Chalcopyrites demonstrate compelling features for optoelectronic and photovoltaic devices, attributed to their valuable properties. Their remarkable light-absorption capabilities and well-suited band gap render them so attractive for applications in these fields. By allowing low-energy sub-bandgap photons to pass through and reducing the thermalisation loss from high-energy photons, intermediate-band materials address the primary problems in solar cells. This approach allows for more efficient use of the solar spectrum, helping solar cells exceed the traditional efficiency limits defined by the Shockley-Queisser limit. The objective of this study was to evaluate the electronic and optical characteristics of CuAlS2 systems doped with transition metals (TM = Mn, Fe) using the Full Potential Linearized Augmented Plane Wave approach within the framework of Density Functional Theory. A stable phase within the systems was observed upon replacing the Al atom with TM. The functionality of the intermediate band was governed by the 3d electronic characteristics of the TM3+ ion and its electronic configuration. The optical properties of CuAlS2 doped with Mn and Fe were analysed by calculating the dielectric function, refractive index, reflectivity, and absorption coefficient. Furthermore, the introduction of Mn and Fe through doping led to the creation of an intermediate band, enhancing visible light absorption and power conversion efficiency. Consequently, the optical spectrum of Mn-doped CuAlS2 and Fe-doped CuAlS2 compounds exhibits additional absorption peaks, accompanied by a significant improvement in absorption intensity. Our findings highlighted the need for continued and futuristic research into the scalability of these materials for practical applications in solar cells, optoelectronics, and spintronic devices. This investigation suggests that Mn-doped CuAlS2 holds the highest potential due to its high charge carriers and low recombination rate, indicating enhanced performance in CuAlS2-based intermediate band solar cells.

This paper employs the density functional theory to investigate the structural, elastic, and optoelectronic properties of chalcogenide-based perovskite CaSiX3 (X = S, Se, and Te) for potential optoelectronic applications. Using PBE-GGA and TB-mBJ approaches, the study examines lattice parameters, bulk modulus, formation energy, phonon frequencies, tolerance factor, and elastic properties to assess material stability. Optical characteristics such as complex dielectric function, absorption coefficient, refractive index, and refractivity are analyzed, along with the density of states and electronic band structure. Indirect band gap values are determined as 3.02 eV for CaSiS3, 1.71 eV for CaSiSe3, and 0.0 eV for CaSiTe3. Both CaSiS3 and CaSiSe3 exhibit high absorption in the ultraviolet spectrum (412-665 nm), indicating potential optoelectronic applications, especially as perovskite-based solar cells. These findings provide insight for future experimental research in this field.

This study aims to examine the equilibrium Kesterite structure of Cu2BeSnS4, Cu2BeSnSe4, and Cu2BeSnTe4 by the application of density functional theory (DFT) and the Full-Potential Linearized Augmented Plane Wave (FP-LAPW) method. The study demonstrates that both Cu2BeSnS4 and Cu2BeSnSe4 compounds are semiconductors with direct band gaps at the Γ point, while Cu2BeSnTe4 has an indirect band gap (Γ→X). The electronic and optical characteristics of these materials indicate their potential utility in optoelectronic, photonic, and photovoltaic applications. Furthermore, a thorough comparison has been conducted between the obtained results and other experimental and theoretical data from the same chalcogenide family. In summary, the findings offer valuable information on the possible photovoltaic uses of these compounds.

We present the results of first-principle calculations using the Vienna Ab-initio Simulation Package (VASP) for a new class of organometallics labeled TM3C6O6 (TM =Sc, Ti, V, Cr, Fe, Co, Ni and Cu) in the form of planar, two-dimensional, periodic free-standing layers. These materials, which can be produced by on-surface coordination on metallic surfaces, have a kagome lattice of TM ions. Calculating the structural properties, we show that all considered materials have local magnetic moments in the ground state, but four of them (with Fe, Co, Ni and Cu) show spin-crossover behavior by changing the lattice constant, which could be valuable for possible epitaxy routes on various substrates. Surprisingly, we find a very large richness of electronic and magnetic properties, qualifying these materials as highly promising metal-organic topological quantum materials. We find semi-conductors with nearest-neighbor ferromagnetic (FM) or antiferromagnetic (AFM) couplings for V, and Sc and Cr, respectively, being of potential interest to study spin ice or spin liquids on the 2D kagome lattice. Other TM ion systems combine AFM couplings with metallic behavior (Ti, Fe and Ni) or are ferromagnetic kagome metals like Cu3C6O6 with symmetry protected Weyl crossings at the Fermi surface. For the latter compound, the spin orbit coupling is shown to be responsible for small gaps which should allow the observation of the quantum anomalous Hall effect (QAHE).

