Generalized Gradient Approximation Research Articles

Ab initio calculations of electric field gradients in H-bond rich molecular crystals with nearly experimental accuracy.

Ab initio calculations of electric field gradients (EFGs) in molecular crystals have advanced significantly due to the gauge including projector augmented wave (GIPAW) formalism, which accounts for the infinite periodicity in crystals. However, theoretical accuracies still lag behind experimental ones, making it challenging to distinguish experimentally distinguishable similar structures, a deficiency largely attributed to the limitation of GIPAW codes to generalized gradient approximation (GGA) density functional theory (DFT) functionals. In this study, we investigate whether hybrid DFT functionals can enhance the EFG calculation accuracy and the associated geometry optimization. Using the many-body expansion method, we focus on nitrogen EFGs in amino acids with complex H-bonding, which are often poorly described with GGA functionals. Our results show that both functionals provide highly accurate calculations that surpass current studies and approach experimental precision. The accuracies are also almost three times higher than available GIPAW/GGA calculations in the literature. However, we show that this difference is not due to the GGA functional but rather due to the improper selection of the nitrogen quadrupole moment.

Dispersionless Nonhybrid Density Functional.

A dispersion-corrected density functional theory (DFT+D) method has been developed. It includes a nonhybrid dispersionless generalized gradient approximation (GGA) functional paired with a literature-parametrized dispersion function. The functional's 9 adjustable parameters were optimized using a training set of 589 benchmark interaction energies. The resulting method performs better than other GGA-based DFT+D methods, giving a mean unsigned error of 0.33 kcal/mol. It even performs better than some more expensive meta-GGA or hybrid dispersion-corrected functionals. An important advantage of using the new functional is that its dispersion energy given by the D component is very close to the true dispersion energy at all intermolecular separations, whereas in other similarly accurate DFT+D approaches, such a dispersion contribution in the van der Waals minimum region is only a small fraction of the true value.

Density functional theory study of hydrogen and oxygen reactions on NiO(100) and Ce doped NiO(100).

This study aims to reveal the reaction mechanisms of H2 and O2 on the NiO(100) and Ce-doped NiO(100) surfaces using the density functional theory (DFT) combined with the on-site Coulomb correction (DFT + U) method. It was found that H2 and O2 react favorably on the reduced surfaces of both materials. However, after the oxygen vacancy is filled, the activation energy for the reaction between H₂ and lattice oxygen increases. Ce doping reduces this activation energy to 1.64eV (compared to 3.16eV for pure NiO(100)). The enhanced activity of lattice oxygen due to Ce doping is attributed to the charge transfer in the Ce-O bond, which leads to the electronic localization around O atoms and weakens the activation energy barrier. Moreover, the presence of Ce facilitates the formation of a sub-stable OH intermediate on the reduced surface, ensuring the sustainability of the reaction. This study provides a theoretical basis for the design of high-performance nickel-based hydrogen deoxidizers and contributes to promoting the research and development process of nickel-based catalysts in related fields. The calculations were performed using the Vienna ab initio simulation package (VASP) module of the MedeA® software. The exchange-correlation energy calculations are performed using the Perdew, Burke and Ernzerhof (PBE) functional within the generalized gradient approximation (GGA). The transition states were calculated using the MedeA® Transition State Search Module, based on the climbing-image nudged elastic band (CI-NEB) method.

Study on the modulation mechanism of the optoelectronic properties based on common electrode metal atom adsorption on graphene/MoTe2.

