Negative Formation Energy Research Articles

Novel Prediction Using TB-mBJ of Electronic Properties, Magnetic Exchange Couplings, and Half-Metallicity in CrCaSe Materials

In this study, we have performed investigations on the structural stability, elec-tronic band structures, magnetic exchange couplings, and half-metallic performance of CrxCa1-xSe materials using computational methods of density functional theory via GGA-WC, GGA-PBE and, TB-mBJ exchange-correlation potentials. The CrxCa1–xSe compounds are thermodynamically stable and synthesizable owing to their negative formation energies. The structural parameters of CrxCa1–xSe with GGA-WC and GGA-PBE approximations appear to be in excellent concordance compared to the experi-mental data and recent theoretical calculations. According to GGA-PBE and TB-mBJ calculations, the CrxCa1–xSe compounds revealed integral magnetic moments and a half-metallic behavior with better half-metallic gaps, and spin-polarization of 100%. The CrxCa1–xSe alloys appear to be better materials for use in spintronic devices.

First-principle simulation of inorganic Na2CuSbX6 (X = Cl, Br, I) halides for photovoltaic and energy conversion applications

The exceptional flexibility of optoelectronic attributes exhibited by inorganic Na2CuSbX6 (X = Cl, Br, I) halides has sparked significant interest in recent research. Our approach involves the utilization of Wien2k and BoltzTrap coding to scrutinize the mechanical, thermoelectric and optoelectronic attributes of studied halides. Structural stability have been investigated through Born stability criteria employing generalized gradient approximation (GGA-PBEsol). In addition, negative formation energy (−2.15 eV for Cl-halide, −1.88 eV for Br-halide and −1.68 eV for I-halide) indicate all halides are thermo-dynamical stable. For accurate calculation of optoelectronic properties, modified Becke and Johnson (mBJ) potential has been employed. Band structure indicate all halides are semiconductor with indirect bandgap nature having bandgap values 1.7 eV for Cl-halide, 1.34 eV for Br-halide and 0.85 eV for I-halide respectively. Substituting Cl-halide with Br and I-halide results in enhanced optical absorption predominantly in the visible region, causing a shift in the absorption edge from visible light to IR. Further, electronic thermoelectric properties are discussed against temperature 300 K to 800 K. The computed higher Seebeck coefficient observed in Na2CuSbI6 suggests that a narrower band gap is more suitable for thermoelectric applications in comparison to Na2CuSbBr6 and Na2CuSbCl6. In a broader context, the computational analysis of thermoelectric and optical properties indicates that Li2CuSbX6 halides is generally well suited for use in solar cell devices and energy conversion applications.

Investigation of structural, magnetic, mechanical, electronic and thermal properties of new quaternary Heusler: KMgNZ (Z=O or S)

The structural stability as well as the mechanical, magnetoelectronic and thermal properties of the quaternary Heusler KMgNZ (Z = O or S) were studied using first principles approach based on the DFT implemented in Wien2k code. The exchange-correlation potential is treated by PBE-GGA. The calculated negative formation energies for both materials corroborate their thermodynamic stability. Moreover, the derived elastic constants support the mechanical stabilities of the latter compounds. On the other hand, the density of states of the studied materials shows that both compounds are half-metallic ferromagnets. The total magnetic moments for both compounds are mainly originated from N atom, and its integer value followed the Slater-Pauling rule. The calculated half-metallic gaps are found for two systems. The three-dimensional plots of different mechanical moduli exhibit that the bulk modulus is isotropic, whereas Young's modulus, Poisson's ratio and shear modulus of both compounds are highly anisotropic. The effects of temperature and pressure on the heat capacity, thermal expansion coefficient and Debye temperature are also studied.

