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Transition-metal borides (TMBs) have long attracted attention of the researchers because of their unique mechanical and electrical properties including superconductivity. We have explored the structural, mechanical, electronic, optical, and some thermophysical properties of XB$_2$ (X = Cr, Mo and W) binary metallic diborides in detail employing density functional theory based first-principles method. Many of the physical properties, including direction-dependent mechanical properties, optical properties, and thermo-mechanical properties are being investigated for the first time.

The physical properties and their pressure dependence of recently synthesized Ti2AlX (X = B, C, and N) MAX phases are investigated for the very first time applying density functional theory (DFT).

Double perovskite halides are promising materials for renewable energy production, meeting the criteria to address energy scarcity issues. As a result, studying these halides could be useful for optoelectronic and solar cell applications. In this study, we investigated the structural, mechanical, thermodynamic, electronic, and optical properties of A2AgIrCl6 (A = Cs, Rb, K) double perovskite halides using density functional theory calculations with the full-potential linearized augmented plane-wave (FP-LAPW) approach, aiming to evaluate their suitability for renewable energy devices. The Goldsmith tolerance factor, octahedral factor, and new tolerance factor have confirmed the cubic stability of the predicted compounds. We have also verified the thermodynamic stability of these compounds by calculating the formation enthalpy, binding energy, and phonon dispersion curves. Additionally, Born-Huang stability requirements on stiffness constants confirmed the mechanical stability of the titled compounds. To predict the accurate optoelectronic properties, we employed the TB-mBJ potential. The electronic band structure calculations revealed that the titled halides exhibit a direct band gap semiconducting nature with values of 1.43 eV, 1.50 eV, and 1.55 eV for Cs2AgIrCl6, Rb2AgIrCl6, and K2AgIrCl6, respectively. Besides, all these compounds showed remarkably low effective electron masses, indicating their potential for high carrier mobility. Furthermore, the optical properties of A2AgIrCl6 (A = Cs, Rb, K) compounds demonstrated very low reflectivity and excellent light absorption coefficients (105 cm-1) in the visible light spectrum, suggesting their suitability as an absorbing layer in solar cells. The photoconductivity and absorption spectra of these compounds validate the accuracy of our band structure results., Comment: 38 pages

First-principles investigation within the density functional theory is utilized to explore the physical properties of a superconducting topological semimetal Sn4Au under pressure within the range of 0-5 GPa. According to the computed elastic moduli, the compound under study is classified as ductile and applied pressure enhances the ductility. The compound has very high level of dry lubricity and machinability index. All the anisotropy factors demonstrate an elastically anisotropic nature. The electronic properties are investigated in view of the electronic band structure and density of states. The band structure reveals the topological semimetallic feature of Sn4Au while the density of states at the Fermi level decreases gradually with increasing pressure. Both ionic and covalent bondings are observed in Sn4Au. Optical parameters of Sn4Au are investigated at different pressures. The characteristic peaks in reflectivity, refractive index and photoconductivity exhibit a shift towards higher energy with increasing pressure for all polarizations of the electric field vector. The absorption coefficient and reflectivity spectra designate Sn4Au as a suitable system for optoelectronic applications. Moreover, the pressure dependent shifts in the electronic density of states at the Fermi level, the changes in the Debye temperature, and pressure induced variations in the repulsive Coulomb pseudopotential have been used to explore the effect of pressure on the superconducting transition temperature in this study.

In this study, using the density functional theory, we have investigated the bulk physical properties like structural, electronic band structure, elastic properties, thermal properties, optical properties and bonding features of AlPO4 compound in the hexagonal form. The values of our optimized structural parameters are very close to the previous results. Most of the results presented in this work are novel. The elastic constants indicate that AlPO4 is mechanically stable and brittle in nature. The compound is moderately hard and possesses low machinability index. AlPO4 contains significant elastic anisotropy. The charge density distribution , bond population analysis, Vickers hardness, thermo-mechanical properties, and optical properties have been investigated for the first time. The electronic band structure calculations reveal clear insulating behavior with a band gap of 6.0 eV. Band structure calculations were carried out without and with spin-orbit coupling (SOC) to explore possible topological signature. The energy dependent optical properties conform to the electronic band structure calculations. Major optical properties like dielectric functions, refractive index, photoconductivity, absorption coefficient, loss function and reflectivity are calculated and discussed in detail in this study. The compound is optically anisotropic. It is an efficient absorber and reflector of the ultraviolet light.

