First-principles Investigation of Structural, Electronic, Mechanical, Optical, and Thermodynamic Properties of Lead-Free KSrX3 (X = F, Cl, and Br) Halide Perovskites for UV Optoelectronic Applications
This study employed density functional theory (DFT) within Quantum ESPRESSO to
investigate the structural, electronic, phonon, mechanical, optical, and thermodynamic
properties of cubic KSrX₃ (X = F, Cl, Br) halide perovskites for UV optoelectronic applications.
All compounds were found to be structurally, thermodynamically, mechanically, and
dynamically stable, as confirmed by negative formation energies, appropriate Goldschmidt
tolerance factors, Born stability criteria, and phonon spectra without imaginary frequencies.
KSrF₃ exhibited a direct band gap of 5.52 eV, while KSrCl₃ and KSrBr₃ showed indirect band
gaps of 4.45 and 3.75 eV, respectively, making KSrF₃ the most promising candidate for deepUV applications. The compounds exhibited ductile behavior, characterized by dominant ionic
bonding, low Debye temperatures indicative of low lattice thermal conductivity, and
thermodynamic properties consistent with the third law of thermodynamics and Dulong–Petit’s
law. Optical calculations revealed strong UV absorption and static dielectric constants of 2.02,
2.46, and 2.56 for KSrF₃, KSrCl₃, and KSrBr₃, respectively, highlighting their potential for UV
optoelectronic devices.
In contrast to traditional lead-based perovskites, double perovskites are receiving considerable attention owing to their highly tunable photovoltaic performance and remarkable stability, which can be further enhanced through compositional engineering. We have theoretically investigated the structural, mechanical, dynamical, optical, and electronic properties of Cs2RbCoX6 (X = F, Cl, Br, and I) using first-principles calculations performed with VASP. The structural and mechanical stability of the investigated cubic structures was assessed using tolerance factors, formation energies, and elastic constants. Phonon dispersion calculations further demonstrate dynamical stability for Cs2RbCoF6, Cs2RbCoCl6, and Cs2RbCoBr6, whereas Cs2RbCoI6 exhibits imaginary phonon modes, indicating a dynamical instability of the ideal cubic phase. The bulk, shear, and Young’s moduli, Debye temperature, melting temperature, and average acoustic sound velocity exhibit systematic trends across the halide series. Electronic structure calculations reveal semiconducting behavior, with GGA-PBE predicting direct X-point band gaps for Cs2RbCoF6, Cs2RbCoCl6, and Cs2RbCoBr6, whereas Cs2RbCoI6 exhibits an indirect Γ→X gap. HSE06 substantially increases the calculated band gaps and predicts an indirect Γ→X character for all four compounds, highlighting the sensitivity of the band-edge topology to the exchange-correlation treatment. The optical properties, evaluated at the GGA-PBE level, show enhanced low-energy absorption for the Cs2RbCoCl6, Cs2RbCoBr6, and Cs2RbCoI6, while Cs2RbCoF6 is predominantly active in the ultraviolet region. These findings underscore the potential of Cs2RbCoX6 as promising lead-free double-perovskite candidates for diverse optoelectronic and photonic technologies, depending on their specific electronic and optical responses.
The structural, mechanical, and optoelectronic properties of cubic halide perovskites KZnX3 (X = Cl, Br) were investigated using density functional theory (DFT) within the full-potential linearized augmented plane wave (FP-LAPW) method, as implemented in the WIEN2k software. The optoelectronic properties were further examined using the Tran–Blaha modified Becke–Johnson (TB-mBJ) potential. The results indicate that both compounds are structurally stable within the generalized gradient approximation of the Perdew–Burke–Ernzerhof (PBE-GGA). KZnCl3 exhibits insulating behavior with an indirect band gap of 4.06 eV, whereas KZnBr3 exhibits semiconducting characteristics with an indirect band gap of 2.23 eV. The calculated elastic constants and formation energies confirmed that both compounds were mechanically and thermodynamically stable. Furthermore, the optical properties were analyzed in the photon energy range of 0–30 eV. Both compounds exhibit strong absorption in the ultraviolet region, indicating their potential for optoelectronic applications, particularly in ultraviolet (UV) devices.
H. Bouheraoua, E. Belbacha· Physics of the Solid State· 0 citations
In this study, a new semiconducting material, InPSi
3
, has been explored using density functional theory (DFT) calculations, along with an investigation of the unexplored properties of the newly predicted AlPSi
3
and GaPSi
3
semiconductors. The negative formation energy, elastic constants, and positive phonon modes certify the stability of all three compounds. InPSi
3
is an indirect‐band‐gap semiconductor (1.58 eV), whereas AlPSi
3
and GaPSi
3
are direct band gaps with an
E
g
of 1.64 and 1.51 eV, respectively. We used DOS to investigate the nature of bonding. Additionally, optical coefficients, including the dielectric constant, refractive index, extinction coefficient, photoconductivity, optical absorption, reflectivity, and loss function, were computed. The mechanical behavior was studied by calculating elastic constants, elastic moduli, and brittleness indices. The thermal parameters, including Debye temperature, melting temperature, thermal conductivity, minimum thermal conductivity, thermal expansion coefficient, and specific heat capacity, have been investigated. The thermoelectric properties, including electrical conductivity (
σ
/
τ
), electronic thermal conductivity (
K
e
/
τ
), Seebeck coefficient (S), power factor (PF), and figure of merit (ZT), were calculated. The titled materials would be appropriate for individual solar cells or the top portion of tandem solar cells, owing to their appropriate band gap and optical absorption.