The two-dimensional graphene/MoTe2 heterostructure holds extensive potential applications in optoelectronic devices, sensors, and catalysts. To expand its optical applications, this study systematically investigates the adsorption stability of metal atoms (Au, Pt, Pd, and Fe) on the graphene/MoTe2 and their influence on its optoelectronic properties employing first-principles methods. The findings indicate that after the adsorption of Au and Pd, the structure retains its direct bandgap properties, while the adsorption of Pt and Fe exhibits indirect bandgap characteristics. The work functions for all adsorbed structures are lower compared to the pristine graphene/MoTe2. The total density of states is primarily derived from the C-2p, Mo-4d, Te-5p orbitals, as well as the d and s orbitals of the adsorbed atoms. The pristine graphene/MoTe2 exhibits significant absorption in the ultraviolet range. Once graphene/MoTe2 is adsorbed by metal atoms, it can significantly enhance the optical absorption across the spectrum from infrared to ultraviolet light. These findings provide important theoretical guidance for regulating the application of graphene/MoTe2 in optoelectronics and related fields. All analyses are grounded in density functional theory first principles and computed using CASTEP. Graphene/MoTe2 consists of 4 × 4 × 1 single-layer, graphene single layer, and 3 × 3 × 1 single-layer MoTe2. To prevent interactions between neighboring unit cells, a 20Å vacuum space in the z-direction is employed. The electronic exchange-correlation interactions are treated using the Perdew-Burke-Ernzerhof functional within the framework of the generalized gradient approximation. Van der Waals (vdW) interactions are incorporated using the vdW correction function proposed by Grimme, which effectively describes vdW interactions. During the simulation, the cutoff energy for plane wave expansion is set to 420eV, and the k-point grid is set to 4 × 4 × 1. The atomic displacement convergence standard is 0.002Å, the internal stress convergence standard is 0.1GPa, and the interaction force convergence standard between atoms is 0.05eV/Å. The convergence threshold for the iteration precision is set to ensure that the total energy for each atom is not less than 2 × 10-5eV/atom.

Theoretical exploration of structural, electronic, elastic, mechanical, and thermodynamic properties of MgCu4Sn intermetallic compound for engineering applications: first-principle calculations

The structural, electronic, elastic, mechanical, and thermodynamic properties of the ternary MgCu4Sn intermetallic compound are investigated by means of first-principle calculations within density functional theory (DFT), in combination with the quasi-harmonic Debye model. Local density approximation (LDA) and generalized gradient approximation (GGA) are made for electronic exchange–correlation potential energy. The lattice constant is in good agreement with experimental data. We determine the elastic constant tensor of the compound from the calculated stress–strain relation in both approximations. Once the elastic constants are obtained, the bulk modulus B, shear modulus G, Young’s modulus E, Poisson’s ratio ν, anisotropy factor A, and the ratio B/G for MgCu4Sn compound were deduced using Voigt-Reuss-Hill (VRH) approximation. The ground-state structure of MgCu4Sn is predicted to be thermodynamically and mechanically stable. The obtained band structure and density of states reveal metallic character of MgCu4Sn. The calculation results show also that this intermetallic crystal is a stiff, elastically anisotropic and ductile material. The Debye temperature is also determined from elastic constants. The temperature dependence of the constant volume heat capacity Cv, the entropy S, and the volumetric thermal expansion coefficient α in a quasi-harmonic approximation have been obtained from calculated energy E as a function of the volume V of a MgCu4Sn crystal and discussed for the first report.

A cross-entropy corrected hybrid multiconfiguration pair-density functional theory for complex molecular systems

Hybrid density functionals, such as B3LYP and PBE0, have achieved remarkable success by substantially improving over their parent methods, namely Hartree-Fock and the generalized gradient approximation, and generally outperforming the second-order Møller-Plesset perturbation theory (MP2) that is more expensive. Here, we extend the linear scheme of hybrid multiconfiguration pair-density functional theory (HMC-PDFT) by incorporating a cross-entropy ingredient to balance the description of static and dynamic correlation effects, leading to a consistent improvement on both exchange and correlation energies. The B3LYP-like translated on-top functional (tB4LYP) developed along this line not only surpasses the accuracy of its parent methods, the complete active space self-consistent field (CASSCF) and the original MC-PDFT functionals (tBLYP and tB3LYP), but also outperforms the widely used complete active space second-order perturbation theory (CASPT2). Remarkably, while remaining satisfactory for general purpose, tB4LYP shows superior accuracy for challenging cases like the Cr2 dissociation and the associated low-lying vibrational energies, the ethylene torsional rotation and the ethyne diabatic colinear dissociations, with the significantly lower computational cost than CASPT2.