Rare-earth tritellurides (RTe3) are popular for their charge density wave (CDW) phase, magnetotransport properties and pressure induced superconducting state among other features. In this literature, Density functional theory has been exploited to study various properties of NdTe3. The calculated elastic and thermomechanical parameters, which were hitherto untouched for any RTe3, uncover soft, ductile, highly machinable and damage tolerant characteristics, as well as highly anisotropic mechanical behavior of this layered compound. Its thermomechanical properties make it a prospective thermal barrier coating material. Band structure, density of states, Fermi surfaces and various optical functions of the material have been reported. The band structure demonstrates highly directional metallic nature. The highly dispersive bands indicate very low effective charge carrier mass for the in-plane directions. The Fermi surfaces display symmetric pockets, including signs of nesting, bilayer splitting among others, corroborating previous works. The optical spectra expose high reflectivity across the visible region, while absorption is high in the ultraviolet region. Two plasma frequencies are noticed in the optical loss function. The optical conductivity, reflectivity and absorption reaffirm its metallic properties. The electronic band structure manifests evidence of CDW phase in the ground state., Comment: 20 pages, 6 figures

Learning from point sets is an essential component in many computer vision and machine learning applications. Native, unordered, and permutation invariant set structure space is challenging to model, particularly for point set classification under spatial deformations. Here we propose a framework for classifying point sets experiencing certain types of spatial deformations, with a particular emphasis on datasets featuring affine deformations. Our approach employs the Linear Optimal Transport (LOT) transform to obtain a linear embedding of set-structured data. Utilizing the mathematical properties of the LOT transform, we demonstrate its capacity to accommodate variations in point sets by constructing a convex data space, effectively simplifying point set classification problems. Our method, which employs a nearest-subspace algorithm in the LOT space, demonstrates label efficiency, non-iterative behavior, and requires no hyper-parameter tuning. It achieves competitive accuracies compared to state-of-the-art methods across various point set classification tasks. Furthermore, our approach exhibits robustness in out-of-distribution scenarios where training and test distributions vary in terms of deformation magnitudes.

We investigated the structural, elastic, electronic, vibrational, optical, thermodynamic and a number of thermophysical properties of W2N3 in this study using DFT based formalisms. The mechanical and dynamical stabilities have been confirmed. The Pugh and Poisson ratios are located quite close to the brittle to ductile borderline. The electronic band structure and energy density of states show metallic behavior. The Fermi surface features are investigated. The analysis of charge density distribution map clearly shows that W atoms have comparatively high electron density around than the N atoms. Presence of covalent bondings are anticipated. High melting temperature and high phonon thermal conductivity at room temperature of W2N3 imply that the compound has potential to be used as a heat sink system. The optical characteristics demonstrate anisotropy for W2N3. The compound can be used in optoelectronic device applications due to its high absorption coefficient and low reflectivity in the visible to ultraviolet spectrum. Furthermore, the quasiharmonic Debye model is used to examine temperature and pressure dependent thermal characteristics for the first time., Comment: Submitted to Journal of Alloys and Compounds

We have investigated the structural, elastic, electronic, thermophysical, superconducting, and optical properties of ScYH6 under uniform hydrostatic pressures up to 25 GPa, using the density functional theory (DFT) formalism. Most of results reported here are novel. The compound ScYH6 has been found to be elastically and thermodynamically stable within the pressure range considered. The compound is brittle; the brittleness decreases with increasing pressure. The elastic anisotropy is low and the machinability index is moderate which increases gradually with rising pressure. The compound is a hard material. The electronic band structure shows weakly metallic character with low density of states at the Fermi level. The Debye temperature of the compound is high and increases with increasing pressure. The Gr\"uneisen parameter of ScYH6 is low and the phonon thermal conductivity is high at room temperature. The compound is a very efficient reflector of infrared radiation. The compound is also an efficient absorber of visible and ultraviolet light. The overall effect of pressure on optical parameters is small. We have also investigated the pressure induced changes in the predicted superconducting state properties by considering the changes in the electronic density of states at the Fermi level, Debye temperature, and the repulsive Coulomb pseudopotential. The superconducting transition temperature is found to increase gradually with increasing pressure., Comment: arXiv admin note: text overlap with arXiv:2311.06709

