thermoelectric devices, owing to its unique properties.

Transition probabilities of the AgS(A[formula omitted][formula omitted] X[formula omitted]) emission including spin–orbit coupling effects and evidence of a novel band system

A systematic spectroscopic work using multireference configuration interaction (MRCI) and coupled cluster (CC) calculations was performed in conjunction with large basis sets for AgS. As a result, a more accurate dissociation energy of 17,542 cm−1 is predicted for the X2Π using an analytical potential energy curve, including spin–orbit effects. The calculated energy separation Te(A)∼ 10,500 cm−1 suggests that the AgS(A2Σ+→ X2Π) band system is in near-IR. An unobserved 32Π→ X2Π band system is predicted with Einstein coefficient for spontaneous emission of the orders of 104–105 s−1 in the UV region (342 nm). The radiative lifetimes for the A2Σ+ are of the order of ∼100 microseconds. The AgS(A) state presents a possible predissociation channel caused by interactions with the quartet 14Σ− and 14Π states. The spin–orbit coupling effects are considered in this work by utilizing the Breit–Pauli operator. The present findings are good references for future spectroscopic research concerning heavy-element sulfides.

Anisotropy in colossal piezoelectricity, giant Rashba effect and ultrahigh carrier mobility in Janus structures of quintuple Bi2X3 (X = S, Se) monolayers

Due to the asymmetric structures, two-dimensional Janus materials have gained significant attention in research for their intriguing piezoelectric and spintronic properties. In the present work, quintuple Bi2X3 (X = S, Se) monolayers (MLs) have been modified to create stable Janus Bi2X2Y (X ≠ Y = S, Se) MLs that display piezoelectricity in both the planes along with Rashba effect. The out-of-plane piezoelectric constant (d 33) is 41.18 (−173.14) pm V−1, while the in-plane piezoelectric constant (d 22) is 5.23 (6.21) pm V−1 for Janus Bi2S2Se (Bi2Se2S) ML. Including spin–orbit coupling in the Janus MLs results in anisotropic giant Rashba spin splitting (RSS) at the Γ point in the valence band, with RSS proportional to d 33. The Rashba constant along the Γ–K path, , is 3.30 (2.27) eV Å, whereas along Γ–M, is 3.58 (3.60) eV Å for Janus Bi2S2Se (Bi2Se2S) ML. The MLs exhibit ultrahigh electron mobility (∼5442 cm2V−1s−1) and have electron to hole mobility ratio of more than 2 due to their tiny electron-effective masses. The flexibility of the MLs allows for a signification alteration in its properties, like band gap, piezoelectric coefficient, and Rashba constant, via mechanical (biaxial) strain. For the MLs, band gap and d 33 value are enhanced with compressive strain. The d33 value of Janus Bi2Se2S reaches 4886.51 pm V−1 under compressive strain. The coexistence of anisotropic colossal out-of-plane piezoelectricity, giant RSS, and ultrahigh carrier mobilities in Janus Bi2S2Se and Bi2Se2S MLs showcase their tremendous prospects in nanoelectronic, piezotronics, and spintronics devices.

Type II multiferroic order in two-dimensional transition metal halides from first principles spin-spiral calculations

We present a computational search for spin spiral ground states in two-dimensional transition metal halides that are experimentally known as van der Waals bonded bulk materials. Such spin spirals break the rotational symmetry of the lattice and lead to polar ground states where the axis of polarization is strongly coupled to the magnetic order (type II multiferroics). We apply the generalized Bloch theorem in conjunction with non-collinear density functional theory calculations to find the spiralling vector that minimizes the energy and then include spin–orbit coupling to calculate the preferred orientation of the spin plane with respect to the spiral vector. We find a wide variety of magnetic orders ranging from ferromagnetic, stripy anti-ferromagnetic, 120∘ non-collinear structures and incommensurate spin spirals. The latter two introduce polar axes and are found in the majority of materials considered here. The spontaneous polarization is calculated for the incommensurate spin spirals by performing full supercell relaxation including spinorbit coupling and the induced polarization is shown to be strongly dependent on the orientation of the spiral planes. We also test the effect of Hubbard corrections on the results and find that for most materials LDA + U results agree qualitatively with LDA. An exception is the Mn halides, which are found to exhibit incommensurate spin spiral ground states if Hubbard corrections are included whereas bare LDA yields a 120∘ non-collinear ground state.