Structural, electronic, mechanical, optical and magnetic properties of RhNbZ (Z = Li, Si, As) Half-Heusler compounds: a first-principles study

Abstract Structural, mechanical, electronic, optical and magnetic properties of the cubic RhNbZ (Z = Li, Si, As) half-Heusler compounds is reported using density functional theory (DFT) as implemented in quantum espresso simulation package. Structurally, the compounds are most stable when they are in type I atomic arrangement. Studies of mechanical properties indicate that all the three compounds are ductile in nature and mechanically stable. Calculations of electronic band structure and density of states (DOS) affirm that RhNbSi is a semi-conductor with an indirect band gap of 0.662 eV and 1.0095 eV from generalized gradient approximation (GGA) and GGA+U approaches respectively, where U is Hubbard parameter, RhNbLi has metallic property under both GGA and GGA+U approaches whereas RhNbAs has metallic nature under GGA prediction but it has half-metallic property under GGA+U approach, a property which is essential for spintronic applications. Optical parameters such as dielectric function, reflectivity, refractive index, extinction coefficient, absorption coefficient, optical conductivity and electron energy loss were estimated in the photon energy range of 0–40 eV. Results from these properties calculations reveal that both absorption coefficient and optical conductivity have maximum values whereas electron energy loss has minimum value in the lower energy ranges which show that the materials under our study can be considered as potential candidates for optoelectronic applications. From magnetic property calculations, RhNbSi is predicted to be nonmagnetic material but RhNbLi and RhNbAs have magnetic nature.

Structural, electronic and optical properties of SrMnO3 photocatalyst for dye degradation; experimental and DFT study

Perovskite oxides (PO) are versatile multi-functional materials with wide range of applications. In current study, highly-crystalline perovskite manganite (PM) SrMnO3 has been synthesized via ultrasonic method followed by calcination at 600 °C. Morphology of PM with irregular shape and size was assessed by FESEM and hexagonal geometry with a crystallite size of 13.67nm was determined by XRD studies. As-synthesized PM was further tested as photocatalyst for its dye degradation potential against malachite green (MG) and methylene blue (MB). In the presence of synthesized perovskites, degradation of both the dyes MG and MB was achieved in 12min and 4.5min with the percentage degradation of 80.26% and 89.35% respectively. The factors including pH and temperature affecting degradation of both the dyes were also studied. Additionally, calculations based on simulated DFT (density function theory) have been employed to explore the optical, electronic and structural attributes of SrMnO3 PM through generalized gradient approximation (GGA). The total and partial density of states have been evaluated by GGA confirms the Fermi level (Ef) characteristics of metallic Sr and Mn and found that ‘d’ and ‘p’ orbitals of Sr, Mn and O were responsible for the band formation. The results of the current study advocate the synthesis of PM and related compounds followed by their successful applications as catalyst for dye degradation as well as many other fields involving the use of nanomaterials.

Accurate predictions of chemical shifts with the rSCAN and r2SCAN mGGA exchange-correlation functionals.

We benchmark the rSCAN and r2SCAN exchange-correlation functionals by comparing the Nuclear Magnetic Resonance (NMR) magnetic shieldings predicted by Density Functional Theory (DFT) to experimentally observed chemical shifts of halide and oxide inorganic compounds. Significant improvement in accuracy is achieved compared to the Generalised Gradient Approximation (GGA) at a marginally higher computational cost. When using rSCAN or r2SCAN, the correlation coefficient between computationally predicted and experimental values approaches the theoretically expected value of -1 while reducing the deviation, allowing more accurate and reliable spectrum assignments of complex compounds in experimental investigations.