Comparative theoretical studies of BAs, AlAs, BBi and BSb compounds using density functional theory

A comprehensive investigation was conducted to analyze the physical properties, including electronic structure, optical characteristics, and thermoelectric properties, of four zinc blend structures: BAs, AlAs, BBi, and BSb. This analysis utilized first-principles calculations based on Density Functional Theory (DFT) and Boltzmann transport theories, implemented in the WIEN2K simulator program. The compounds examined displayed intriguing electronic and optical properties, such as low indirect band gaps of 0.726, 1.888, 0.867, and 1.51 eV for AlAs, BAs, BBi, and BSb, respectively. Moreover, these compounds exhibited high absorption in the UV–Visible region. Among the four compounds studied, BAs demonstrated exceptional structural stability due to its high bulk modulus and negative formation energy. The thermoelectric study revealed that the Seebeck coefficient decreased with increasing temperature, while the figure of merit was proportional to temperature enhancement. This behavior suggests that the investigated materials hold promise for applications in visible-light solar cell devices.

First principles study of chromium-based hydrides for optoelectronics and hydrogen storage applications

The first-principles study employed on chromium-based hydride XCrH3 (X: Na, K) is the first time studied and investigated different physical properties incorporated for optoelectronics and hydrogen storage applications. The structural properties results revealed that these materials have cubic phases, with lattice constants are 3.54 Å (NaCrH3), and 3.74 Å (KCrH3), which was also confirmed by the XRD analysis. The XRD results revealed that the intensity of KCrH3 is shifted towards to lower angle (2θ) degree due to high lattice constants and inter-planner distance. Moreover, both materials exhibited thermodynamically and mechanically stable due to negative formation energy, and elastic constants, and obeyed the Born approximation criteria. The phonons dispersion curve shows that XCrH3 is dynamically stable due to no imaginary frequency presence. Electronic properties found that current materials have metallic characteristics, due to zero band-gap energy, which plays a vital role in hydrogen storage applications. Magnetic properties exhibited paramagnetic behavior of current materials highly contributed to hydrogen storage application due to unpaired electrons and studied materials have spin-polarized magnetic nature. However, elastic properties confirmed that these materials are found hard, and brittle, with an ionic bonding nature between the atoms, and an anisotropic character. Besides this, different optical parameters have studied like as conductivity, absorption coefficient, refractive index, reflectance, and loss function and the results revealed that the examined materials dominated the role in LED, sensors, solar cells, and optoelectronics applications. Thermal analysis revealed that increasing temperature increases energy and entropy but decreases free energy. Among the studied materials, NaCrH3 has a high gravimetric ratio of 3.87 wt%, and KCrH3 is 3.21 wt%. These materials provided new potential for hydrogen storage applications.

Screening of Complex Layered Chalcogenide Structures as High-Performance Thermoelectrics by High-Throughput Calculations

Thermoelectric materials have drawn much attention over the last two decades due to the increase in global energy demand. However, designing efficient thermoelectrics reveals itself as a tough task for their properties (Seebeck coefficient, electrical conductivity, thermal conductivity) are mutually opposed. Hence, most recently, new design approaches have appeared, among which high-throughput methods have been implemented either experimentally or computationally. In this work, a high-throughput computer program has been designed to generate over 4000 structures based on a small set of complex layered chalcogenide compounds taken from the mAIVBVI nA2VB3VI homologous series, where AIV is Ge, AV is Sb and BVI is Te. The computer-generated structures have been investigated using density-functional theory methods, and the electronic and transport properties have been calculated. It has been found, using the quantum theory of atoms in molecules and crystals, that a wide variety of bond types constitutes the bonding network of the structures. All the structures are found to have negative formation energies. Among the obtained final structures, 43 are found with a wide band gap energy (>0.25 eV), 358 with semi-conductor/metal characteristics, and 731 with metallic characteristics. The transport properties calculations, using the Boltzmann equation, reveal that two p-type and 86 n-type structures are potentially promising compounds for thermoelectric applications.

