arXiv subjects

S. S. B. Pallab

Publications and source records attributed to S. S. B. Pallab.

3 recordsLinked to original sources

arXiv2026

Multifunctionality in Janus CrMCN4 (M = Si/Ge) Monolayers: Valleytronic Physics, Piezoelectric Response, and Photocatalytic Potential

Two dimensional Janus semiconductors integrating spin-valley coupling, piezoelectricity, and tunable optical responses offer a platform for multifunctional nanodevices. Here, first-principles calculations reveal complementary composition and strain effects in CrSiCN4 and CrGeCN4 monolayers. Both are found to be nonmagnetic direct-gap semiconductors, with gaps of 1.23 and 1.09 eV using the Perdew-Burke-Ernzerhof functional including spin-orbit coupling, respectively. HSE06 hybrid-functional calculations retain the direct-gap character, yielding gaps of 1.46 eV for CrSiCN4 and 1.19 eV for CrGeCN4. Opposite out-of-plane spin character and Berry curvature emerge at K and K'. Biaxial strain reduces the respective gaps from 1.59 to 0.86 eV and 1.44 to 0.63 eV, drives direct-to-indirect transitions, and redshifts absorption while preserving valley spin contrast. CrGeCN4 exhibits larger in-plane piezoelectric response, whereas CrSiCN4 exhibits larger out-of-plane magnitude. Band-edge alignment satisfies the oxygen evolution reaction requirement but provides insufficient driving force for the hydrogen evolution reaction, motivating further strain-induced band-edge modulation toward overall water splitting. These results establish composition and strain as complementary controls for tailoring Cr-based Janus monolayers for valleytronic, optoelectronic, electromechanical, and photocatalytic applications.

cond-mat.mtrl-sci↗

arXiv2026

Phase Switchable Photocatalytic Water Splitting via a Paraelectric-Ferroelectric Transition in Zr2Ge2S6 Monolayer: A Comprehensive Theoretical Insights

Photocatalytic water splitting (PWS) is a promising technology for addressing the global energy crisis and producing renewable and clean hydrogen fuel. Although numerous 2D materials have recently been proposed as potential photocatalysts, effective strategies for regulating photocatalytic reactions and improving energy conversion efficiency remain limited due to performance regulation challenges. Here, using first-principles calculations, we demonstrate that the photocatalytic activity and energy conversion efficiency of a Zr2Ge2S6 monolayer can be effectively tuned through a paraelectric-ferroelectric phase transition. The Zr2Ge2S6 monolayer exhibits excellent structural stability, favorable mechanical properties, a suitable band gap, optimal band edge positions, and broad-spectrum light absorption. Moreover, the Zr2Ge2S6 monolayer exhibits a higher oxidation potential and a stronger driving force for photogenerated holes to promote oxygen evolution reaction (OER) in the ferroelectric phase. In contrast, the paraelectric phase provides photogenerated electrons with a greater reduction potential and driving force for hydrogen evolution reaction (HER). The solar-to-hydrogen conversion efficiency is also strongly influenced by the phase transition, increasing from 7.71% in the paraelectric phase to 15.31% in the ferroelectric phase because of the improved carrier utilization. Our theoretical investigation not only highlights the crucial role of ferroelectric polarization in photocatalytic water splitting but also provides an effective strategy for tuning the photocatalytic properties of 2D ferroelectric materials through ferroelectric switching.

cond-mat.mtrl-sci↗

arXiv2026

First-Principles Study of Novel Lead-Free Double Perovskite \b{eta}2SnGeX6 (\b{eta} = K, Rb; X = Cl, Br, I) for thermomechanical, optoelectronic and outstanding thermoelectric applications

In this study, the structural, mechanical, electronic, optical, and thermoelectric properties of the novel lead-free halide double perovskite series beta2SnGeX6 (beta = K, Rb; X = Cl, Br, I) are systematically investigated using density functional theory (DFT). Calculated formation energies, Tolerance factors, and octahedral factors confirm that all six compounds exhibit robust thermodynamic stability within a highly symmetric cubic geometry. Mechanical analysis derived from elastic parameters characterizes the entire series as fundamentally ductile, ensuring high processing elasticity and resistance to micro-cracking during device manufacturing. Electronic band structures reveal direct bandgaps showing exceptional composition-dependent tunability from 1.44 eV down to 0.64 eV via progressive halogen substitution. The wide gap chloride variations are optimized for single-junction photovoltaic absorbers, while the narrower-gap bromide and iodide analogs show immense promise for tandem solar architectures and near-infrared photodetectors. Thermoelectrically, heavy constituent atoms introduce strong lattice anharmonicity and intense high-temperature Umklapp phonon scattering, significantly suppressing lattice thermal conductivity. Combined with low carrier effective masses that optimize electrical transport, the iodide compounds achieve higher power factors and outstanding dimensionless figures of merit (ZT = 2.4 for K2SnGeI6 at 1000 K). Ultimately, these lead-free double perovskite family emerges as an environmentally benign and versatile platform for next-generation green optoelectronics and solid-state waste-heat recovery.

cond-mat.mtrl-sci↗