The machine learning (ML) based approaches efficiently solve the goal of searching the best materials candidate for the targeted properties. The search for topological materials (TMs) using traditional first-principles and symmetry-based methods often require lots of computing power or is limited by the crystalline symmetries. In this study, we present frequency-based statistical descriptors for ML-driven TM's classification that is independent of crystallographic symmetry of wave functions. This approach predicts the topological nature of a material based on its chemical formula. With a balanced dataset of 3880 materials, we have achieved classification accuracies of 82% with the support vector machine model and 83% with the random forest model, where both models have trained on common frequency based features. We have verified the performances of the models using 5-fold cross-validation approach. Moreover, we have validated the models on a dataset of unseen binary compounds and have efficiently identified 22 common materials using both the models. Next, we used the first-principles approach to provide preliminary evidence for the topological candidates via band inversions at time-reversal invariant momenta points. Therefore, we have demonstrated that the implications of frequency-based descriptors is a practical and less complex way to find novel TMs with certain physical post-processing filters. This approach lays the groundwork for scalable, data-driven topological property screening of complex materials.

In this work, density functional theory-based simulation is used for investigating the structural and electronic properties of Janus monolayers CrSSe and CrSeTe. Electronic bandgap values of 0.85 eV and 0.62 eV are obtained for CrSSe and CrSeTe, respectively. Further, the semiclassical Boltzmann theory is used for assessing the thermoelectric parameters including the Seebeck coefficient, electrical and thermal conductivity, and thermoelectric performance (ZT) of the monolayers. The values of Seebeck coefficient and lattice thermal conductivity for (n-type) p-type Janus monolayers CrSSe and CrSeTe are (1340) 1390 µV K−1, (971) 1010 µV K−1, and (11.01) 0.25 W/K, respectively. The ZT values for (n-type) p-type Janus monolayers CrSSe and CrSeTe are (0.92) 0.93 and (0.95) 0.96, respectively, at room temperature. The thermoelectric performance of these monolayers is higher than for the homogeneous CrSe2 monolayer due to their unique structural and compositional characteristics. These results contribute valuable insights for the design and optimization of Janus monolayers for advanced thermoelectric applications, and pave the way for promising advancements in sustainable energy harvesting.

We have investigated the structural, dynamical, and topological phase in the ternary chalcogenide material SnPbSe2 using first-principles calculations. This material is theoretically optimized in the rhombohedral crystal structure system. The dynamical stability analysis shows that this material is dynamically unstable at ambient conditions but becomes stable under 2

It is quite intriguing to investigate the transition from a topological insulator (TI) phase to a topological crystalline insulator (TCI) phase in a material, as the latter has an advantage over the former in controlled device applications. This work investigates the existence of this dual topological behavior in the family of Sn-based ternary chalcogenides PbSnX2 (X = S, Se, Te) under hydrostatic pressure using a first-principles approach. These materials are dynamically stable at ambient and elevated pressure conditions, up to which the topological phase transitions (TPTs) are studied. This family has a topologically trivial ground state with direct band gap values 0.338, 0.183, and 0.217 eV for PbSnS2, PbSnSe2, and PbSnTe2, respectively. The first TPT, i.e., the TI phase, for these materials is observed under the effect of external pressures of 5, 2.5, and 3.5 GPa, with a single band inversion at the F point in the bulk band structure and an odd number of Dirac cones along the (111) surface. A further increase in pressures to 5.5, 3, and 4 GPa results in another band inversion at the Gamma point and an even number of Dirac cones along the (111) plane. The even number of band inversions suggest that the ( TCI phase is further corroborated by the even value of the mirror Chern number calculated using the winding of Wannier charge centers. 121) surface has mirror symmetry around the (10 1) plane, which confirms the existence of the TCI phase. This

By combining first-principles computations with the semi-classical Boltzmann transport equations, a systematic investigation of the structural, electronic and thermoelectric properties of the MoSSe Janus monolayer is conducted under pressure. The monolayer semiconducting nature is indicated by the band gap value (Eg = 1.5 eV), which may be further tuned from 0.56 to 1.67 eV by applying pressure in the -3GPa to + 2GPa range. The figure of merit (ZT) for p (n)-type carriers at 300 K in the absence of pressure is computed to be 0.67 and 0.59. The power factor has enhanced from 16.59 (27.21) Wm−1 K−2 to 227.15 (159.50) Wm−1 K−2 for n (p)-type carriers by applying an external pressure of -1 GPa to the Janus monolayer. For n (p) -type doping at 300 K, the corresponding maximum value of ZT is 0.82 (0.78), which is 39