The interplay of density functional selection and crystal structure for accurate NMR chemical shift predictions.

Ab initio chemical shift prediction plays a central role in nuclear magnetic resonance (NMR) crystallography, and the accuracy with which chemical shifts can be predicted relative to experiment impacts the confidence with which structures can be assigned. For organic crystals, periodic density functional theory calculations with the gauge-including projector augmented wave (GIPAW) approximation and the PBE functional are widely used at present. Many previous studies have examined how using more advanced density functionals can increase the accuracy of predicted chemical shifts relative to experiment, but nearly all of those studies employed crystal structures that were optimized with generalized-gradient approximation (GGA) functionals. Here, we investigate how the accuracy of the predicted chemical shifts in organic crystals is affected by replacing GGA-level PBE-D3(BJ) crystal geometries with more accurate hybrid functional PBE0-D3(BJ) ones. Based on benchmark data sets containing 132 13C and 35 15N chemical shifts, plus case studies on testosterone, acetaminophen, and phenobarbital, we find that switching from GGA-level geometries and chemical shifts to hybrid-functional ones reduces 13C and 15N chemical shift errors by ∼40-60% versus experiment. However, most of the improvement stems from the use of the hybrid functional for the chemical shift calculations, rather than from the refined geometries. In addition, even with the improved geometries, we find that double-hybrid functionals still do not systematically increase chemical shift agreement with experiment beyond what hybrid functionals provide. In the end, these results suggest that the combination of GGA-level crystal structures and hybrid-functional chemical shifts represents a particularly cost-effective combination for NMR crystallography in organic systems.

A hybrid meta on-top functional for multiconfiguration pair-density functional theory

Multiconfiguration pair-density functional theory (MC-PDFT) was proposed a decade ago, but it is still in the early stage of density functional development. MC-PDFT uses functionals that are called on-top functionals; they depend on the density and the on-top pair density. Most MC-PDFT calculations to date have been unoptimized translations of generalized gradient approximations (GGAs) of Kohn-Sham density functional theory (KS-DFT). A hybrid MC-PDFT has also been developed, in which one includes a fraction of the complete active space self-consistent-field wave function energy in the total energy. Meta-GGA functionals, which use kinetic-energy densities in addition to GGA ingredients, have shown higher accuracy than GGAs in KS-DFT, yet the translation of meta-GGAs has not been previously proposed for MC-PDFT. In this paper, we propose a way to include kinetic energy density in a hybrid on-top functional for MC-PDFT, and we optimize the parameters of the resulting functional by training with a database developed as part of the present work that contains a wide variety of systems with diverse characters. The resulting hybrid meta functional is called the MC23 functional. We find that MC23 has improved performance as compared to KS-DFT functionals for both strongly and weakly correlated systems. We recommend MC23 for future MC-PDFT calculations.

Computational insights into the impact of co-doping and induced pressure on magnetic switching properties of multiferroic for data transfer

Abstract Bismuth ferrite BiFeO3 (BFO) stands out as one of the most extensively researched multiferroic materials due to its magnetoelectric switching behavior. First-principles analysis within generalized gradient approximation plus Hubbard U (GGA+U) was employed to investigate the effects of lanthanum (La) doping at the A-site and nickel (Ni) doping at the B-site, as mono- and co-dopants, on spin-polarized electronic, structural, and magnetic properties for magnetic switching. The lattice constant and volume of BFO decrease linearly with increasing pressure. BFO in its cubic phase with space group Pm-3m typically exhibits metallic behaviour. However, the semiconducting nature of BFO in cubic phase has been observed, accompanied by enhanced magnetism (8.73 × 104 A m−1), strong magnetoelectric coupling (1.82 × 10−7 m−1sec) and a colossal value of magnetic force (1.82 T) at 60 GPa pressure. In Ni-substituted BFO structure, a large magnetization of 7.83 × 104 A m−1 and a linear magnetoelectric coupling coefficient of 1.64 × 10−8 sec m−1 and a remarkably high magnetic force of 1.64 T were observed, which is suitable for data transfer applications.