The $GW$ approximation is a well-established method for calculating ionization potentials and electron affinities in solids and molecules. For numerous years, obtaining self-consistent $GW$ total energies in solids has been a challenging objective that is not accomplished yet. However, it was shown recently that the linearized $GW$ density matrix permits a reliable prediction of the self-consistent $GW$ total energy for molecules [F. Bruneval et. al. J. Chem. Theory Comput. 17, 2126 (2021)] for which self-consistent $GW$ energies are available. Here we implement, test, and benchmark the linearized $GW$ density matrix for several solids. We focus on the total energy, lattice constant, and bulk modulus obtained from the $GW$ density matrix and compare our findings to more traditional results obtained within the random phase approximation (RPA). We conclude on the improved stability of the total energy obtained from the linearized $GW$ density matrix with respect to the mean-field starting point. We bring compelling clues that the RPA and the $GW$ density matrix total energies are certainly close to the self-consistent $GW$ total energy in solids if we use hybrid functionals with enriched exchange as a starting point.

The supramolecular self-assembly of s-indacene-1,3,5,7(2H,6H)-tetrone on the Cu(111) surface was investigated under ultrahigh vacuum by room-temperature scanning tunneling microscopy supported by theoretical modelling based on density functional theory. In total, six different phases were found, driven by hydrogen bonding, metal ligand coordination or covalent coupling. Host-guest interactions allowed for the accommodation of molecular or metal clusters inside the open nanoporous patterns. In one phase, molecular trapping was stochastically observed inside the large periodic nanopores created inside the supramolecular network. The three metal-organic networks observed resulted in the creation of different kinds of regular arrays of isolated metal adatoms or adatom clusters with a lattice period larger than 1 nm.

Pillared graphenes are stacked graphene layers separated by spacers, or "pillars", of various types and have attracted significant attention in material science. In graphene networks, the pillars are used to increase interlayer distances and control their electronic conductivity, mechanical strength, and chemical reactivity. Such materials are currently investigated for a wide range of potential applications, including optoelectronics, flexible electronics, energy storage, catalysis, and sensing. In this work, we deal with the optical behavior of a special class of these promising materials, in which graphene sheets, piled one on top of the other, are covalently connected by diamino organic molecules via carbon-nitrogen single bonds. In particular, we studied elemental molecular quantities strongly related to molecules and materials' linear and nonlinear optical profiles. Properties such as optical gaps, UV-vis absorption spectra, excited states, and the first dipole hyperpolarizabilities have been computed and analyzed within the density functional theory framework. The obtained results suggest that both the linear and the nonlinear optical profiles of graphene architectures interconnected by conventional organic diamino molecules are dominated by the optical responses of the graphene layers. On the other hand, the diamino pillars are indirectly involved, in the optical behavior of these species, through local structural modifications on the framework of the graphene sheets as a result of the cross-linking process. Specifically, the performed computations, conducted in large finite graphene flakes of specific aromaticity patterns, exposed that local structural patterns may trigger surprisingly strong variations with respect to their optical absorption profiles, excited states, and nonlinear optical behavior. Such local structural patterns involve intercyclic carbon- carbon single bonds formed between sp3-hybridized carbon atoms belonging to two neighboring aromatic sextets. As far as the nonlinear optical properties are concerned, Kohn-Sham coupled perturbed computations on systems of various cross-linking patterns showed that NLO-inactive graphene sections, in terms of quadratic nonlinear optical responses, could be converted to materials of important nonlinearities. Finally, no evident dependence of the optical absorption profiles was observed with respect to the type (aromatic, conjugated, or fully saturated) of the pillar used.