First-principles study of the structural, mechanical, electronic, optical, and elastic properties of non-toxic XGeBr3 (X=K, Rb, and Cs) perovskite for optoelectronic and radiation sensing applications

In this study, a comprehensive analysis of the structural, electronic, optical, and elastic properties of cubic perovskite structure XGeBr3(X=K,Rb,andCs) was carried out using GGA-PBE functional based density functional theory in CASTEP code. The simulated values of the lattice parameter were increased with the changing of X from K to Cs (a = 5.51 Å, 5.54 Å, and 5.59 Å respectively). All the compounds possessed direct band gaps and acquired values for the structures KGeBr3, RbGeBr3 and CsGeBr3 were 0.525 eV, 0.599 eV, and 0.708 eV, respectively. Furthermore, the atomic orbital's contribution to the formation of band structure was clarified thoroughly. The thermodynamic, as well as the mechanical stability, has been accomplished with the assurance of negative formation energy and Born-Huang approximation. In addition, a larger shearing modulus attained by CsGeBr3 manifests its strength. Moreover, all structures bear the proof of having ductility and existing central force inside the structures. Finally, the calculated anisotropic index notifies that all structures exhibit anisotropy with the trend of CsGeBr3 < RbGeBr3 < KGeBr3. This is also authenticated through the 3D anisotropy contour plot generated by utilizing ELATE software, which is for the first time in regard to the comparative scenario among them. With the investigation of the optical characteristics of the compounds XGeBr3, intriguing features such as broad absorption spectrum, high dielectric function and refractive index at zero photon's energy, and high conductivity have been affirmed accompanying the marginal value of loss function as well as reflectivity that elevates the probability of being employed in optoelectronic applications along with different absorber layers of tandem solar cells. In addition, these compounds could be used as radiation detectors since they have broad absorption at extreme ultraviolet rays.

The physical attributes of rubidium-based Rb2TlRhF6 double perovskite halide: A first-principles investigation

Rubidium cations (Rb+) significantly improve the overall performance of organic-inorganic hybrid perovskite based devices and have gained exceptional attention due to their good thermal and structural stability. In this paper, we have evaluated the physical attributes of rubidium based Rb2TlRhF6 via DFT code using TB-mBJ potential. Structural stability has been confirmed through negative formation energy and calculated tolerance factor. Band structure and TDOS profile confirm semiconductor nature with 3.2 eV direct bandgap at (L-L) symmetry points. A ductile nature with metallic bonding is observed through the investigation of elastic attributes. Optical analysis of Rb2TlRhF6 indicates great absorption in the UV region. Low thermal conductivity and electrical resistivity, along with a high value for power factor, resulted in high ZT value of 0.8 and 800 K. The combined qualities provide a stunning and exciting picture of this compound for use in thermoelectric advanced technologies.

Physical properties of CoX'ZrGa (X' = V, Cr) quaternary-Heuslers: A first-principles investigation

The prime intention of this investigation is to examine the magnetic, thermoelectric, mechanical, electrical, structural, and thermodynamic characteristics of CoVZrGa and CoCrZrGa quaternary Heusler compounds. The FP-LAPW approach and Boltzmann transport equation are employed, utilizing classical Boltzmann approximations in the background of density functional theory (DFT) as implemented within WIEN2K software. The structure optimization employed the PBE approximations and the Murnaghan-Birch equation of state, leading to a stable phase for CoVZrGa and CoCrZrGa. The observed negative formation energy implies that the synthesis of CoVZrGa and CoCrZrGa is feasible. The Heusler compounds under investigation, which exhibit a narrow band gap in one spin direction and metallic behavior in the other, are classified as half-metallic (HM) based on the analysis of their electronic properties. The results for thermodynamic and elastic parameters confirm both alloys' thermal and mechanical stability. Critical analysis of thermoelectric properties demonstrates these compounds ssare feasible materials for thermoelectrical applications.