Study of the Gravimetric, Electronic and Thermoelectric Properties of XAlH3 (X = Be, Na, K) as hydrogen storage perovskite using DFT and the BoltzTrap Software Package

In the context of density functional theory (DFT), this study examines the structural, electronic, gravimetric and thermoelectric properties of perovskite compounds XAlH3 (X = Be, Na and K) using the generalized gradient approximation (GGA). Calculations were performed with the BoltzTrap software package integrated into the Wien2k code, enabling analysis of total energy and atomic volume using the Murnaghan equation of state. The results show that the materials behave like conductors due to the overlap of the conduction band and the valence band, with a zero band gap. NaAlH3 and KAlH3 show increasing electrical and thermal conductivity with temperature, while BeAlH3 exhibits non-linear behavior, peaking at 400 K. These results suggest that XAlH3 materials are promising for hydrogen storage applications and thermoelectric devices, underlining their potential to support a sustainable hydrogen economy.

The Impact of Carbon on Electronic Structure of N-Doped ZnO Films: Scanning Photoelectron Microscopy Study and DFT Calculations.

A Scanning Photoelectron Microscopy (SPEM) experiment has been applied to ZnO:N films deposited by Atomic Layer Deposition (ALD) under O-rich conditions and post-growth annealed in oxygen at 800 °C. State-of-the-Art spatial resolution (130 nm) allows for probing the electronic structure of single column of growth. The samples were cleaved under ultra-high vacuum (UHV) conditions to open atomically clean cross-sectional areas for SPEM experiment. It has been shown that different columns reveal considerably different shape of the valence band (VB) photoemission spectra and that some of them are shifted towards the bandgap. The shift of the VB maximum, which is associated with hybridization with acceptor states, was found to be correlated with carbon content measured as a relative intensity of the C1s and Zn3d core levels. Generalized Gradient Approximation (GGA) supplemented by +U correction was applied to both Zn3d and O2p orbitals for calculation of the VZn migration properties by the Nudged Elastic Band (NEB) method. The results suggest that interstitial -CHx groups facilitate the formation of acceptor complexes due to additional lattice perturbation.

Skyrmions and Fluctuations of Spin Spirals in Strongly Correlated Fe1–хCoхSi with Noncentrosymmetric Cubic Structure

Strongly correlated Fe1–хCoxSi solid solutions with broken B20-type cubic structure are studied. Within the framework of the spin-fluctuation theory and in the model of the density of electronic states, arising from first-principles calculations within the framework of the generalized gradient approximation taking into account strong Coulomb correlations (GGA+U) temperature transitions are considered in strongly correlated Fe1–хCoxSi alloys (for example, x = 0.2, 0.3) with the Dzyaloshinskii–Moriya (DM) interaction. It is shown that in the compositions under consideration, a first-order magnetic phase transition, which is prolonged in temperature, occurs, during which the sign of the intermode coupling parameter in the Ginzburg–Landau functional changes. It is found that such a transition results in the formation of skyrmion A-phases in limited ranges of temperatures and external magnetic fields, beyond which the experimentally observed fluctuations of spin spirals are realized. The constructed (h–Т)-diagrams (which indicate the range of long-range order, fluctuation and skyrmion phases) of Fe1–хCoxSi at x = 0.2 and 0.3 are consistent with the experiment.