S. Datta, S. Mahmud, M. M. Hossain et al.· Advanced Physics Research· 0 citations
The current study systematically investigates the optoelectronic, mechanical, transport, and thermodynamic properties of Pb-free halide-based double perovskites (Rb
2
LiIrX
6
, where X = Cl, Br) for energy conversion. Using density functional theory (DFT) within the fullpotential linearized augmented planewave (FPLAPW) framework implemented in the Wien2k code, structural optimizations were performed through the PBEsol generalized gradient approximation (GGA). Energy calculations yield values of −0.63 eV (Cl) and −0.41 eV (Br) for the cubic phase, confirming thermodynamic stability. Electronic band structures obtained with the modified BeckeJohnson (mBJ) potential reveal direct bandgaps of 2.25 eV (Cl) and 1.69 eV (Br); these findings are further validated by HSE06 hybrid functional calculations, establishing the semiconducting nature of both compositions. Mechanical robustness is confirmed through elastic constants and phonon dispersion analyses, demonstrating resilience against structural deformations. Optical properties display high absorption coefficients, elevated static dielectric constants, low reflectivity, and pronounced photoconductivity, highlighting the material's promise for photovoltaic and photodetector applications. Moreover, low lattice thermal conductivity and thermoelectric figureofmerit (ZT) values approaching unity suggest additional potential for thermoelectric energy harvesting. The high Debye temperatures and negative Gibbs free energies over a wide temperature range indicate the thermal stability of these compounds under operational circumstances.
Muhammad Ahsan, M. Ammar Yasir, M. Bououdina et al.· Modern physics letters B· 0 citations
This work presents a first-principles study of the structural, mechanical, dynamical, electronic, and thermoelectric properties of the ternary Heusler compounds Ir
2
YSi (Y = Be, Ca, Sr). These materials crystallize in the cubic L2
1
structure (space group [Formula: see text]) and are found to be thermodynamically stable, with the non-magnetic state being energetically favored.
The calculated elastic constants satisfy the Born criteria, confirming mechanical stability for all compounds, although Ir
2
SrSi shows relatively lower rigidity. Phonon dispersion curves exhibit no imaginary frequencies, indicating dynamical stability, with vibrational properties influenced by atomic mass differences.
Electronic structure analysis reveals a metallic character for all compounds, with dominant Ir-[Formula: see text] states near the Fermi level and notable hybridization with Si-[Formula: see text] orbitals. A pseudo-gap observed in Ir
2
CaSi and Ir
2
SrSi suggests enhanced stability compared to Ir
2
BeSi.
Thermoelectric properties show metallic behavior with increasing electrical and thermal conductivities as temperature rises. Despite some improvement across the series, the maximum figure of merit remains low ([Formula: see text]), limiting their efficiency for thermoelectric applications.
In this study, we conduct a detailed first-principles investigation of the structural, electronic, optical properties, thermodynamic and mechanical stability of K
$$_3$$
GaX
$$_6$$
(where X = Cl, Br, I) for optoelectronic applications. This investigation is carried out using density functional theory (DFT) within the Quantum ESPRESSO framework, applying the generalized gradient approximation with the Perdew–Burke–Ernzerhof functional. The structural properties were studied by full geometry optimization and the stable lattice parameters were obtained for all the compounds. The charge density distribution shows a strong ionic character and is significantly localized around halide ions, which confirms the bonding nature within the [GaX
$$_6$$
] octahedral units. The calculated negative formation energies and elastic constants satisfying the Born criteria indicate that the investigated compounds are thermodynamically favorable and mechanically stable. For the electronic properties, the band gap of K
$$_3$$
GaCl
$$_6$$
, K
$$_3$$
GaBr
$$_6$$
and K
$$_3$$
GaI
$$_6$$
were calculated. A similar decreasing trend is observed in the optical properties such as absorption coefficient, optical conductivity and plasmonic response from Cl to Br to I. In contrast, the reflectivity is almost invariant over the series, suggesting similar surface interaction behavior despite the compositional variation. The projected density of states reveals that the valence band maximum is predominantly derived from the halogen p orbitals, while the conduction band minimum is mainly composed of Ga s and Ga p orbitals. The Ga-3d states are located at lower energies and do not contribute significantly to the electronic states near the Fermi level. Among the compounds studied, the calculated band-gap values show that the K
$$_3$$
GaX
$$_6$$
(X = Cl, Br and I) compounds are promising for optoelectronic applications in different spectral regions. K
$$_3$$
GaI
$$_6$$
with a narrow direct band gap of 0.80 eV is promising for near-infrared (NIR) applications, such as infrared photodetectors and NIR optoelectronic devices. K
$$_3$$
GaBr
$$_6$$
has an intermediate direct band gap of 2.05 eV, which is in the visible spectral range, and thus, it is a promising candidate for visible-light optoelectronic devices, such as photodetectors, light-emitting devices and optical sensors. On the other hand, K
$$_3$$
GaCl
$$_6$$
has a large direct band gap of 3.32 eV, suggesting that it can be a good candidate for ultraviolet (UV) and near-UV optoelectronic applications such as UV photodetectors, optical coatings and ultraviolet filtering devices.
Tamene Dechasa Beri, M. Alemu, D. Hirpa et al.· Materials for Renewable and...· 0 citations
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