A Density Functional Theory Exploration of Cs2B′B″I6 (B′B″: BeCa, BeSr, GeCd, GeBe, GeMg) Halide Double Perovskites for Optimal Solar Cell and Renewable Energy Applications

A comprehensive investigation into the structural, elastic, optoelectronic, and thermoelectric properties of Cs2B′B″I6 halide double perovskites (DPs), where B′B″ represents various combinations, including BeCa, BeSr, GeCd, GeBe, and GeMg, is conducted. Using the full‐potential linearized augmented plane wave approach within the density functional theory framework, this analysis confirms the materials’ structural and dynamic stabilities through negative formation energies and adherence to elastic constant stability criteria. The generalized gradient approximation and the modified Becke–Johnson (mBJ) potential for electronic structure calculations are utilized. Notably, Cs2B′B″I6 DPs with B′B″ as BeCa or BeSr exhibit direct bandgaps (Γ–Γ), while those with B′B″ as GeCd, GeBe, or GeMg display indirect bandgaps (X–L). These findings offer valuable insights into the potential use of these materials in photovoltaic and optoelectronic devices. Furthermore, the exploration of thermoelectric properties, covering electrical conductivity, Seebeck coefficient, electronic thermal conductivity, and figure of merit at temperatures of 300, 600, and 900 K, suggests that Cs2B′B″I6 DPs, regardless of the specific B′B″ composition (BeCa, BeSr, GeCd, GeBe, GeMg), holds promise for applications in thermoelectric devices.

Comprehensive study of structural, elastic, electronic, optical, and thermoelectric properties of Rb2NaTlZ6 (Z = Cl, Br, and I) by DFT

The investigation focused on examining the structural, optical, elastic, and thermoelectric properties of the developing double perovskites Rb2NaTlZ6 (Z = Cl, Br, and I). The cubic phase of the investigated halide double perovskites (HDPs) was confirmed, based on the tolerance factor (τ) metrics of 0.853, 0.845, and 0.835, respectively. The thermodynamic stability of HDPs was evidenced by the negative formation energies. The mechanical stability, ductility, and anisotropic characteristics of the material under investigation are determined by its elastic parameters. The existence of a direct band gap (Eg) has been confirmed by density of states and electronic band gap calculations. The determined values for the band gap are 3.4, 2.6, and 2.1 eV, respectively. The current study centers on examining the absorption of light energy, refractive index, polarization, and optical loss across the complete energy spectra spanning between 0 and 10 eV. The spectral features revealed their appropriateness for photovoltaic energy systems due to the absorption unfolding within the UV spectrum. The thermoelectric properties, as assessed by using the BoltzTraP code, indicated that the highest ZT values obtained for both materials were 0.63, 0.63, and 0.71, respectively. Although these materials exhibit minimal optical absorption in the visible along with significant optical absorption in the ultraviolet region and possess a moderate ZT value, it is imperative to explore effective techniques for tuning the energy band gap to augment the thermoelectric and material's spectral properties. Therefore, this modification renders it more appropriate for experimental and practical utilization in the field of energy production.

Insights into the electronic, optical, and catalytic properties of finite biphenylene nanoribbons: First-principles study

The electronic, optical, and catalytic properties of finite two-dimensional biphenylene nanoribbons are investigated using density functional theory calculations. The nanoribbons are energetically and dynamically stable as confirmed by the negative formation energy ∼ -7 eV and the real vibrational frequencies, respectively. Increasing the length of nanoribbons in the zigzag or armchair directions reduces the energy gap, with modest oscillations in the former case. In contrast to zigzag graphene nanoribbons, biphenylene ones have nonmagnetic spin ordering due to the passivation of the unpaired electrons at the zigzag edges by the 4C- rings connecting the benzene rings. The UV–vis spectra exhibit redshifts, with size increases in both the armchair and zigzag directions, which validate the electronic computations' results. Simulating the catalytic performance of oxygen evolution reaction shows remarkable performance with a low overpotential of 0.12 V. Thus, biphenylene nanoribbons with desirable electronic and catalytic properties are attractive anode materials for water-splitting cells.