High-Temperature Thermodynamics of Uranium from Ab Initio Modeling

We present high-temperature thermodynamic properties for uranium in its γ phase (γ-U) from first-principles, relativistic, and anharmonic theory. The results are compared to CALPHAD modeling. The ab initio electronic structure is obtained from density-functional theory (DFT) that includes spin–orbit coupling and an added self-consistent orbital-polarization (OP) mechanism for more accurate treatment of magnetism. The first-principles method is coupled to a lattice dynamics scheme that is used to model anharmonic lattice vibrations, namely, Self-Consistent Ab Initio Lattice Dynamics (SCAILD). The methodology can be summarized in the acronym DFT + OP + SCAILD. Upon thermal expansion, γ-U develops non-negligible magnetic moments that are included for the first time in thermodynamic theory. The all-electron DFT approach is shown to model γ-U better than the commonly used pseudopotential method. In addition to CALPHAD, DFT + OP + SCAILD thermodynamic properties are compared with other ab initio and semiempirical modeling and experiments. Our first-principles approach produces Gibbs free energy that is essentially identical to CALPHAD. The DFT + OP + SCAILD heat capacity is close to CALPHAD and most experimental data and is predicted to have a significant thermal dependence due to the electronic contribution.

Structural, electronic, and optical properties of orthorhombic and hexagonal phases of Bi2Se3: First-principles study

In this work, we present structural, electronic, and optical properties of Bi2Se3 using first-principles calculations based on density functional theory (DFT) including spin orbit coupling (SOC)). Bi2Se3 is well known V–VIth group chalcogenide material shows excellent thermoelectric properties and suitable for optoelectronic devices. The calculations were performed using computational code SIESTA using generalized gradient approximation (GGA) Perdew–Burke–Eruzerhof for solids (PBESol) functionals. The obtained indirect band gaps of Bi2Se3 were 0.12 eV and 1.14 eV and obtained refractive index along x-direction were 5.48 and 1.96 for hexagonal and orthorhombic phases, respectively. The absorption results showed that the hexagonal Bi2Se3 absorb IR radiations while orthorhombic Bi2Se3 absorbs Nr-IR radiations. Hence both the phases of Bi2Se3 are suitable for detector applications. Bi2Se3 with large indirect band gap in orthorhombic phase is more suitable for band-to-band tunnelling transistors and optoelectronic devices.

Current density functional framework for spin–orbit coupling

Relativistic two-component density functional calculations are carried out in a non-collinear formalism to describe spin-orbit interactions, where the exchange-correlation functional is constructed as a generalization of the non-relativistic density functional approximation. Contrary to non-relativistic density functional theory (DFT), spin-orbit coupling, however, leads to a non-vanishing paramagnetic current density. Density functionals depending on the kinetic energy density, such as meta-generalized gradient approximations, should therefore be constructed in the framework of current DFT (CDFT). The latter has previously exclusively been used in the regime of strong magnetic fields. Herein, we present a consistent CDFT approach for relativistic DFT, including spin-orbit coupling. Furthermore, we assess the importance of the current density terms for ground-state energies, excitation energies, nuclear magnetic resonance shielding, and spin-spin coupling constants, as well as hyperfine coupling constants, Δg-shifts, and the nuclear quadrupole interaction tensor in electron paramagnetic resonance (EPR) spectroscopy. The most notable changes are found for EPR properties. The impact of the current-dependent terms rises with the number of unpaired electrons, and consequently, the EPR properties are more sensitive toward CDFT. Considerable changes are observed for the strongly constrained and appropriately normed functionals, as well as the B97M family and TASK. The current density terms are less important when exact exchange is incorporated. At the same time, the current-dependent kernel ensures the stability of response calculations in all cases. We, therefore, strongly recommend to use the framework of CDFT for self-consistent spin-orbit calculations.