Ferrimagnetic Heusler alloys show promising applications to thermoelectric and spintronic devices based on anomalous Nernst phenomena led by Berry curvature. The present work shows a computational investigation of the Anomalous Hall Conductivity (AHC) and Anomalous Nernst Conductivity (ANC) in a ferrimagnetic Cr2MnSb Heusler alloy, which exhibits both L21 and Xa structures. The spin-polarized calculations reveal that Cr2MnSb is a ferrimagnetic Heusler alloy, with a nearly zero magnetic moment. The nonzero large Berry curvature (Omega z (& Aring;2)) along the (001) plane leads to the large AHC value of 567 and 302 S cm-1 for L21 and Xa structure, respectively. The ANC value for L21 (0.80 Am-1 K-1) is significantly greater than Xa structure (0.05 Am-1 K-1) at room temperature. This value for L21 phase is further enhanced with B2 disorder because of a modification in the overall Berry curvature around the Fermi level. These large values of AHC and ANC in the L21 structure may be a consequence of the presence of mirror plane symmetry along . Therefore, Cr2MnSb, a ferrimagnetic material, can be a potential candidate for thermoelectric device applications with and without disorder.

We report the topological phase transition (TPT) in compounds of relatively less explored Zintl family RbZn4X3(X = P, As) viafirst-principlescalculation. These intermetallic compounds have already been experimentally synthesized in aKCu4S3-typetetragonal structure (P4/mmm) and reported to have a topologically trivial semimetallic nature with a direct band gap. We thoroughly studied the electronic structure, stability of RbZn4X3(X = P, As) and demonstrated the TPTs in these materials with external applied pressure and epitaxial strain. The dynamical and mechanical stabilities of these compounds are verified through phonon dispersion and Born stability criteria at ambient and TPT pressure/strain. A topologically non-trivial phase in RbZn4P3(RbZn4As3) is observed at 45 GPa (38 GPa) of hydrostatic pressure and 10% (8%) of epitaxial strain. This non-trivial phase is identified by band inversion betweenZn-sandP/As-pzorbitalsin the bulk band structure of these materials which is further confirmed using the surface density of states and Fermi arc contour in(001)-plane. The ℤ2topological invariants (ν0; ν1ν2ν3) for these materials are calculated using the product of parities of all filled bands (Kane and Mele model) and the evolution of Wannier charge centers (Wilson loop method). The change in values of (ν0; ν1ν2ν3) from (0; 000) to (1; 000), at the particular values of pressure and strain, is another signature of the TPT in these materials.

By means of hybrid density functional theory, we present the evolution of the topological phase in rare earth monopnictide YAs with hydrostatic pressure and epitaxial strain. This material exists in NaCl-type structure at ambient conditions and shows structural phase transition into CsCl-type structure at 56.54 GPa hydrostatic pressure. The epitaxial strain reduces the structure into a compressed tetragonal-type. The thermodynamical and dynamical stability of the material is established with the calculation of enthalpy and phonon band structure within structural phase transition, respectively. The topologically trivial phase of the material is observed at ambient pressure in agreement with previous reports. This material shows topological phase transition at 24.8 GPa applied hydrostatic pressure and 10% epitaxial strain. The band inversion at the X-point between d-Y and pAs orbitals is verified with the help of the product of parity analysis of all the filled bands. The presence of the Dirac cone in the (001) plane and the existence of topologically non-trivial states at M-point in the Fermi arc contour also established our claim. The Z(2) indices are calculated with the help of the product of parities and a change in Z(2) indices from (0; 000) to (1; 000) is also verified with the evolution of Wannier change centers under the conditions of applied hydrostatic pressure and epitaxial strain. The time reversal and inversion symmetries are preserved throughout the study and the topological phase transition at 24.8 GPa is much lower than the structural phase transition pressure i.e., 56.54 GPa.

The rare-earth monopnictide materials exhibiting topological properties have attracted considerable attention of condensed matter physicists. This article utilizes hybrid density functional theory to examine the structural stability, electronic properties, and topological phase characteristics of the rare-earth semimetal yttrium monophosphide (YP) when subjected to hydrostatic pressure. This material exhibits a stable face-centered cubic (NaCl-type) structure, which undergoes a structural phase transition at a hydrostatic pressure of 63.6 GPa. It is topologically trivial semimetal at ambient pressure but shows a topological phase transition at 26.5 GPa pressure. The topologically non-trivial phase in this material is substantiated via the band inversion at the X-point and the existence of the Dirac cone along the (001) plane. The product of parities at time-reversal invariant momenta points and the evolution of Wannier charge centers are used to calculate the & Zopf;2 topological invariants and obtain the values (1; 000) at 26.5 GPa.