Crystal structures, electronic, and magnetic properties of RbCeX2 (X = S, Se, Te) crystals are investigated using periodic density functional theory (DFT) calculations under hydrostatic pressures up to 10 GPa. The ferromagnetic phase is slightly more stable than the anti-ferromagnetic one for all compounds and pressures. A pressure-induced transition from a magnetic semiconductor (MS) to a spin gapless semiconductor (SGS) is observed only in the case of the X = Te compound. In absence of imposed pressure, the X = Te exhibits a direct alpha-spin gap of 0.46 eV while its beta-gap is 2.30 eV. A pressure of 10 GPa completely suppresses the alpha-spin gap of RbCeTe2 and reduces it beta-gap to 1.63 eV. This pressure-induced elimination of only one spin gaps is exclusive to the X = Te compound. This property distinguishes the Te compound from its two congeners. The pressure-response characteristics of RbCeTe2 renders this compound a potential pressure induced MS -> SGS switching material. (C) 2021 Elsevier B.V. All rights reserved.

We predict two switchable one-dimensional (1D) spin-polarized semiconductors based on metal-organic coor-dination chains constructed out of Fe, V, and zwitterionic quinone (ZQ) molecules using first-principle densit y functional theoretical analysis. The Fe-ZQ coordination chain can be converted from a semiconductor to a half-metal when oxidized by chlorine (Cl). Upon chlorination, the magnetic moment of the Fe-ZQ is increased from 4 mu(B) to 5 mu(B), per iron atom. In addition, the bimetallic (Fe-ZQ-V-ZQ) ferromagnetic semiconducting coordination chain with a very sma l l energy gap of only 90 meV can be converted to an antiferromagnetic semiconductor with a large gap of more than 1 eV when oxidized by chlorine. Its magnetic moment is found to be 8 mu(B) per heter-obimetallic unit (Fe and V) after chlorination, and 7 mu(B) without chlorine. These unique properties, namely a switchable or reversible electronic and magnetic characteristics with a transition between different semi-conducting states, make these coordination chains to be highly promising candidates for specific applications as multi-functional switch in nanoelectronics and spintronics.

We report on the successful on-surface synthesis of metal-organic covalent coordination networks with a dense Kagome lattice of metallic centers. In the case of Mn centers ab-initio calculations show that the adsorbed monolayer on Ag(111) has all the characteristic features of a strictly two-dimensional (2D) ferromagnetic Kagome metal. Tetrahydroxyquinone (THQ) and metal atoms (M=Cu or Mn) are co-deposited on the Ag(111) substrate to build well-ordered 2D lattices M$_3$C$_6$O$_6$. The surface is studied by scanning tunneling microscopy (STM), low energy electron diffraction (LEED) and X-ray photoelectron spectroscopy (XPS) to optimize the growth conditions like fluxes and temperatures. The details of the atomic, electronic and magnetic structures are clarified by density functional theory (DFT) calculations. XPS and DFT reveal a Cu$^+$ charge state and no local magnetic moments for the Cu-organic network. For the Mn-organic network, we find the charge state Mn$^{2+}$ and a local spin S=5/2. Charge transfer stabilizes the Cu$^+$ and Mn$^{2+}$ charge states. We find two different modifications of the M$_3$C$_6$O$_6$ lattice. DFT calculations which neglect the small spin-orbit coupling show a Dirac point, i.e. a band crossing with linear electron dispersion at the K-point of the Brillouin zone. This Dirac point is at the Fermi level if there is no charge transfer but drops by 100 meV if electron doping of Cu$_3$C$_6$O$_6$ on Ag(111) surface is acknowledged. We predict the magnetic couplings of an isolated M$_3$C$_6$O$_6$ monolayer to be short range and antiferromagnetic leading to high frustration at the Kagome lattice and a tendency towards a spin-liquid ground state. In the case of hole transfer from the substrates ferromagnetic ordering is introduced, making M$_3$C$_6$O$_6$ an interesting candidate for the quantum anomalous Hall effect.