Integrating Experimental and Computational Insights: A Dual Approach to Ba2CoWO6 Double Perovskites

Double perovskite materials have emerged as key players in the realm of advanced materials due to their unique structural and functional properties. This research mainly focuses on the synthesis and comprehensive characterization of Ba2CoWO6 double perovskite nanopowders utilizing a high-temperature conventional solid-state reaction technique. The successful formation of Ba2CoWO6 powders was confirmed through detailed analysis employing advanced characterization techniques. Rietveld refinement of X-ray diffraction (XRD) and Raman data established that Ba2CoWO6 crystallizes in a cubic crystal structure with the space group Fm-3m, indicative of a highly ordered perovskite lattice. The typical crystallite size, approximately 65 nm, highlights the nanocrystalline nature of the material. Scanning Electron Microscopy (SEM) and Transmission Electron Microscopy (TEM) discovered a distinctive morphology characterized by spherical shaped particles, suggesting a complex particle formation process influenced by synthesis conditions. To probe the electronic structure, X-ray Photoelectron Spectroscopy (XPS) identified cobalt and tungsten valence states, critical for understanding dielectric properties associated with localized charge carriers. The semiconducting character of the synthesized Ba2CoWO6 nanocrystalline material was confirmed through UV-Visible analysis, which revealed an energy bandgap value of 3.3 eV, which aligns well with the theoretical predictions, indicating the accuracy and reliability of the experimental results. The photoluminescence spectrum exhibited two distinct emissions in the blue-green region. These emissions were attributed to the transitions 3P0→3H4, 3P0→3H5, and 3P0→3H6, primarily resulting from the contributions of Ba2+ ions. The dielectric characteristics of the compound were analyzed across a different range of frequencies, spanning from 1 kHz to 1 MHz. Magnetic characterization using Vibrating Sample Magnetometry (VSM) revealed antiferromagnetic behavior of Ba2CoWO6 ceramics at room temperature, attributed to super-exchange interactions between Co3+ and W5+ ions mediated by oxygen ions in the perovskite lattice. Additionally, first-principles calculations based on the Generalized Gradient Approximation (GGA+U) with a modified Becke–Johnson (mBJ) potential were employed to gain a deeper understanding of the structural and electronic properties of the materials. This approach involved systematically varying the Hubbard U parameter to optimize the description of electron correlation effects. These results deliver an extensive understanding of the structural, optical, morphological, electronic, and magnetic properties of Ba2CoWO6 ceramics, underscoring their potential for electronic and magnetic device applications.

Data-Efficient Multifidelity Training for High-Fidelity Machine Learning Interatomic Potentials.

Machine learning interatomic potentials (MLIPs) are used to estimate potential energy surfaces (PES) from ab initio calculations, providing near-quantum-level accuracy with reduced computational costs. However, the high cost of assembling high-fidelity databases hampers the application of MLIPs to systems that require high chemical accuracy. Utilizing an equivariant graph neural network, we present an MLIP framework that trains on multifidelity databases simultaneously. This approach enables the accurate learning of high-fidelity PES with minimal high-fidelity data. Employing the generalized gradient approximation (GGA) and meta-GGA as low- and high-fidelity approaches, respectively, we tested this framework on the Li6PS5Cl and InxGa1-xN systems. The results show that using a high-fidelity training set with a size approximately 10% of the low-fidelity set, the multifidelity training framework achieves excellent accuracy, with Li-ion conductivity predictions within 10% error and InxGa1-xN mixing energy showing an R2 of 0.98 compared to the reference high-fidelity MLIP results. It indicates that geometric and compositional spaces not covered by the high-fidelity meta-GGA database can be effectively inferred from low-fidelity GGA data, thus enhancing accuracy and molecular dynamics stability. We also developed a general-purpose MLIP that utilizes both GGA and meta-GGA data from the Materials Project, significantly enhancing MLIP performance for high-accuracy tasks such as predicting energies above hull for crystals in general. Furthermore, we demonstrate that the present multifidelity learning is more effective than transfer learning or Δ-learning and that it can also be applied to learn higher-fidelity up to the coupled-cluster level. We believe this methodology holds promise for creating highly accurate bespoke or universal MLIPs by effectively expanding the high-fidelity data set.