In recent years, the investigation of novel materials for various technological applications has gained much importance in materials science research. Tri-molybdenum phosphide (Mo3P), a promising transition metal phosphide (TMP), has gathered significant attention due to its unique structural and electronic properties, which already make it potentially valuable system for catalytic and electronic device applications. Through an in-depth study using the density functional theory (DFT) calculations, this work aims to clarify the basic properties of the Mo3P compound at different pressures. In this work, we have studied the structural, elastic, optoelectronic and thermophysical properties of binary Mo3P compound. In this investigation, we varied uniform hydrostatic pressure from 0 GPa to 30 GPa. A complete geometrical optimization for structural parameters is performed and the obtained values are in good accord with the experimental values where available. It is also found that Mo3P possesses very low level of elastic anisotropy, reasonably good machinability, ductile nature, relatively high Vickers hardness, high Debye temperature and high melting temperature. Thermomechanical properties indicate that the compound has potential to be used as a thermal barrier coating material. The bonding nature in Mo3P has been explored. The electronic band structure shows that Mo3P has no band gap and exhibits conventional metallic behavior. All of the energy dependent optical characteristics demonstrate apparent metallic behavior and agree exactly with the electronic density of states calculations. The compound has excellent reflective and absorptive properties suitable for optical applications. Pressure dependent variations of the physical properties are explored and their possible link with superconductivity has been discussed.

Using the density functional theory (DFT) based first-principles investigation, the structural, mechanical, hardness, elastic anisotropy, optoelectronic, and thermal properties of cubic KB2H8 have been studied within the uniform pressure range of 0 - 24 GPa. The calculated structural parameters are in good agreement with the previous theoretical work. The compound KB2H8 is found to be structurally and thermodynamically stable in the pressure range from 8 GPa to 24 GPa. Single crystal elastic constants Cij and bulk elastic moduli (B, G and Y) increase systematically with pressure from 8 GPa to 24 GPa. In the stable phase, KB2H8 is moderately elastically anisotropic and ductile in nature. The compound is highly machinable and fracture resistant. The Debye temperature, melting temperature and thermal conductivity increases with pressure. The results of electronic band structure calculations and optical parameters at different pressures are consistent with each other. The compound is optically isotropic. The compound KB2H8 has potential to be used as a very efficient solar energy reflector. The electronic energy density of states at the Fermi level decreases systematically with increasing pressure. The same trend is found for the repulsive Coulomb pseudopotential. Possible relevance of the studied properties to superconductivity has also been discussed in this paper.

In this study, the effects of sulfur substitution on the structural, mechanical, electronic, optical, and thermodynamic properties of RbTaO3-xSx have been investigated using the WIEN2k code in the framework of density functional theory (DFT). The cubic phase of RbTaO3 transforms to tetragonal for RbTaO2S and RbTaOS2, the later transforms again to a cubic phase with added sulfur for RbTaS3. The results showed that substituting S for O anions in RbTaO3 effectively decreased the band gap from 2.717 eV to 1.438 eV, 0.286 eV, and 0.103 eV for the RbTaO3,RbTaO2S, RbTaOS2, and RbTaS3 compounds, respectively. The optical constants such as dielectric constants, refractive index, absorption coefficient, photoconductivity, reflectivity and loss function have been calculated and analyzed. The elastic constants and moduli, and their anisotropic nature were also investigated. Finally, the Debye temperature, thermal conductivity, melting temperature, specific capacities and thermal expansion coefficients were computed and analyzed using established formalisms. The reduced band gap (1.438 eV) and high absorption coefficient (~106 cm-1) of RbTaO2S makes it suitable for solar cell applications and for other visible light devices. Reduction of the band gap and phonon thermal conductivity owing to Ssubstitution is expected to enhance thermoelectric performances of the S-containing phases, Comment: 41 pages

Here we report the structural, elastic, bonding, thermo-mechanical, optoelectronic and superconducting state properties of recently discovered XIr3 (X = La, Th) superconductors utilizing the density functional theory (DFT). The elastic, bonding, thermal and optical properties of these compounds are investigated for the first time. The calculated lattice and superconducting state parameters are in reasonable agreement to those found in the literature. In the ground state, both the compounds are mechanically stable and possess highly ductile character, high machinability, low Debye temperature, low bond hardness and significantly high melting point. The thermal conductivities of the compounds are found to be very low which suggests that they can be used for thermal insulation purpose. The population analysis and charge density distribution map confirm the presence of both ionic and covalent bonds in the compounds with ionic bond playing dominant roles. The calculated band structure and DOS profiles indicate metallic character. Unlike the significant anisotropy observed in elastic and thermal properties, all the optical constants of these compounds exhibit almost isotropic behavior. The optical constants correspond very well with the electronic band structure and DOS features. We have estimated the superconducting transition temperature of the compounds in this work.