The on-surface synthesis of metal-organic covalent coordination networks with a dense Kagome lattice of metallic centers is reported. Tetrahydroxyquinone and metal atoms (M = Cu or Mn) are codeposited on Ag(111) substrate to build well-ordered 2D lattices M3C6O6. The surface is studied by scanning tunneling microscopy, low-energy electron diffraction, and X-ray photoelectron spectroscopy (XPS). Density functional theory (DFT) reveals a Cu+ charge state and no local magnetic moments for the Cu-organic network. For the Mn-organic network, the charge state Mn2+ and a local spin S = 5/2 are found. Charge transfer stabilizes the Cu+ and Mn2+ charge states. DFT calculations show a Dirac point, i.e., a band crossing with linear electron dispersion at the K-point (2/3)g -> a+(1/3)g -> b$(2/3){\vec{g}_a} + (1{\rm{/}}3){\vec{g}_b}$ of the Brillouin zone. This Dirac point is at the Fermi level without charge transfer but drops by 100 meV if electron doping of Cu3C6O6 on Ag(111) surface is acknowledged. The magnetic couplings of an isolated Mn3C6O6 monolayer to be short range and antiferromagnetic leading to high frustration at the Kagome lattice and a tendency toward a spin-liquid ground state are predicted. In the case of hole transfer from the substrate, ferromagnetic ordering is introduced, making Mn3C6O6 an interesting candidate for the quantum anomalous Hall effect.

This work reports for the first time theoretical third order nonlinear optical susceptibilities of YSH bulk phases which are key properties for telecommunication technologies and integrated photonic devices. Our outcomes, relying on coupled perturbed Kohn-Sham density functional theory expose that the NLO capacity of YSH should be similar to another material of this family, namely, yttria stabilized zirconia that has been proposed as a promising candidate for integrated photonics by Marcaud et al. (2020). Finally, evidence implying important vibrational contributions to the optical nonlinearities of the systems are revealed and analyzed.

Yttria-stabilized zirconia (YSZ) is a widely recognized ceramic of distinct electrical, mechanical and optical properties. Although YSZ is an intrinsically paramagnetic solid, it could potentially transform to a magnetic semiconductor by incorporating in its crystalline structure isolated atoms bearing unpaired valence electrons. Based on this hypothesis and motivated by the latest advances on YSZ doped with rare-earth atoms, in the current article we report on the electronic and magnetic properties of YSZ doped with Er3+ ([Xe]4f116s0) cations that comprise three “unpaired” 4f electrons in their ground state electronic configuration. Our computations, conducted on YSZ 6.7 mol% in Y2O3 doped with two different Er3+ concentrations (3.2 and 6.7 mol% in Er2O3), expose that Er3+:YSZ is a stable antiferromagnetic semiconductor ( $$S=\frac{3}{2}$$ per Er+3) bearing a rather wide band gap of about 5 eV. All results presented and discussed in current report rely on spin–polarized density functional theory (DFT) within the spin resolved generalized gradient approximation (SGGA) for the pure Perdew, Burke and Ernzerhof exchange–correlation functional (PBE) and hybrid version widely referred as PBE0. According to our knowledge, this is the first time that the magnetic properties of Er3+: YSZ materials are reported for any Er+3 concentration.

The electronic and magnetic properties of one-dimensional polymers of zwitterionic quinone (ZQ) molecules with 4d and 5d transition metals (TM) are studied using density functional calculations. We present the results of first-principle calculations for the electronic and magnetic properties, including the magnetic anisotropy energy (MAE) of selected 4d- and 5d-ZQ polymers, using the Vienna Ab-initio Simulation Package (VASP). In particular, a pronounced magnetic character is found for TM-ZQ polymers with the TM ions Mo, Ru, Rh, Ag, Re, and Ir, having local magnetic moments between 1 and 4 mu B and ferromagnetic or antiferromagnetic nearest neighbor exchanges. The large values of spin-orbit coupling lead to high magnetic anisotropy energies (MAE) especially for Rh-ZQ and Re-ZQ, exceeding the MAE of its 3d counterparts considerably. All investigated TM-ZQ polymer chains were found to be spin-polarized semiconductors, which make them, together with the high MAE, excellent candidate materials for spintronics.

