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We have investigated the structural, magneto-resistive, electrical, and thermal transport properties of monovalent substituted polycrystalline Nd0.7Sr0.3−xAxMnO3 (x = 0, 0.1 and A = Na, Ag, K) compounds. The Rietveld refinement of the X-ray diffraction patterns reveals that all samples crystallize in orthorhombic structure with Pnma space group. The scanning electron microscopy micrographs evidenced that the grains acquire uniform morphology, nearly spherical, and unequal grains in all the studied samples. The decrease in metal-insulator transition temperature on the monovalent substitution is a result of reduced double-exchange interactions. Further, above the metal-insulator transition, electrical transport properties are analyzed through variable range hopping and small polaron hopping models. The substitution of monovalent cations enhanced the experimental parameters like hopping distance and activation energy, while the density of state at the Fermi level decreased significantly. On the monovalent doping, the samples showed very high magnetoresistance (MR%), and the temperature coefficient of resistance (TCR%) makes them prospective candidates for advanced uncooled infrared bolometers. The thermoelectric power (S) demonstrates a positive to a negative crossover, and the value of S increased in doped samples. At the higher temperatures, the small polaron is responsible for the conduction process.

Structural and magnetic behavior of a series of new cobaltite Y1-xYbxBaCo4O7 (0 ≤ x ≤ 0.5), prepared using the conventional solid state reaction method have been investigated. Increasing Yb...

The environment and the health of the masses are being affected by toxic gases such as O3, SO3, CH2O, H2S and HCN. In this study, we investigate the interaction of such toxic gases on SnS monolayer using density functional theory (DFT). The interaction between species and adsorbent is explained on the basis of their adsorption energy, electronic properties and charge transfer. Our results demonstrate that the process of adsorption of O3 and SO3 is chemisorbed in nature whereas CH2O, H2S and HCN is physisorbed. The validity of the adsorption process is further confirmed within the frame of electronic properties and charge transfer. As a result, we find each of the investigated gas molecules is acting as a charge acceptor. Diversity in the adsorption of customary gas molecules on the SnS monolayer gives rise to a possibility to exploit them as chemical gas sensors.

In the present density functional theory based study, we have investigated the interfacial electronic properties and adsorption curve along with chemical bonding with interface of MoS2/SrO. Our calculations indicates that the electronic properties are highly interface dependent as the heterostructure (HS) shows metallic behavior in MoS2/SrO interface. The equilibrium interlayer distance deq between MoS2 and SrTiO3 (STO) is found within 2.62 to 2.67 . From our adsorption curve analysis, we have found that MoS2 is chemisorbed over STO substrate. Chemical bonds at the interface shows ionic bonding in MoS2/SrO interface. A unique behavior of cubic confined MoS2 monolayer is also observed in our investigation i.e. an indirect band gap of ∼1.63 eV is found. This behavior may lead to fabricate and investigate Si in the form of hexagonal honeycomb like monolayer which could present a direct band gap. Conclusively we can use the above investigated HS in metallic applications.

Carbon allotropes are known to be promising materials as chemical gas sensors. Proper modification in the electronic structure is required using suitable heteroatom doping to acquire better sensing property. We present the homonuclear B2 (B B) and B3 (B B B) doped carbon allotropes for the detection of toxic gases such as NO2, CO2, NH3, H2S and CO using the density functional theory. The sensitivity and selectivity of pure and boron doped C60 surfaces towards toxic gas molecules are estimated. With a new perception, the gas sensitivity has been correlated with π electron occupancy of the host materials. The adsorption behaviour of toxic gases on the host surface during the presence of H2O, O2 and O molecule/atom is estimated. The concept of homonuclear B sites is extended to 585 divacancy graphene and 585 divacancy carbon nanotube (CNT) system and verified that the phenomena are general for sp2 hybridized carbon allotrope. We also tested the CO oxidation and CO2 hydrogenation on B2 and B3 doped: C60 cage, 585 DV graphene and 585 DV CNT. The CO oxidation occurs via Langmuir–Hinshelwood (LH) mechanism. Overall we have found that the presence of homonuclear bond can change the inert carbon allotropes into highly active sensor material.

This report presents the structural, magnetoresistance, electrical and thermal transport properties of Aluminium substituted La 0.7 Ba 0.3 Mn 1−x Al x O 3 (0 ≤ x ≤ 0.15) compounds synthesized by solid state reaction method. To obtain crystallographic parameters, the X-ray diffraction patterns are fitted in R-3c space group with Rietveld refinement method. The resistivity and magneto-transport measurements are performed using standard four-probe assembly with and without magnetic fields. The peak resistivity ρ peak is noted at Metal-Insulator Transition temperature ( T MI ) and lowering in T MI is observed for higher concentrations of Al 3+ . The resistivity data have been analyzed in two parts. Firstly, in the metallic region below T MI the resistivity data is fitted with three degree polynomial. Secondly, in the semiconducting region above T MI data have been fitted with Variable Range Hopping (VRH) and Small Polaron Hopping (SPH) models. The Seebeck coefficients found to be positive throughout the temperature range (10 K–300 K) with holes as dominating charge carriers. Similar to the resistivity profile, in metallic region the thermo-power is explained with qualitative model based on diffusion, magnon-drag, phonon-drag and spin fluctuation contributions whereas the semiconducting region is explained with small polaron hopping model.