In this study, we looked into a number of physical properties of alkali-bismuth compounds KBi$_2$ and RbBi$_2$ in the cubic Laves phase using the density functional theory (DFT). The structural, elastic, anisotropy indices, hardness, thermo-physical parameters, electronic band structure, and optoelectronic properties have been explored. Most of the results presented in this work are novel in nature.

Here we describe a new image representation technique based on the mathematics of transport and optimal transport. The method relies on the combination of the well-known Radon transform for images and a recent signal representation method called the Signed Cumulative Distribution Transform. The newly proposed method generalizes previous transport-related image representation methods to arbitrary functions (images), and thus can be used in more applications. We describe the new transform, and some of its mathematical properties and demonstrate its ability to partition image classes with real and simulated data. In comparison to existing transport transform methods, as well as deep learning-based classification methods, the new transform more accurately represents the information content of signed images, and thus can be used to obtain higher classification accuracies. The implementation of the proposed method in Python language is integrated as a part of the software package PyTransKit, available on Github.

We have looked into the structural, mechanical, optoelectronic, superconducting state and thermophysical aspects of intermetallic compound Zr$_3$Ir using the density functional theory (DFT). Many of the physical properties, including direction dependent mechanical properties, Vickers hardness, optical properties, chemical bonding nature, and charge density distributions, are being investigated for the first time. According to this study, Zr$_3$Ir exhibits ductile features, high machinability, significant metallic bonding, a low Vickers hardness with low Debye temperature, and a modest level of elastic anisotropy. The mechanical and dynamical stabilities of Zr$_3$Ir have been confirmed. The metallic nature of Zr$_3$Ir is seen in the electronic band structures with a high electronic energy density of states at the Fermi level. The bonding nature has been explored by the charge density mapping and bond population analysis. The tetragonal Zr$_3$Ir shows a remarkable electronic stability, as confirmed by the presence of a pseudogap in the electronic energy density of states at the Fermi level between the bonding and antibonding states. Optical parameters show very good agreement with the electronic properties. The reflectivity spectra reveal that Zr$_3$Ir is a good reflector in the infrared and near-visible regions. Zr$_3$Ir is an excellent ultra-violet (UV) radiation absorber. High refractive index at visible photon energies indicates that Zr$_3$Ir could be used to improve the visual aspects of electronic displays. All the optical constants exhibit a moderate degree of anisotropy. Zr$_3$Ir has a moderate melting point, high damage tolerance, and very low minimum thermal conductivity. The thermomechanical characteristics of Zr$_3$Ir reveal that it is a potential thermal barrier coating material. The superconducting state parameters of Zr$_3$Ir are also explored.

At the core of each blockchain system, parties communicate through a peer-to-peer (P2P) overlay. Unfortunately, recent evidence suggests these P2P overlays represent a significant bottleneck for transaction throughput and scalability. Furthermore, they enable a number of attacks. We argue that these performance and security problems arise because current P2P overlays cannot fully capture the complexity of a blockchain system as they do not offer flexibility to accommodate node heterogeneity. We propose a novel approach to address these issues: P2P Overlay Domains with Sovereignty (PODS), which allows nodes in a single overlay to belong to multiple heterogeneous groups, called domains. Each domain features its own set of protocols, tailored to the characteristics and needs of its nodes. To demonstrate the effectiveness of PODS, we design and implement two novel node discovery protocols: FedKad and SovKad. Using a custom simulator, we show that node discovery using PODS (SovKad) architecture outperforms both single overlay (Kademlia) and multi-overlay (FedKad) architectures in terms of hop count and success rate, though FedKad requires slightly less bandwidth.

In this work, density functional theory (DFT) based calculations were performed to compute the physical properties (structural stability, mechanical behavior, electronic, thermodynamic, and optical properties) of synthesized MAX phases Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, Hf2TeB, and the as-yet-undiscovered MAX carbide phase Hf2TeC. Calculations of formation energy, phonon dispersion curves, and elastic constants confirmed the stability of the aforementioned compounds. The obtained values of lattice parameters, elastic constants, and elastic moduli of Hf2SB, Hf2SC, Hf2SeB, Hf2SeC, and Hf2TeB showed fair agreement with earlier studies, whereas the values of the mentioned parameters for the predicted Hf2TeC exhibit a good consequence of B replacement by C. The anisotropic mechanical properties are exhibited by the considered MAX phases. The metallic nature and its anisotropic behavior were revealed by the electronic band structure and density of states. The analysis of the thermal properties Debye temperature, melting temperature, minimum thermal conductivity, and Gruneisen parameter confirmed that the carbide phases were more suited than the boride phases considered herein. The MAX phase response to incoming photons further demonstrated that they were metallic. Their suitability for use as coating materials to prevent solar heating was demonstrated by the reflectivity spectra. Additionally, this study demonstrated the impact of B replacing C in the MAX phases., Comment: 38 pages