Intrinsic Room-Temperature Ferromagnetism in New Halide Perovskite AgCrX3 (X: F, Cl, Br, I) Using Ab Initio and Monte Carlo Simulations.

Herein, we present a detailed comparative study of the structural, elastic, electronic, and magnetic properties of a series of new halide perovskite AgCrX3 (X: F, Cl, Br, I) crystal structures using density functional theory, mean-field theory (MFT), and quantum Monte Carlo (MC) simulations. As demonstrated by the negative formation energy and Born-Huang stability criteria, the suggested perovskite compounds show potential stability in the cubic crystal structure. The materials are ductile because the Pugh's ratio is greater than 1.75, and the Cauchy pressure (C12-C44) is positive. The ground state magnetic moments of the compound were calculated as 3.70, 3.91, 3.92, and 3.91 μB for AgCrF3, AgCrCl3, AgCrBr3, and AgCrI3, respectively. The GGA + SOC computed spin-polarized electronic structures reveal ferromagnetism and confirm the metallic character in all of these compounds under consideration. These characteristics are robust under a ±3% strained lattice constant. Using relativistic pseudopotentials, the total energy is calculated, which yields that the single ion anisotropy is 0.004 meV and the z-axis is the hard-axis in the series of AgCrX3 (X: F, Cl, Br, and I) compounds. Further, to explore room-temperature intrinsic ferromagnetism, we considered ferromagnetic and antiferromagnetic interactions of the magnetic ions in the compounds by considering a supercell with 2 × 2 × 2 dimensions. The transition temperature is estimated by two models, namely, MFT and MC simulations. The calculated Curie temperatures using MC simulations are 518.35, 624.30, 517.94, and 497.28 K, with ±5% error for AgCrF3, AgCrCl3, AgCrBr3, and AgCrI3 compounds, respectively. Our results suggest that halide perovskite AgCrX3 compounds are promising materials for spintronic nanodevices at room temperature and provide new recommendations. For the first time, we report results for novel halide perovskite compounds based on Ag and Cr atoms.

DFT study of the half‐metallic variant perovskites A2OsX6 (A = Rb/Cs; X = Cl/Br) for spintronic and thermoelectric applications

AbstractWe present our results of the spin‐polarized calculations on the structural, magneto‐electronic, thermodynamic, and thermoelectric properties of vacancy‐ordered double perovskites A2OsX6 (A = Rb/Cs; X = Cl/Br). We utilized the Wu‐Cohen generalized gradient approximation (Wu‐GGA) and the mBJ scheme to determine a more reliable electronic structure. The compounds exhibit negative formation energy, suitable tolerance factor, and a stable phonon spectrum, indicating their stability. The compounds show half‐metallicity, acting as semiconductors with direct band gaps between 2 and 3 eV in the spin‐up orientation while metallic in the spin‐down. Each compound shows a total spin magnetic moment of 2.00 μB per formula unit, with Os‐t2g states contributing the most (~1.5 μB). The computed thermoelectric coefficient indicates the usability of these compounds across a wide temperature range (200–800 K) with high electrical conductivity and low electronic thermal conductivity. The compounds exhibit high Seebeck coefficient and figure of merit (ZT), making them suitable for thermoelectric applications. With ferromagnetic and half‐metallic characteristics, these compounds could be promising candidates for spintronics, thermoelectronic, and data storage applications.