Using first principles density functional theory, we have studied the interaction mechanism of NO2 and SO2 gas molecules on an MoB2 monolayer, for gas sensing applications. The selectivity for a particular gas by the sensor has been analyzed through electronic structure calculations and adsorption studies. The calculations have been performed by considering the fact that the MoB2 monolayer as a sensing material encounters a change in its electrical properties, when gas molecules with different orientations get adsorbed on the surface. From the density of states study, we find better selectivity for NO2 as compared to SO2, as the latter leaves the electronic structure of the sensing material unaffected. Further, the adsorption curves support the above fact as the larger value of adsorption energy (Ead ∼ −1 eV) for NO2 indicates stronger adsorption. The chemisorptive nature for NO2, in contrast with the relatively weaker physisorption for SO2, additionally supports the fact that NO2 gas has a better perspective for MoB2 sensor application. Charge density plots for each case are in good agreement with the above conclusions. The faster recovery time attributes the MoB2 monolayer better as a sensor material for NO2 interaction.

In the present paper we have studied the effect of Sm doping on the magnetic and magnetocaloric properties of La 0.7-x Sm x Ba 0.3 MnO 3 (0 ≤ x ≤ 0.2) compounds. These sample have been synthesized by conventional solid state reaction method. The analysis of synthesized samples by X-ray diffraction showed that the formation of single phase compositions and doping of La 3+ by Sm 3+ ion converted the chemical structure form rhombohedral ( R-3C ) to orthorhombic ( Imma ). The magnetic study measurement specified that the ferromagnetic double exchange interaction is weakened with increasing Sm content as a consequence of the curie temperature (T c ) shift in lower temperature from 340 K for x = 0, 290 K for x = 0.1 and 225 K for x = 0.2 compounds. Using the Banerjee’s criterion plots, it is found that the phase transition for all samples in the second-order. All reported compounds exhibit a maximum and large magneto-caloric effect near the Curie temperature (T c ). The magnitude of the maximum magnetic entropy change is found to be decrease with increasing of Sm doping content i.e. 4.39 J/kg K for x = 0, 4.22 J/kg K for x = 0.1 and 2.48 J/kg K for x = 0.2 in applied field change of 5T. The trend of large entropy change and the convenient adjustment of the Curie temperature make these oxides useful for magnetic refrigeration in an extended high and low temperature even at near room temperature.

In the present paper we studied the structural, magnetotransport and thermopower properties of a series of polycrystalline La 0.7−x Sm x Ba 0.3 MnO 3 (0≤x≤0.2) compounds which were synthesized by conventional solid state reaction techniques. The Rietveld refinement of the X-ray diffraction pattern predicts the formation of single-phase compositions and doping of La 3+ by Sm 3+ ion converted the chemical structure form rhombohedral ( R-3C ) to orthorhombic ( Imma ) The scanning electron microscopy show clean smooth and densified structure images be a sign of good crystalline nature of the samples. The temperature dependent electrical resistivity is measured by standard four-probe method between 5 and 300 K exhibits Metal–Insulator Transition MIT which shows the decreasing trend with increasing Sm doping content and metallic state (T p2 ) that signifies importance of electron-electron, electron–phonon and electron-spin fluctuation scattering process. The metal–insulator transition temperature (T p2 ) is observed which decreases with the increase in doping content when magnetic field is applied. The resistivity data in high temperature region (T>T p2 ) are explained within the framework of variable range hopping (VRH) and small polaron hopping (SPH) models. The application of magnetic field suppresses the resistivity in entire temperature range and with increasing the Sm 3+ content the samples showed very high magnetoresistance. The thermoelectric power (S) of the reported samples exhibit a crossover from positive to negative value and it increases in doped samples. The analysis of thermoelectric power data confirms the applicability of the small polaron hopping model in high temperature region and in low temperature fitted to an equation containing diffusion, magnon drag, phonon drag and electron-spin fluctuation term. An appropriate justification for the observed behavior is specified.

The optical parameters and charge transfer analysis of MoB2 monolayer has been performed under the framework of density functional theory. A detailed study of optical properties including real and imaginary part of dielectric constant along with refractive index in x-, y- and z-direction witnessed a suppression along z-axis due to the broken symmetry in presence of 2-dimensional lattice arrangement. Our results suggest that MoB2 monolayer is metallic in nature which is found in agreement with available reports. In x- and y-directions the parameters are giving somewhat similar trend with respect to photon energy. Moreover we have studied the charge transfer mechanism with help of 3D Laplacian plots and Lowdin’s charge analysis. A strong intra-layer charge sharing is observed in B-atoms while some charge transfer was observed in inter-layer atomic species as well.