Binary uranium hydrides, UHx (x = 1, 2, 3, 5, 6, 7, 8), with different crystal symmetries are potentially interesting compounds for high-Tc superconductivity and as hydrogen storage systems. In this work we have explored the structural, elastic, mechanical, bonding, and thermophysical properties of these systems under uniform pressure via density functional theory based computations. Most of the results disclosed in this work are novel. From the calculations of the cohesive energy and enthalpy of formation, we have found that the titled compounds are chemically stable. The computed elastic constants at different pressures ensure elastic stability. All the binary hydrides are mechanically anisotropic. Pressure induced brittle-ductile transition takes place under high pressure. The compounds are machinable with the cubic {\alpha}-UH3-Pm-3n showing very high value of the machinability index. All the compounds are fairly hard with cubic UH8 showing superhard character. The Debye temperatures and acoustic velocities of these compounds are high; the highest value is found for the cubic UH8. The melting temperature, Gr\"uneisen parameter, minimal phonon thermal conductivity, and the thermal expansion coefficient of these compounds have also been studied at different pressures. All these parameters show excellent correspondence with the estimated Debye temperature, elastic parameters and bonding characteristics., Comment: arXiv admin note: text overlap with arXiv:2211.09457

In this study, we have used density functional theory (DFT) based first-principles investigation of the physical properties of prospective NbAlB compound for the first time. From the analysis of the cohesive energy and enthalpy of formation, it was found that NbAlB is chemically stable. The physical properties of NbAlB have been compared and contrasted with those obtained for MoAlB. Both these MAB phases are elastically anisotropic, mechanically stable, machinable and brittle materials. Structural and elastic features reflect the layered features. The estimated hardness of NbAlB is 19.0 GPa comparable to that of MoAlB (20.8 GPa) suggesting that predicted NbAlB is a hard compound and is suitable for heavy duty industrial applications. NbAlB is more machinable than MoAlB. Electronic band structure calculations reveal conventional metallic behavior with the electronic density of states at the Fermi level arising mainly due to the Nb 4d orbitals in NbAlB. The electronic density of states at the Fermi level is significantly higher in NbAlB in comparison to MoAlB, indicating that NbAlB is expected to exhibit higher level of electrical conductivity. Electronic dispersion is highly anisotropic for both MoAlB and NbAlB with substantially large electronic effective masses in the out-of-plane directions. The bonding features have been elucidated via the analysis of the band structure and charge density distribution. Both the compounds have mixed covalent, ionic and metallic bonding characteristics. The Fermi surfaces of MoAlB and NbAlB consists of electron and hole like sheets. The Debye temperatures of MoAlB and NbAlB are comparable. The estimated melting temperature of NbAlB is somewhat lower than that of MoAlB. NbAlB shows excellent reflection characteristics suitable to be used as an efficient solar reflector. NbAlB is also expected to absorb ultraviolet radiation very effectively.

BaAgAs is a ternary Dirac semimetal which can be tuned across a number of topological orders. In this study we have investigated the bulk physical properties of BaAgAs using density functional theory based computations. Most of the results presented in this work are novel. The optimized structural parameters are in good agreement with previous results. The elastic constants indicate that BaAgAs is mechanically stable and brittle in nature. The compound is moderately hard and possesses fair degree of machinability. There is significant mechanical/elastic anisotropy in BaAgAs. The Debye temperature of the compound is medium and the phonon thermal conductivity and melting temperature are moderate as well. The bonding character is mixed with notable covalent contribution. The electronic band structure calculations reveal clear semimetallic behavior with a Dirac node at the Fermi level. BaAgAs has a small ellipsoidal Fermi surface centered at the G-point of the Brillouin zone. The phonon dispersion curves show dynamical stability. There is a clear phonon band gap between the acoustic and the optical branches. The energy dependent optical constants conform to the band structure calculations. The compound is an efficient absorber of the ultraviolet light and has potential to be used as an anti-reflection coating. Optical anisotropy of BaAgAs is moderate. The computed repulsive Coulomb pseudopotential is low indicating that the electronic correlations in this compound are not strong., Comment: Submitted for publication. arXiv admin note: text overlap with arXiv:2303.01319