Giant magneto optical properties in the double perovskites Ba2BʹRuO6 (Bʹ = Er, Tm)

This study aimed to investigate new double perovskite oxides in search of new promising functional material with properties of interest for high density storage applications. The crystal structure, magnetic, electronic and magneto-optical properties of the rare-earth-based double perovskites Ba2BʹRuO6 (Bʹ = Er, Tm) were investigated through full-potential linearized augmented plane wave method within the context of density functional theory (DFT) in Wien2k code. We used generalized gradient approximation (GGA) and GGA + U approaches to calculate magneto-optical properties, including spin–orbit coupling due to 4f and 4d-electrons. The obtained DFT-optimized structures was cubic (space group: Fm = 3m), and the calculations (GGA + U) showed that the compounds Ba2ErRuO6 is semiconductor and the Ba2TmRuO6 is half-metal. The magneto-optical Kerr effect showed pronounced peaks at angles of 17.7∘ and 5.6∘ for an energy around 0.2 eV for both compounds, which could potentially have important applications in the infrared region or for blue and violet radiation.

Relativistic versus Jahn-Teller effects in tantalum and tungsten clusters

We juxtapose the interplay of relativistic and Jahn-Teller effects in small tantalum and tungsten clusters. We employ relativistic techniques to study the low-lying electronic states of Tan for 2 ≤ n ≤ 6. We have used the complete active space MCSCF (CASSCF) techniques for the low-lying electronic states of Ta2 together with DFT techniques including spin–orbit corrections for large clusters that employed relativistic effective core potentials. The results thus obtained were compared with CASSCF/MRCI computations together with the inclusion of spin–orbit coupling for the tungsten trimer. Our computations reveal that unlike clusters containing lighter atoms, the spin–orbit effects overcome Jahn-Teller stabilization effects resulting in more symmetrical structures for tantalum and tungsten clusters. We have also computed the 3D-potential energy surfaces of different interesting regions of the Mexican hat surfaces. Whereas for the trimer and tetramer spin–orbit stabilization seems to overtake Jahn-Teller stabilization, thus resulting in the stabilization of symmetric structures, the Jahn-Teller stabilizations are larger than spin–orbit effects for larger clusters, thus resulting in distorted structures for larger clusters. We have provided a double group and graph-theoretical analysis of the electronic states of tantalum clusters to gain insights into the effect of spin–orbit coupling and pseudorotation on the electronic states of these clusters. The absorption spectra for these clusters are computed using time dependent density functional theory (TDDFT).

Spin-orbit transitions in the N+(PJA3)+H2→ NH+(X2Π,4Σ-) + H(2S) reaction, using adiabatic and mixed quantum-adiabatic statistical approaches.

The cross section and rate constants for the title reaction are calculated for all the spin-orbit states of N+(PJA3) using two statistical approaches, one purely adiabatic and the other one mixing quantum capture for the entrance channel and adiabatic treatment for the products channel. This is made by using a symmetry adapted basis set combining electronic (spin and orbital) and nuclear angular momenta in the reactants channel. To this aim, accurate ab initio calculations are performed separately for reactants and products. In the reactants channel, the three lowest electronic states (without spin-orbit couplings) have been diabatized, and the spin-orbit couplings have been introduced through a model localizing the spin-orbit interactions in the N+ atom, which yields accurate results as compared to ab initio calculations, including spin-orbit couplings. For the products, 11 purely adiabatic spin-orbit states have been determined with ab initio calculations. The reactive rate constants thus obtained are in very good agreement with the available experimental data for several ortho-H2 fractions, assuming a thermal initial distribution of spin-orbit states. The rate constants for selected spin-orbit JA states are obtained, to provide a proper validation of the spin-orbit effects to obtain the experimental rate constants.

