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The current investigation employs first‐principles DFT (density functional theory) calculations to examine the influence of transition metal replacements on the structural, thermodynamic, and thermoelectric properties of Cu‐based chalcogenides TMCu3Se4 (TM = Nb/Ta/V). The PBE‐generalized gradient approximation (GGA) model is utilized to compute the fundamental properties of Cu‐based chalcogenides under study. A thorough examination of the energy band structures indicates that these chalcogenides are semiconductor compounds with indirect energy bandgaps. We can infer from the calculated energy band structures that the bandgap values are 1.67, 1.77, and 1.05 eV for NbCu3Se4, TaCu3Se4, and VCu3Se4, respectively. The ZTe$$ {\mathrm{ZT}}_e $$ values for NbCu3Se4, TaCu3Se4, and VCu3Se4 are 0.661, 0.998, and 0.996, respectively. These values make them highly appropriate for usage in thermoelectric (TE) devices. The thermoelectric characteristics of pyrochlore oxides TMCu3Se4 (TM = Nb/Ta/V) suggest that these materials have promising potential for energy‐related applications. The analyzed thermodynamic properties demonstrate that the Cu0based chalcogenide materials TMCu3Se4 (TM = Nb/Ta/V) exhibit a notable level of thermal stability. [ABSTRACT FROM AUTHOR]

In order to address the energy challenges of the near future, researchers are currently focused on developing environmentally friendly and energy-efficient phosphors for luminescence devices such as light-emitting diodes (LEDs). When it comes to this topic, older lighting devices such as halogen lamps, LCD backlights, incandescent lamps, and fluorescent lamps can be substituted with advanced next-generation lighting technology created with phosphor-transformed white LEDs. We've conducted a detailed analysis of the structural and optoelectronic characteristics of Cs-based phosphors Cs2MF6 (M = C, Ge, Pb, Si) for potential use in photoluminescence as well as photovoltaic applications such as LEDs. Utilizing the GGA scheme allows for an in-depth analysis of exchange and correlation energy potentials within density functional theory (DFT) first-principles calculations. The calculated structural properties reveals that Cs2PbF6 is the most stable compound among Cs2MF6 (M = C, Ge, Pb, Si) as they possess lowest ground state energy. Direct bandgaps of 1.57, 1.459, 1.481, and 1.59 eV are observed with the presence of intermediate bands for Cs2CF6, Cs2GeF6, Cs2PbF6, and Cs2SiF6, respectively. It is established by analyzing plots that the investigated hexafluorides absorb maximum photons in the UV region. Based on the spectra, it is evident that Cs2MF6 (M = C, Ge, Pb, Si) act as weak reflectors of incident photons in the visible and IR regions. However, around 40% of the incoming photons get reflected at various energies by individual compounds. Thermodynamic characteristics of these hexafluorides reveals that they are thermodynamically stable compounds. [ABSTRACT FROM AUTHOR]

• Optoelectronic and thermodynamic, properties of ATiO 3 (A = Ba, Ca, Ra) are investigated using first-principles method. • ATiO 3 (A = Ba, Ca, Ra) shows efficient photon absorption in near UV regions. • ATiO 3 (A = Ba, Ca, Ra) show high thermodynamic stability and is a promising candidate for device applications. • These compounds are optically active compounds as their refractive index occurs between 1.0 and 2.0. The structural, optoelectronic, and thermodynamic characteristics of ATiO 3 (A = Ba, Ca, Ra) perovskites have comprehensively been investigation first-principles based DFT calculations. The GGA method was employed to handle exchange and correlation potentials. The analysis of the E-V plots indicates that RaTiO 3 exhibits the highest level of stability in comparison to BaTiO 3 and CaTiO 3. The direct band-gap characteristic of the ATiO 3 (A = Ba, Ca, Ra) perovskites is apparent in the band structure plots. The band gaps for BaTiO 3 , CaTiO 3 , and RaTiO 3 are 2.48, 3.15, and 1.91 eV, respectively. The analyzed materials exhibit the highest level of photon absorption in the near UV area, as demonstrated in the ε 2 (ω) plots. The refractive index n (ω) values reveal that ATiO 3 (A = Ba, Ca, Ra) are active optical materials as their n (ω) values are between 1 and 2. These perovskite oxides have optical features that make them promising prospects for anti-reflecting coatings over entire energy span as these materials exhibits a very low reflection (∼20 %) of incident photons. The thermodynamic properties of ATiO 3 (A = Ba, Ca, Ra) are assessed to determine their dynamical stability and suitability for thermal applications. The results of the investigation demonstrate that these perovskite oxides have the potential to be used in optoelectronic devices. [ABSTRACT FROM AUTHOR]