In this paper, we have presented a comprehensive study of the physical properties of Kagome superconductor CsV3Sb5 using the density functional theory (DFT). The structural, mechanical, electronic, atomic bonding, hardness, thermodynamic, and optical properties, and their pressure dependences have been investigated for the first time. The calculated ground state lattice parameters and volume are in excellent agreement with available experimental results. The estimated single-crystal elastic constants ensured the mechanical stability of the compound, whereas phonon spectra endorse dynamical stability at zero pressure. The electronic band structure, energy density of states, optical properties confirmed the metallic features. The Pugh ratio, Poisson's ratio of the compound revealed softness and ductility. The hardness, estimated from several formulae, is quite low while the machinability index predicted good machinability with excellent dry lubricating properties. The compound shows tendency towards structural instability at a pressure around 18 GPa. The optical constants have also been studied to correlate those with electronic properties and to predict possible applications of this compound. Both mechanical and optical properties show anisotropy.CsV3Sb5 is predicted to be an efficient absorber of ultraviolet radiation. The compound is also an efficient reflector of visible light.

PbTaSe2 is a non-centrosymmetric topological semimetal. In this work we have explored the structural, elastic, mechanical, bonding, electronic, acoustic, thermal, and optical properties of PbTaSe2. The electronic bond structure calculations confirm semi-metallic character. Fermi surface topology shows both electron and hole sheets. The single crystal elastic constants reveal that PbTaSe2 is elastically stable. The compound is soft, brittle, and highly machinable at the same time. It also possesses very high level of dry lubricity. Various anisotropy indicators suggest that PbTaSe2 is elastically anisotropic with layered character. The phonon dynamics has been investigated. Phonon dispersion plot shows that the compound is dynamically stable with a clear frequency gap between the acoustic and optical branches. The Debye temperature, phonon thermal conductivity, and melting temperature of PbTaSe2 is low. The compound has medium Gr\"uneisen parameter. The bonding character is mainly dominated by ionic bonding with some metallic contribution. The optical parameters have been studied in detail. The optical spectra reveal metallic features. The compound reflects visible light very efficiently (reflectance above 60%). It is also an efficient absorber of the ultraviolet light. The compound exhibits significant optical anisotropy with respect to the polarization directions of the incident electric field.

The effects of hole content (p) and oxygen deficiency (delta) on the zero-field critical current density, Jc0, were investigated for high-quality c-axis oriented Y1-xCaxBa2Cu3O7-delta (x = 0, 0.05, 0.10, and 0.20) thin films. Low temperature critical current density of these films above the optimum doping were found to be high and were primarily determined by the hole concentration, reaching a maximum at p ~ 0.185 +/- 0.005, irrespective of the level of oxygen deficiency. This implies that oxygen disorder plays only a secondary role and the intrinsic Jc0 is primarily governed by the carrier concentration in the copper oxide planes. Further support in favor of this was found from the analysis of the in-plane resistive transitions of c-axis oriented crystalline thin films of YBa2Cu3O7-delta (YBCO) under magnetic fields (H) applied along the c-direction, over a wide range of doped holes. The characteristic magnetic field (H0), linked to the vortex activation energy and the irreversibility field, exhibits similar p-dependence as shown by Jc0(p). We have explained these observations in terms of the doping dependent pseudogap (PG) in the low-energy electronic energy density of states. Both the intrinsic critical current density and the irreversibility field depend directly on the superconducting condensation energy, which in turn is largely controlled by the magnitude of the hole concentration dependent PG in the quasiparticle spectral density., Comment: Submitted to Superconductivity

Here we have used the density functional theory (DFT) with the GGA-PBE approximation to investigate the structural, mechanical, electronic, hardness, thermal, superconductivity and optoelectronic properties under pressure for monoclinic (P21/m) and orthorhombic (Pmn21) structures of MgVH6. We have studied optical properties of P21/m phase at 0 GPa and Pmn21 phase at 100 GPa only (considering phase stability). Both of the phases of MgVH6 are thermodynamically stable. P21/m phase is mechanically stable but Pmn21 is mechanically unstable in our calculations for the pressures considered. Monoclinic (P21/m) is ductile in nature, on the other hand, orthorhombic (Pmn21) is brittle in nature at 100 GPa and becomes ductile for pressures in the range from 125 GPa to 200 GPa. Hardness calculations indicate superhard character of orthorhombic (Pmn21) structure at 100 GPa. The melting temperature of orthorhombic crystal is very high. This also agrees with the bulk modulus, Debye temperature, and hardness calculations. We have calculated theoretically the superconducting transition temperature Tc at different pressures only for the orthorhombic (Pmn21) structure following a previous study. The estimated values of transition temperatures are within 104.7 K to 26.1 K in the pressure range from 100 GPa to 200 GPa. MgVH6, in both the structures, are elastically and optically anisotropic.