Multidimensional dissipative solitons and solitary vortices

This article offers a review of (chiefly, theoretical) results for self-trapped states (solitons) in two- and three-dimensional (2D and 3D) models of nonlinear dissipative media. The existence of such solitons requires to maintain two stable balances: between nonlinear self-focusing and linear spreading (diffraction and/or dispersion) of the physical fields, and between losses and gain in the medium. Due to the interplay of these conditions, dissipative solitons exist, unlike solitons in conservative models, not in continuous families, but as isolated solutions (attractors). The main issue in the theory is stability of multidimensional dissipative solitons, especially ones with embedded vorticity. First, stable 2D dissipative solitons are presented in the framework of the complex Ginzburg–Landau equation with the cubic–quintic nonlinearity, which combines linear loss, cubic gain, and quintic loss (the linear loss is necessary to stabilize zero background around dissipative solitons, while the quintic loss provides for the global stability of the setting). In addition to fundamental (zero-vorticity) solitons, stable spiral solitons produced by the CGL equation are produced too, with intrinsic vorticities S=1 and 2. Stable 2D solitons were also found in a system built of two linearly-coupled optical fields, with linear gain acting in one and linear loss, which plays the stabilizing role, in the other. In this case, the inclusion of the cubic loss (without quintic terms) is sufficient for the creation of stable fundamental and vortical dissipative solitons in the linearly-coupled system. In addition to truly localized states, weakly localized ones are presented too, in the single-component model with nonlinear losses, which does not include explicit gain. In that case, the losses are compensated by the influx of power from the reservoir provided, at the spatial infinity, by the weakly localized structure of the solution. Other classes of 2D models which are considered in this review make use of spatially modulated loss or gain to predict many species of robust dissipative solitons, including localized dynamical states featuring complex periodically recurring metamorphoses. Stable fundamental and vortical solitons are also produced by models including a trapping or spatially periodic potential. In the latter case, the consideration addresses 2D gap dissipative solitons as well. 2D two-component dissipative models including spin–orbit coupling are considered too. They give rise to stable states in the form of semi-vortex solitons, with vorticity carried by one component. In addition to the 2D solitons, the review includes 3D fundamental and vortical dissipative solitons, stabilized by the cubic–quintic nonlinearity and/or external potentials. Collisions between 3D dissipative solitons are considered too.

Thickness and defect dependent electronic, optical and thermoelectric features of hbox {WTe}_2

Transition metal dichalcogenides (TMDs) receive significant attention due to their outstanding electronic and optical properties. In this study, we investigate the electronic, optical, and thermoelectric properties of single and few layer hbox {WTe}_2 in detail utilizing first-principles methods based on the density functional theory (DFT). Within the scope of both PBE and HSE06 including spin orbit coupling (SOC), the simulations predict the electronic band gap values to decrease as the number of layers increases. Moreover, spin-polarized DFT calculations combined with the semi-classical Boltzmann transport theory are applied to estimate the anisotropic thermoelectric power factor (Seebeck coefficient, S) for hbox {WTe}_2 in both the monolayer and multilayer limit, and S is obtained below the optimal value for practical applications. The optical absorbance of hbox {WTe}_2 monolayer is obtained to be slightly less than the values reported in literature for 2H TMD monolayers of hbox {MoS}_2, hbox {MoSe}_2, and hbox {WS}_2. Furthermore, we simulate the impact of defects, such as vacancy, antisite and substitution defects, on the electronic, optical and thermoelectric properties of monolayer hbox {WTe}_2. Particularly, the Te-hbox {O}_2 substitution defect in parallel orientation yields negative formation energy, indicating that the relevant defect may form spontaneously under relevant experimental conditions. We reveal that the electronic band structure of hbox {WTe}_2 monolayer is significantly influenced by the presence of the considered defects. According to the calculated band gap values, a lowering of the conduction band minimum gives rise to metallic characteristics to the structure for the single Te(1) vacancy, a diagonal Te line defect, and the Te(1)-hbox {O}_2 substitution, while the other investigated defects cause an opening of a small positive band gap at the Fermi level. Consequently, the real (varepsilon _1(omega )) and imaginary (varepsilon _2(omega )) parts of the dielectric constant at low frequencies are very sensitive to the applied defects, whereas we find that the absorbance (A) at optical frequencies is less significantly affected. We also predict that certain point defects can enhance the otherwise moderate value of S in pristine hbox {WTe}_2 to values relevant for thermoelectric applications. The described hbox {WTe}_2 monolayers, as functionalized with the considered defects, offer the possibility to be applied in optical, electronic, and thermoelectric devices.