Computational Insights into the Stability, Mechanical, Optoelectronic, and Thermoelectric Characteristics Investigation on Lead‐Based Double Perovskites of (Cs2, K2, Rb2)PbCl6: Promising Candidates for Optoelectronic Applications

AbstractLead‐based double perovskites are studied in the cubic phase using the generalized gradient approximation and the modified Becke–Johnson (mBJ‐GGA) functionals as implemented in the Wien2K code. Goldschmidt tolerance factor and octahedral factor, formation enthalpy, and formation energy translate the structural, chemical, and thermodynamic stability of double perovskites studied. Phonon band structures and elastic moduli ensure the dynamic and mechanical stability of (Cs2, K2, Rb2)PbCl6. An intermediate band appears in the conduction band and the fundamental transition takes place between 3p‐Cl state and 6p‐Pb site. The refractive index of double perovskites (Cs2, K2, Rb2)PbCl6 in the visible and ultraviolet light hold a huge advantage for solar cell applications. The wide dielectric constant of double perovskites under study makes them capable for absorbing energy between 1 and 5 eV, and are suitable for solar power applications. (Cs2, K2, Rb2)PbCl6 have positive Seebeck coefficient, which reveals that p‐type charge carriers are dominant for enhancing their performance. Cs2PbCl6 has positive thermal conductivity for both n‐type and p‐type character. (K2, Rb2)PbCl6 have positive thermal conductivity for n‐type character. The complete analysis reveals that they are potentially significant candidates for future solar cells and energy harvesting devices.

CoTCNQ as a Catalyst for CO2 Electroreduction: A First Principles r2SCAN Meta-GGA Investigation.

Using first principles calculations we investigate cobalt-coordinated tetracyanoquinodimethane (R-CoTCNQ) as a potential catalyst for the CO2 electroreduction reaction (CO2ERR). We determine that exchange-correlation functionals beyond the generalized gradient approximation (GGA) are required to accurately describe the spin properties of R-CoTCNQ, therefore, the meta-GGA r2SCAN functional is used in this study. The free energy CO2ERR reaction pathways are calculated for the reduced catalyst ([R-CoTCNQ]-1e) with reaction products HCOOH and HCHO predicted depending on our choice of electrode potential. Calculations are also performed for [R-CoTCNQ]-1e supported on a H-terminated diamond (1 1 0) surface with reaction pathways being qualitatively similar to the [R-CoTCNQ]-1e monolayer. The inclusion of boron-doping in the diamond support shows a slightly improved CO2ERR reaction pathway. Furthermore, structurally, supported R-CoTCNQ provide a high specific area of active Co active sites and could be promising catalysts for future experimental consideration.

Ab Initio Investigation of the Mechanics and Thermodynamics of the Cubic EuAlO3 and GdAlO3 Perovskites for Optoelectronic Applications

Perovskites are currently becoming common in the field of optoelectronics, owing to their promising properties such as electrical, optical, thermoelectric, and electronic. Although mechanical and thermal properties also play a crucial part in the functioning of the optoelectronic devices, they have scarcely been explored. The present work performed an ab initio study of the mechanical and thermal properties of the cubic EuAlO3 and GdAlO3 perovskites for the first time using density functional theory. Quantum Espresso and Themo_pw codes were utilized by employing the generalized gradient approximation. Although the results showed that both materials have good mechanical and thermal properties that are ideal for the above–mentioned applications, EuAlO3 possessed better structural and thermal stability, bulk modulus, Poisson ratio, thermal expansion coefficient, and thermal stress; while GdAlO3 possessed better Young’s modulus and shear modulus. Moreover, the mechanical properties of the two materials turned out to be much better than those of the common materials for optoelectronic applications, while their thermal properties were comparable to that of sapphire glass. Since this study was computational, an experimental verification of the computed properties of the two materials needs to be carried out before they can be commercialized.