We present a detailed density functional theory based calculations of the structural, elastic, lattice dynamical, thermophysical, and optoelectronic properties of ternary semiconductors CaZn$_2$X$_2$ (X = N, P, As) in this paper. The obtained lattice parameters are in excellent agreement with the experimental values and other theoretical findings. These elastic constants satisfy the mechanical stability criteria. Moreover, many thermophysical parameters of these compounds are estimated, including the Debye temperature, average sound velocity, melting temperature, heat capacity, lattice thermal conductivity, etc. The comprehensive analysis of the elastic constants and moduli show that CaZn$_2$X$_2$ compounds possess reasonably good machinability, relatively high Vickers hardness and relatively low Debye temperature. The phonon dispersion curves and phonon density of states are investigated for the first time for the compounds CaZn$_2$P$_2$ and CaZn$_2$As$_2$. It is observed from the phonon dispersion curves that the bulk CaZn$_2$X$_2$ (X = N, P, As) compounds are dynamically stable. Electronic properties have been studied through the band structures and electronic energy density of states. The electronic band structures show that CaZn$_2$N$_2$ and CaZn$_2$As$_2$ possess direct band gaps while the compound CaZn$_2$P$_2$ show indirect band gap. The bonding characters of CaZn$_2$X$_2$ (X = N, P, As) compounds are investigated. Energy dependent optical parameters exhibit good correspondence with the electronic energy density of states features. We have thoroughly discussed the reflectivity, absorption coefficient, refractive index, dielectric function, optical conductivity and loss function of these semiconductors. The optical absorption, reflectivity spectra and the refractive index of CaZn$_2$X$_2$ (X = N, P, As) show that the compounds hold promise to be used in optoelectronic devices.

Density functional theory based study of the pressure dependent physical properties of binary SnS compound has been carried out. The computed elastic constants reveal that SnS is mechanically stable and brittle under ambient conditions. With increasing pressure, the compound becomes ductile. The Poisson's ratio also indicates brittle-ductile transition with increasing pressure. The hardness of SnS increases significantly with pressure. The compound possesses elastic anisotropy. The ground state electronic band structure is semiconducting with a small band gap which becomes metallic under pressure. The band becomes more and more dispersive with the increase in pressure while the electronic correlations decrease as pressure is raised. Both the Debye temperature and the phonon thermal conductivity of SnS increase sharply with pressure. The Melting temperature of the compound is low. Mixed bonding characteristics are found with ionic and covalent contributions. SnS is a good absorber of ultraviolet light. The reflectivity of the material increases with the increase in pressure. The reflectivity is nonselective over a wide spectral range. The low energy refractive index is high. All these optical characteristics are useful for prospective optoelectronic device applications. The optical anisotropy is low.

Binary metallic carbides belong to a technologically prominent class of materials. We have explored the structural, mechanical, electronic, optical, and some thermophysical properties of XC (X = Nb, Ta, Ti) binary metallic carbides in details employing first-principles method. Some of the results obtained are novel. A comparative analysis has been made.

ZrNCl and HfNCl belong to a class of layered transition metal nitride halides MNCl (M= Zr,H). They are from the space group R-3m (No-166) and crystallize in the rhombohedral structure. Both of these materials have shown promising semiconducting behaviors. Recent studies have shown their versatility as semiconductors and also as superconductors when intercalated with alkaline metals. This paper explores the mechanical, optical and electronic properties of these two semiconducting crystals in depth. A comparative study between the two materials in their elastic constants, anisotropy measures, electronic density of states and band structures, optical spectra has been performed with first principles density functional theory (DFT) based calculations within the local density approximation (with appropriate U for the energy gap calculations in case of HfNCl). HfNCl is more machinable than ZrNCl and is relatively softer as indicated by the lower Debye temperature. ZrNCl has stronger layering due to which it exhibits brittle nature. HfNCl has a larger band gap. ZrNCl is a better reflector of ultraviolet radiation. On the other hand HfNCl is a good ultraviolet absorber. Both materials are anisotropic in regards to structure, electronic energy dispersion and optical parameters. Overall, the degree of anisotropy is more prominent in ZrNCl compared to that in HfNCl. Possible sectors for applications of ZrNCl and HfNCl semiconductors are discussed.