[Display omitted] • New energy harvesting mechanisms as alternatives for traditional energy sources. • Optoelectronics and thermoelectricity have gained much attention. • High absorption capability of the incident photons. • The future of thermoelectric generators. • High figure of merit promising for thermoelectric applications. We have investigated the optoelectronic and thermophysical properties of ABi 4 Ti 4 O 15 (A = Ba, Ca) using first principles DFT computations. The FP-LAPW technique employed in the WIEN2K code allows for accurate estimation of the ground state parameters of crystalline materials. The phonon spectra, formation energies, and other thermodynamic aspects of these layered perovskite materials indicate that they are thermodynamically stable. The analysis of energy band structures indicates that BaBi 4 Ti 4 O 15 and CaBi 4 Ti 4 O 15 are indirect semiconductors with energy band gaps of 1.89 eV and 1.76 eV, respectively.CaBi 4 Ti 4 O 15 has greater structural stability in comparison to BaBi 4 Ti 4 O 15.The analysis of optical characteristics reveals that these compounds exhibit high photon absorption in UV region. The static refractive index n ω values for BaBi 4 Ti 4 O 15 and CaBi 4 Ti 4 O 15 are 1.91 and 1.89, respectively. These values show optical activeness of these compounds since their n (ω) values fall within the range of 1.0 to 2.0. The figure of merit (ZT) values of 1.43 and 1.36 for BaBi 4 Ti 4 O 15 and CaBi 4 Ti 4 O 15 , respectively, make them highly suitable for thermoelectric device applications. [ABSTRACT FROM AUTHOR]

• Both RbInH 3 and CsInH 3 exhibit favorable thermodynamic stability with negative formation enthalpies of −4.29 eV/atom and −6.41 eV/atom, respectively. • The lattice parameters are 4.35 Å for RbInH 3 and 4.44 Å for CsInH 3 , confirming their crystallographic stability and structural consistency. • Both RbInH 3 and CsInH 3 show hydrogen storage capacities of 1.45 % and 1.18 %, respectively. • Both materials exhibit metallic behavior, which could enhance conductivity but may limit hydrogen storage efficiency. Efficient hydrogen storage materials are essential for the advancement of sustainable energy solutions. This work employs density functional theory (DFT) to examine the capacity of XInH 3 (X = Rb and Cs) as materials for storing hydrogen in solid-state. The crystal structures of RbInH 3 and CsInH 3 , which both belong to the space group pm3m, with lattice parameters of 4.35 Å and 4.44 Å, respectively. The formation enthalpies of RbInH 3 and CsInH 3 are −4.29 eV/atom and −6.41 eV/atom, respectively, suggesting that they possess favorable thermodynamic stability. The gravimetric hydrogen storage capacities of RbInH 3 and CsInH 3 are 1.45 % and 1.18 % respectively. An examination of the electronic structure indicates the presence of metallic properties, characterized by the overlapping of the valence and conduction bands. The optical characteristics of RbInH 3 and CsInH 3 demonstrate substantial absorption in the ultraviolet (UV) region, with RbInH 3 having a peak at 20.25 electron volts (eV) and CsInH 3 at 16.92 eV. The mechanical properties demonstrate anisotropic behavior and imply brittle features. The evaluation also includes thermodynamic properties such as the Debye temperature and melting temperatures. These findings suggest that RbInH 3 and CsInH 3 , with their favorable structural stability and ease of synthesis, could be integrated into current hydrogen storage technologies, offering a pathway for further optimization to enhance their practical applicability. [ABSTRACT FROM AUTHOR]

A systematic study has been performed on structural, optical and thermophysical properties of newly designed pyrochlore oxides Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) employing FP-LAPW based first-principles calculations. The GGA approach was used to treat exchange and correlation potentials. The investigated E-V plots reveals that Sr 2 Sb 2 O 7 is the most stable structure compared to Be 2 Sb 2 O 7 /Ca 2 Sb 2 O 7. A direct energy bandgap of 0.29 eV is evident from band structure plot of Be 2 Sb 2 O 7 , however, Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 possess indirect energy bandgaps of magnitude 1.47/1.467 eV. The studied materials show maximum absorption of incoming photons in near UV region as shown in ε 2 (ω) plots, however, considerable absorption in visible region is also present. Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are effective optical material with a n (ω) value between 1.0 and 2.0. Optical properties of pyrochlore oxides reveal that these materials are potential candidates for shielding materials in upper UV region. A photon reflection of up to 60% is evident from the R (ω) in UV region, however, in IR and visible regions, the reflectance is negligible. Based on calculated values of Seebeck coefficient (S), we can state that Be 2 Sb 2 O 7 is n-type semiconductor whereas Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are p-type semiconductors. The most effective thermoelectric material among Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) is Ca 2 Sb 2 O 7 as its ZT value is highest (∼1.05) in the entire temperature range. Thermodynamic properties of Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are also evaluated to check dynamical stability and appropriateness of these materials in thermal applications. The investigated outcomes show that these pyrochlore oxides are potential candidates for thermoelectric and optoelectronic device applications. • Ground state properties of pyrochlore oxides Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are investigated using ab-initio. • Q 2 Sb 2 O 7 (Q = Be, Ca, Sr) are narrow band semiconductors. • Be 2 Sb 2 O 7 is n-type semiconductor, however, Ca 2 Sb 2 O 7 /Sr 2 Sb 2 O 7 are p-type semiconductors. • Optical spectra show major absorption peaks for these pyrochlore oxides occur in visible region. [ABSTRACT FROM AUTHOR]