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The structural, magnetic, electronic, and elastic properties of magnetic semiconductors RbLnSe(2) (Ln = Ce, Pr, Nd and Gd) are elucidated using density functional theory (DFT) using both large and small core pseudopotentials for the lanthanide atoms. Magnetic ordering is investigated using spin-polarized calculations, and the higher stability of ferromagnetic configuration is predicted. It is found that the splitting of 4f-Ln states drives the ferromagnetic character of these materials and that the total and partial magnetic moments increase with the energy band gap. The RbLnSe(2) compounds are found to be semiconductors with two spin band gap channels (Eg(1) and Eg(2)) in both spin directions. The band gaps of RbNdSe2 and RbGdSe2 suggest their possible usefulness in photoresponse applications. The mechanical stabilities and elastic properties of RbLnSe(2) were calculated for the single and polycrystals and reinforce the suggestion of their potential photoresponse and spintronic technological applications.

On-surface polymerization of iron atoms and zwitterion quinone (ZQ) molecules on Ag(111) is studied experimentally under ultrahigh vacuum and theoretically in the framework of density functional theory. The resulting one-dimensional (1D) polymer chain is a promising model system to study both magnetic and conductive properties in one dimension. Previously we have shown that such polymer synthesis is possible over large scale by a controlled codeposition of the two elements (i.e., metal and molecule) on a Ag(111) substrate (Nano Res. 2017, 10, 933). In that case, polymer chains are bound together to form a two-dimensional (2D) arrangement of spin chains influencing the magnetic properties of individual chains. Here we show that individual chains can be obtained using a sequential deposition of first metals and then ligands by scanning tunnelling microscopy on the Ag(111) surface. Ab initio calculations are used to compare the atomic, electronic, and magnetic structures of isolated Fe-ZQ polymer chains (1D) to the previously obtained two-dimensional (2D) arrangement of the polymer chains. The adsorption energy is determined using the spin-polarized generalized gradient approximation (SGGA) and the SGGA+U approximation. It yields small values of less than 530 meV per Fe. On the Ag(111) surface, the most favorable adsorption site of Fe in the polymer chain is the hexagonal close-packed (hcp) site for the 1D polymer, but it changes to the face-centered-cubic (fcc) site for the 2D polymer. Using both SGGA and SGGA+U methods, we find a small difference between the two sites: face-centered-cubic (fcc) and hexagonal-close-packed (hcp). This latter is the most stable adsorption energy when we add the Hubbard U term to the SGGA method.

The synthesis and optoelectronics properties of polyaromatic hydrocarbons (PAHs) doped with boron and nitrogen units (BN) monopolize the interest of increasing numbers of researchers the past few years. The key concept fueling these attempts lies on the prospect of engineering novel organic compounds of versatile physical and chemical properties using well-known all-carbon systems as scaffolds. Among the various BN-doped PAHs synthesized so far, one could distinguish two categories. The most common one comprises systems in which BN units replace aromatic CC bonds. The second one, which this study deals with, refers to systems wherein the BN unit replaces intercyclic CC bonds linking two independent aromatic sextets within the framework of a given PAH. In this work, starting from a reference molecule belonging to the latter category, namely, the pyridine-adduct of borazine, we open the subject of PAHs doped with intercyclic boron nitrogen bonds. Our results, based on state-of-the-art ab initio and density functional theory wavefunction methods, suggest that intercyclic BN bonds, referred in the literature as "N -> B dative bonds", if successfully incorporated to (in)finite polyaromatic sections, may alter the optical absorption profiles of the parental systems in a greater extent than typical BN aromatic units. Specifically, we predict and comprehensively interpret the capacity of N -> B dative bonds to switch-on extra-strong one- and two-photon quantum transitions followed by intense transfer of charge. The strong excited-states alternation triggered by the presence of N -> B dative bonds may unleash exceptionally high nonlinear optical responses and could find a proper ground in organic optoelectronic technologies.

Ab initio calculations based on density functional theory (DFT) including an explicit treatment of the strong electron correlation in the d shell of the transition metal ions have been conducted us...