We study the evolution of band topology under external pressure in rare-earth gadolinium mono-antimonide (GdSb) using first-principles calculations. This material crystallizes in a rocksalt-type structure and shows a structural phase transition (SPT) to a CsCl-type structure at 26.1 GPa. The phonon dispersions are analyzed to ascertain the dynamical stability of this material. We use hybrid density functional theory with the inclusion of spin-orbit coupling to investigate the structural, electronic, and topological phase transitions (TPTs). At ambient pressure, GdSb shows a topologically trivial state which is in agreement with existing experimental reports. The first TPT is observed at 6 GPa of hydrostatic pressure (at the high symmetry X-point) which is verified with the help of single-band inversion and surface state analysis along the (001) plane. The non-zero value of the first Z2 topological invariant and the presence of the Dirac cone also confirm the topological phase of this material. A further increase in pressure to 12 GPa results in two band inversions at Gamma- as well as X-points, which corresponds to the trivial nature of GdSb. The same is also verified with (0; 000) values of Z2 topological invariants and a pair of Dirac cones in surface states. It is noted that the crystal symmetries are preserved throughout the study and the TPT values are much lower than the SPT pressure, i.e. 26.1 GPa.

This work deals with the simulation of a perovskite solar cell with structure, ITO/SnO 2 /MAPbI[Formula: see text]Cl x /Spiro-MeOTAD/Ag using SCAPS-1D software. The optimization of absorber thickness and carriers’ lifetime results in [Formula: see text]% ([Formula: see text][Formula: see text]V, [Formula: see text][Formula: see text]mA/cm 2 and [Formula: see text]%). The same structures are also analyzed without ETL and HTL for making cost-effective solar cell. The efficiencies for both ETL and HTL free structures are found to be 17.42% and 9.98%, respectively. Further, the optimization of gradient doping shows a significant increment in performance parameters i.e. [Formula: see text]% ([Formula: see text][Formula: see text]V, [Formula: see text][Formula: see text]mA/cm 2 and [Formula: see text]%). Moreover, the analysis of various factors like average doping concentration, number of absorber sublayers, recombination velocities and temperature on the cell performance are performed to examine device stability. Present observations suggest that by considering only two sublayers, one can achieve the highest cell performance by using the gradient doping method. We have also validated the cell performance by comparing it with the experimental results and found a good agreement in both. Our findings may provide an effective route to fabricate highly efficient solar cell devices.

In this work, detailed theoretical elucidation on the structural stability and optoelectronic characteristics of the 1T-PdS2 monolayer is provided using density functional theory (DFT). The dynamical and mechanical stabilities of the structure are assessed through the analysis of phonon dispersion spectra and the Born-Huang stability criterion. The value of Young's modulus comes out to be 68.75 Nm(-1), which demonstrates high flexibility of the structure. Further, thermal stability of the structure is investigated using Ab-initio molecular dynamics simulations. The first-principle calculations by GGA + SOC (GGA + U) methods reveal that the monolayer is an indirect bandgap semiconductor having bandgap 1.14 eV (1.173 eV). The dielectric function displays its highest peak in the energy range 1.5-2 eV, whereas the maximum absorption coefficient lies in the ultraviolet region. Furthermore, the impact of vacancy defects are also investigated on the optoelectronic characteristics of the monolayer. The bandgap changes from indirect nature to direct one and reduces from 1.17 eV to 0.25 eV and 0.43 eV under single palladium and sulphur vacancies, respectively. The optical parameters also show enhancement with the introduction of these vacancies. The computational analysis reveals that 1T-PdS2 monolayer possesses advantageous attributes, making it a viable material for different optoelectronic applications.

Stacking engineering have played the very important role in tuning the structural, electronic and thermoelectric properties of 1 T ZrS 2 bilayer. All these calculations are performed by using first principles calculations in conjunction with the Boltzmann transport theory. The structural properties of bilayer with all possible stackings i.e., AA1, AA2, AA3, AB1, AB2 and AB3 along with their respective interlayer distance (d) are calculated. Electronic properties of these stacking bilayers have showed the indirect band gap in all the stacking pattern. The dynamical stability of AA1, AA2 and AA3 stackings are more in comparison to other stacking bilayers. The lattice thermal conductivity with values 0.57 W mK −1 , 0.47 W mK −1 and 1.45 W/mK for stackings AA1, AA2 and AA3, are obtained, respectively. The obtained values of ZT are 0.86, 0.83 and 0.82 for AA1, AA2 and AA3 stackings, respectively, at room temperature, for n-type doping. The present study has provided the effective approach for selecting the good stacking pattern of 1 T ZrS 2 bilayer for various applications with excellent thermoelectric performance.