Unveiling the mechanical, structural, thermoelectric, and optoelectronic potential of K2NaGaBr6 and K2RbTlBr6 double perovskites for sustainable technologies

Double perovskite halide's remarkable physical qualities and ease of synthesis have drawn much interest in the past few years. To analyze the structural and thermodynamic stability, elastic traits, optical, and thermoelectric analysis of the double perovskites K2NaGaBr6 and K2RbTlBr6, FP-LAPW technique is employed in current work. Exchange correlation effects are treated with PBE-GGA and TB-mBJ approximations. Thermodynamic stability of structures is ensured with computed phonon curves and negative formation energies. Goldsmith tolerance factor and octahedral tilting justify the cubic phase of both perovskites. Mechanical attributes justify Born’s stability criteria and double perovskites' anisotropic and ductile nature. The semiconducting nature is confirmed by electronic band structures with direct bandgap of 1.43 eV and 3 eV for K2NaGaBr6 and 1.48 eV and 2.51 eV for K2TlRbBr6 with PBE-GGA and TB-mBJ, respectively. Optical properties for K2NaGaBr6 and K2RbTlBr6 reveal significant absorption of electromagnetic waves in visible and UV regions. Furthermore, thermoelectric response for both double perovskites is computed using BoltzTraP code, which reveals their significant abilities for usage in thermoelectricity and renewable energy applications.

Computational study of stability, photovoltaic, and thermoelectric properties of new inorganic lead-free halide perovskites

Abstract Due to their rich and extraordinary properties, halide perovskites have gained attention over time for their applications in thermoelectric and solar cells. Here, several physical properties (stability, photovoltaic, and thermoelectric) of inorganic halide perovskites XZnI3 (X = Na, K, Rb, Cs) are predicted using the density functional theory (DFT) within the Wien2k code. The optimization of structural parameters has been calculated using PBE-GGA approach. The tolerance factor, Born criteria, phonon dispersion, and negative formation energy show the formation and stability of these studied materials in the ideal cubic structure. Additionally, the modified Becke-Johnson method is applied for optoelectronic and transport properties. All compounds exhibit the nature of indirect band gap semiconductors with better absorption in the visible and ultraviolet regions 10^{5} \textrm {cm}^{-1})$ ?> . The transport properties present high electrical conductivity, large Seebeck coefficient, and good (PF, ZT) factors for all these materials. Finally, all these properties of inorganic halide perovskites open up new possibilities for efficient applications in thermoelectric and solar cells.

The first principles insights of aluminum-based hydrides for hydrogen storage application

Hydrogen storage is an urgent issue for mobile applications, to overcome this issue solid materials have a potential role for hydrogen storage applications. Moreover, the perovskite hydride materials have been extensively investigated for improvement in the field of hydrogen storage. However, this work is focused on the computational study of XAlH3 (X: Na, Mg) perovskite-type hydrides for different physical properties and hydrogen storage applications. Both materials were found thermodynamically, and mechanically stable from the negative formation energy and elastic properties. They exhibited cubic phases with computed lattice constants are 3.827 Å and 3.752 Å, respectively. The electronic properties indicated that both compounds have a metallic nature, and found the high contribution of Al-p state, and H-1s state near the Fermi level. However, the Hirshfeld net charge analysis detected, that charge transfer from Al and X (Na, Mg) atoms to H atoms. Furthermore, the metallic hydrides have promised candidates for hydrogen storage applications. Both compounds have observed non-magnetic behavior with zero magnetic moments. Elastic constants were calculated to determine the mechanical stability of the compounds, it was found that MgAlH3 is harder than NaAlH3, and it exhibited that higher Bulk, Shear, and Young's modulus. The Poisson's, and Pugh's (G/B) ratios suggested that ionic boning of the atoms, additionally, Pugh's ratio (B/G) and Cauchy pressure (Cp) confirmed that NaAlH3 ductile and MgAlH3 is brittle behavior. Besides this, Optical properties were determined for both compounds including the dielectric function, conductivity, refractive index, absorption, and loss function. It is found that the MgAlH3 compound optical more suitable than NaAlH3 due to calculated optical factors promised and both compounds are undertaken for solar cells, optoelectronics, and energy storage applications. Finally, the computed hydrogen storage capacity for NaAlH3 and MgAlH3 compounds are 6.01 wt%, and 5.56 wt% respectively. These results revealed that both have the potential materials for hydrogen storage, but NaAlH3 unique material to fulfill the US-DOE criteria of 2020.