Monte Carlo simulations of spin transport in nanoscale transistors: temperature and size effects

Spin-based metal-oxide-semiconductor field-effect transistors (MOSFETs) with a high-mobility III-V channel are studied using self-consistent quantum corrected ensemble Monte Carlo device simulations of charge and spin transport. The simulations including spin–orbit coupling mechanisms (Dresselhaus and Rashba coupling) examine the electron spin transport in the 25 nm gate length MOSFET. The transistor lateral dimensions (the gate length, the source-to-gate, and the gate-to-drain spacers) are increased to investigate the spin-dependent drain current modulation induced by the gate from room temperature of 300 K down to 77 K. This modulation increases with increasing temperature due to increased Rashba coupling. Finally, an increase of up to 20 nm in the gate length, source-to-gate, or the gate-to-drain spacers increases the spin polarization and enhances the spin-dependent drain current modulation at the drain due to polarization-refocusing effects.

Ab-initio study of the electronic structure of LaF including spin-orbit coupling.

Spectroscopic investigation of lanthanum monofluoride molecule LaF is carried out by ab-initio methods and all the observed band systems are predicted through the fine structure of LaH. This structure consisted of 67 Ω(±) states is calculated by taking into account the spin-orbit coupling effect of lanthanum. Therefore, these Ω(±) states are degenerated from 33 low-lying 1,3Λ(±) states below 33,200cm-1. The potential energy curves (PECs) of 1,3Λ(±) and Ω(±) states are displayed in the range of internuclear distance from 1.40 to 3.00Å and their spectroscopic constants ([Formula: see text],[Formula: see text], [Formula: see text], [Formula: see text]) are reported. Moreover, the permanent and the transition dipole moments are plotted as a function of internuclear distance. Furthermore, the composition of the Ω(±) state-wave functions in terms of Λ-S parent states is calculated at the equilibrium internuclear distance of the ground state. Furthermore, through calculating the splitting energy between the spin-orbit components of a 3Λ(±) state, Hund's case of many states involved in the observed band systems is determined.

Band inversion in Bi2Se3 from fat band analysis

Bi2Se3 is an established thermoelectric material and has been gaining recent popularity as a topological insulator. This study explores the topological property of Bi2Se3 by performing first principles calculation on Bi2Se3 bulk system and employing the technique of fat band analysis from the projected density of states to visualize the band inversion. Electronic band structures of Bi2Se3 are compared for two cases: before and after including spin–orbit coupling (SOC) and a slight increase in bandgap is observed. Density of states and projected density of states are calculated and compared for both the cases. Band parity analysis suggested by Fu and Kane is employed to establish the strong topological invariant number of Bi2Se3.Therefore this study is aimed at understanding the tell-tale signs of a topological insulator from first principles calculation.

The Electronic Structure of Cs2AgBiBr6 at Room Temperature

Cs2AgBiBr6 is a stable halide double perovskite with a bandgap of about 2.2 eV. Therefore, it is intensively studied as a potential lead‐free alternative to hybrid perovskite solar cell absorber materials such as methylammonium lead iodide. However, power conversion efficiencies of solar cells with this material have not yet exceeded 3%. A detailed understanding of the electronic structure of this material is difficult, due to the variance of reported data and experimental as well as theoretical difficulties that occur in going beyond a qualitative understanding of such an indirect semiconductor at device operation temperature. Herein, self‐energy‐corrected electronic structure theory including spin–orbit coupling and structural dynamics at room temperature are combined to model and understand this compound in a quantitative manner as compared with experimental findings. It is proposed that the observed low power conversion efficiencies are intrinsic and can be attributed to the density of states in the conduction band region.