This investigation employs ab-initio calculations to investigate the structural, dynamical, mechanical, and optoelectronic attributes of 1T-NiX2 (X = O, S, Se) monolayers. The confirmation of structural and dynamical stability is derived from negative cohesive energy values and the absence of negative frequencies in phonon dispersion spectra. Mechanical stability is established through the application of the Born-Huang stability criterion. Results indicate that an increase in the X-atom size from O to Se induces a reduction in material stiffness from 137.64 Nm−1 to 77.56 Nm−1 and thus, enhances the flexibility of the monolayers. The NiX2 monolayers exhibit indirect bandgap features with values 1.33 eV (1.81 eV), 0.63 eV (0.61 eV) and 0.28 eV (0.28 eV) using PBE (PBE+U) methods. Present results show an inverse relations between the band gap and the size of the X atom. The scanning tunneling microscope (STM) images of 2D NiX2 monolayers are also simulated for experimental observations. Additionally, exploration of optical characteristics reveals high optical absorption (105 cm−1), which lies from infrared to UV-region. Moreover, NiO2 can be utilized as good wave anti-reflectors with reflection of incident light less than 7%. These results suggest NiX2 materials as promising candidates for diverse applications in optoelectronic and photovoltaic devices.

In this article, a lead-free structure FTO/TiO2/NH3(CH2)2NH3MnCl4/spiro-OMeTAD/Au is investigated using SCPAS-1D simulator. Initially, impact of absorber thickness on performance is thoroughly examined and found 900 nm thick absorber solar cell superiuses performer (open circuit voltage = 1.18 V, short circuit current density = 24.47 mA/cm2, fill factor = 70.88

In this paper, the experimentally studied perovskite solar cell structure, ITO/SnO 2 /(FAPbI 3 )[Formula: see text] (MAPbBr[Formula: see text]Cl y ) x /Spiro-OMeTAD/Au, is considered as our primary cell structure. The Solar Cell Capacitance Simulator is used to investigate the cell performance. The cell performance is obtained after optimizing the influence of layer thickness (open circuit [Formula: see text][Formula: see text]V, short circuit [Formula: see text][Formula: see text]mA/cm 2 , fill [Formula: see text]%, power conversion [Formula: see text]%). In addition, various inorganic hole transporting layers are incorporated in place of Spiro-OMeTAD to improve cell stability and performance. Finally, with an open circuit [Formula: see text][Formula: see text]V, a short circuit [Formula: see text][Formula: see text]mA/cm 2 , a fill [Formula: see text]%, and a power conversion efficiency = 19.55%, the optimized cell structure i.e., ITO/SnO 2 /(FAPbI 3 )[Formula: see text](MAPbBr[Formula: see text]Cl y ) x /CulnSe 2 /Au, performs better. The cell performance is examined in relation to defect density in the absorber layer and at the layer interface. The primary cell results are also validated with the existing experimental results in the literature. This research will pave the way for the development of highly efficient mix-cation perovskite solar cells.

The present work deals with the simulation of lead-free germanium (Ge) based perovskite solar cell having structure: FTO/SnO2/MAGeI3/Spiro-OMeTAD/Au using one dimensional SCAPS simulator. Initially, the optimisations of absorber thickness and absorber defect density are performed to obtain an efficient and stable device structure. This optimisation results into higher conversation efficiency i.e., 25.34 % (Voc = 1.18 V, Jsc = 24.79 mA/cm2 and FF = 86.54 %). Further, the relations between optimised thickness and absorber defects are also verified and it is found that due to lower diffusion length of charge carriers, the optimised thickness decreases with increase in absorber defect.

This work investigates the structural, electronic, elastic, and transport properties of the AgSbS2 monolayer, using density functional theory in conjunction with semiclassical Boltzmann transport theory. In this study, we proposed a strategy to enhance the figure of merit (ZT) by optimizing the carrier concentrations. The monolayer of AgSbS2 is found to be both mechanically and thermodynamically stable. The phonon bandstructure and ab-initio molecular dynamics are also used to verify its excellent dynamical and thermal stability. The calculated electronic bandstructure shows a semiconducting nature of AgSbS2 with an indirect band gap of 1.31 eV using the Heyd-Scuderia-Ernzerhof (HSE06) exchange–correlation functional. The investigated monolayer is found to be anisotropic, hence we analyzed its thermoelectric properties at various carrier concentrations along a– and b–directions at 300 K. It attained a high value of Seebeck coefficient of 360 μVK−1 and 370 μVK−1 in the a– and b– directions at room temperature, respectively. The low thermal conductivity and high power factor result in an appreciable ZT value. The maximum ZT of AgSbS2 monolayer at an optimized carrier concentration of 2 × 1019 cm−3 is found to be 0.54 in the b-direction for the n-type monolayer at 300 K. The present work supports the potential use of AgSbS2 in room-temperature energy harvesting applications.