A DFT insight into the physical features of alkaline based perovskite compounds AInBr3 (A = K, Rb)

Owing to their proper characteristic, simple halide perovskites became engaged over time for thermoelectric applications. In this work, several physical properties of simple halide perovskite materials AInBr3 (A = K, Rb) are predicted based on density functional theory (DFT) within the Wien2k code. The tolerance factor and negative formation energy demonstrate the stability and formation of these compounds, and the Born criteria shows their mechanical stability and inherent ductility. Notably, the modified Becke-Johnson potential (mBJ) was used to calculate the optoelectronic characteristics. The AInBr3 (A = K, Rb) perovskites present semiconducting aspects. Analyses of their optical characteristics, including refractive index, reflectivity, were performed. AInBr3 (A = K, Rb) transport properties were studied. The highest figure of merit was attained by AInBr3 (A = K, Rb) which had a high Seebeck coefficient and high electrical conductivity. Finally, all studied properties of simple halide perovskites give a new way for efficient applications in thermoelectric.

DFT-based first-principles calculations of new NaXH[formula omitted] (X = Ti, Cu) hydride compounds for hydrogen storage applications

Density functional theory (DFT) was employed to perform an ab-initio study of new hydrogen storage materials NaXH3 (X = Ti, Cu) using the Generalized Gradient Approximation (GGA) and CASTEP package. The structural, electronic, elastic, optical, and hydrogen storage properties of NaTiH3 and NaCuH3 were calculated within the Pm3̄m cubic-perovskite phase. The thermodynamic stability of both structures was ensured by their negative formation energy. The dynamic stability has been investigated through phonon dispersion, and it has been proven that these compounds are stable. The calculations of elastic constants confirm the mechanical stability of these materials. Furthermore, bulk modulus, shear modulus, and Poisson’s ratio have been derived by employing the obtained elastic constants. NaXH3 hydrides were found to be elastically anisotropic and brittle. The electronic band structures turn out metallic behavior in NaXH3 perovskites. The optical characteristics demonstrate that both compounds exhibit their highest absorption and conductivity levels within the ultraviolet wavelength range. The calculation of gravimetric hydrogen storage capacities for NaTiH3 and NaCuH3 was performed and found to be ≈3.932 and 3.266 wt%, respectively. The hydrogen desorption temperature was identified as 637 and 563 K for NaTiH3 and NaCuH3, respectively. The current DFT results highlight that NaXH3 (X = Ti, Cu) hydrides have considerable potential as candidates for H2 storage purposes.

Investigation of work function and quantum capacitance of OH-terminated MXenes as supercapacitor electrodes: A theoretical perspective

MXene has shown promise in supercapacitor electrodes for energy storage devices. As key parameters to develop new electronic devices, the quantum capacitance and work function (WF) of OH-terminated MXenes with 3d, 4d, d transitional metals are investigated by density functional theory. The most stable configurations of 13 M2C(OH)2 MXenes are found, which are further confirmed by negative formation energies. The low WFs of M2C(OH)2 make them become potential candidates as thermionic electron emitters, especially for Sc2C(OH)2 and Lu2C(OH)2 with extra low WFs. Sc2C(OH)2, Cr2C(OH)2, Y2C(OH)2, and Lu2C(OH)2 are considered as negative electrodes, Other nine systems are potential positive electrodes for larger |Qp|/|Qn| than 1, especially for V2C(OH)2, Nb2C(OH)2, and Mo2C(OH)2. Th wide voltage maintains the electrode types of all systems unchanged, but drastically increases the |Qp|/|Qn| of V2C(OH)2. The quantum capacitance of M2CT2 with different terminations is further explored.