An interesting class of ternary metallic borides, known as the 212 MAX phase borides, is the recent advancement of the MAX phase family. In this article, results from ab-initio calculations on unexplored Ti$_2$PB$_2$, Zr$_2$PbB$_2$, and Nb$_2$AB$_2$ [A = P, S] are reported wherein Ti$_2$PB$_2$ along with its 211 boride phase Ti$_2$PB are predicted for the first time. The stability was confirmed by calculating the formation energy, phonon dispersion curve, and elastic stiffness constants. The obtained elastic constants, elastic moduli, and Vickers hardness values of Ti$_2$PB$_2$, Zr$_2$PbB$_2$, and Nb$_2$AB$_2$ [A = P, S] were found to be significantly larger than those of their counterparts 211 borides and carbides, in a trend similar to other 212 borides. The studied compounds are brittle like most of the MAX and MAB phases. The electronic band structure and density of states revealed the metallic nature of the titled borides. Several thermal parameters were explored, certifying the suitability of Ti2PB2, Zr2PbB2, and Nb2AB2 [A = P, S] compared to their counterparts, and a similar trend was found for the other 212 borides. The obtained results predict that Ti2PB2, Zr2PbB2, and Nb2AB2 [A = P, S] have significant potential for use as efficient thermal barrier coating materials. The response of Ti$_2$PB$_2$, Zr$_2$PbB$_2$, and Nb$_2$AB$_2$ [A = P, S] to the incident photon was studied by computing the dielectric constant (real and imaginary part), refractive index, absorption coefficient, photoconductivity, reflectivity, and energy loss function. The ability to protect from solar heating was revealed from the studied reflectivity spectra. In this work, we have explored the physical basis of the improved thermo-mechanical properties of 212 MAX phase borides compared to their carbide and boride counterparts., Comment: 36 pages

A large number of hitherto unexplored elastic, thermophysical, acoustic, and optoelectronic properties of a double Weyl semimetal SrSi2 have been investigated in this study. Density functional theory (DFT) based methodology has been employed. Analyses of computed elastic parameters reveal that SrSi2 is a mechanically stable, ductile, moderately machinable, and relatively soft material. The compound is predicted to be dynamically stable and possesses significant metallic bonding. Study of thermophysical properties, namely, Debye temperature, Gr\"uneisen parameter, acoustic parameters, melting temperature, heat capacity, thermal expansion coefficient, and dominant phonon mode is also indicative of soft nature of SrSi2. The electronic band structure calculations without and with spin-orbit coupling disclose semimetallic character with clear Weyl nodes close to the Fermi level. The electronic dispersion is anisotropic characterized by nearly flat and linear regions within the Brillouin zone. Optical parameters at different photon energies are investigated. SrSi2 shows excellent nonselective reflection spectrum across an extended range of energy encompassing the visible region implying that the compound under study has significant potential to be used as an efficient solar energy reflector. SrSi2 absorbs ultraviolet light quite efficiently. The compound also possesses high refractive index in the low energy. All these optical features can be useful in optoelectronic device applications.

Fracture is a very challenging and complicated problem with various applications in engineering and physics. Although it has been extensively studied within the context of mesh-based numerical techniques, such as the finite element method (FEM), the research activity within the Smoothed Particle Hydrodynamics (SPH) community remains scarce. SPH is a particle-based numerical method used to discretize equations of continuum media. Its meshfree nature makes it ideal to simulate fracture scenarios that involve extreme deformations. However, to model fracture, SPH researchers have mostly relied on ad-hoc empirical local damage models, cohesive zone approaches, or pseudo-spring models, which come with a set of drawbacks and limitations. On the other hand, phase field models of brittle fracture have recently gained popularity in academic circles and provide significant improvements compared to previous approaches. These improvements include the derivation from fundamental fracture theories, the introduction of non-locality, and the ability to model multiple crack initiation, propagation, branching, and coalescence, in situations where no prior knowledge of the crack paths is available. Nevertheless, phase field for fracture has not been studied within SPH. In this proof-of-concept paper we develop and implement a phase field model of brittle fracture within the context of SPH. Comprehensive mathematical and implementation details are provided, and several challenging numerical examples are computed and illustrate the proposed method's ability to accurately and efficiently simulate complex fracture scenarios.