Ni-doped cobaltates is mapped here with reference to the changed local environment at B-site due to nickel doping. We present here,thetheoretical formulationto calculate the temperature-dependent (1K < T < 1000K) thermal expansion and specific heat of NdCo1-xNixO3 (0.05≤x≤0.5) using modified Rigid Ion Model (RIM) and AIM theory. In addition, the results on the cohesive energy (ϕ) in orthorhombic perovskite phase, bulk modulus (B) and Debye temperature (θD) are also presented.

A new multisensor (i.e. resistive and magnetic) $CrI_{3}$-$WTe_{2}$ heterostructure (HS) to detect the toxic gases $BrF_3$ and $COCl_2$ (Phosgene) has been theoretically studied in our present investigation. The HS has demonstrated sensitivity towards both the gases by varying its electronic and magnetic properties when gas molecule interacts with the HS. Fast recovery time ($< 0.14 fs$) under UV radiation has been observed. We have considered two configurations of $BrF_3$ adsorbed HS; 1) when F ion interacts with HS (C1) and 2) when Br ion interacts with HS (C2). In C1 case the adsorption energy $E_{ad}$ is observed to be -0.66 eV while in C2 it is -0.95 eV. On the other hand in case of $COCl_2$ $E_{ad}$ is found to be -0.42 eV. Magnetic moments of atoms are also found to vary upon gas adsorption indicates the suitability of the HS as a magnetic gas sensor. Our observations suggests the suitability of $CrI_{3}$-$WTe_{2}$ HS to respond detection of the toxic gases like $BrF_3$ and $COCl_2$., 7 pages, 4 figures

We have synthesized a series of Sm 0.55 Sr 0.45−x Ag x MnO 3 (x = 0 & 0.15) by conventional solid state reaction method to scrutinize the effect of monovalent Ag + as a replacement of Sr 2+ ion on structural, electrical, magnetotransport and thermoelectric properties. The structural parameters obtained using Rietveld refinement of X-ray diffraction data which showed perovskite structure having orthorhombic ( Pnma ) symmetry without any detectable impurity phase. It is observed that M ZFC and M FC curves become more manifested as Ag + content is increased which indicates an increase in magnetic frustration arising due to bending of Mn-O-Mn bond. The M-H plots show the narrow hysteresis loops which indicate the soft ferromagnetic nature. Magnetic studies also show that the Curie temperature T C is found to decrease with Ag + content. The metal–insulator transition temperature (T MI ) is observed which decreases with the increase of Ag + content when magnetic field is applied. The resistivity data in high temperature region are explained within the framework of variable range hopping (VRH) and small polaron hopping (SPH) models. The thermoelectric power (S) of the reported samples exhibits a crossover from positive to negative value and value of S increases in doped samples. The analysis of thermoelectric power data confirms that the small polaron hopping model in high temperature region and at low temperature electron–magnon scattering is the dominating in the FM region. With increasing the Ag + content the samples showed very high magneto-resistance (MR%) and temperature coefficient of resistance (TCR%) which make the compound more promising for scientific and technological applications.

Rare-earth cobaltates LaCo 1−x A x CoO 3 (A = Mg, Rh, Ti, Nb and 0.02 ≤ x ≤ 1) have been systematically investigated to elucidate the effect of B site substitution on thermal and elastic properties. Specific heat, thermal expansion coefficient and bulk modulus of rare earth cobaltate LaCoO 3 with Mg, Rh, Ti and Nb in the perovskite structure at B-site has been studied by means of a Modified Rigid Ion Model (MRIM) and AIM theory which has been found to be adequately suitable for such description for the rare earth cobaltates Ln 1−x Sr x CoO 3 (Ln = Pr, Nd, Sm and Dy) materials [J. of Alloys Compd. 661 (2016) 257–267]. The partial replacement of rare earth cation by divalent, trivalent, tetravalent and pentavalent introduces large size and charge mismatch at B-site affecting the bulk modulus and thermal properties. The concentration dependence of the molecular force constant ( f ), Reststrahlen frequency (υ), cohesive energy (ϕ), Debye temperature (θ D ) and Gruneisen parameter (γ) are investigated for the first time. A fairly good agreement has been found between the observed and calculated values of the cohesive energy for these doped compounds. The trend of variation of specific heat, thermal expansion coefficient, Debye temperature with molar volume, temperature and concentration respectively are predicted probably for the first time for the doped rare earth cobaltates.

The perovskite manganites compounds with nominal composition YMn 1-x Ru x O 3 (YMRO) ( x = 0, 0.05, 0.1 and 0.2) were investigated systematically through structural, morphology and thermal transport measurements. Our thermopower and specific heat measurements indicate that the ground state of rare earth manganite compounds is highly sensitive to the ruthenium (Ru) concentration at Mn-site and henceforth to its cationic radius. These properties were analyzed by considering various models and empirical relations. The high value and complicated temperature dependence of thermopower (S) is an indication of electron–magnon scattering in these systems. The observation of giant suppression in the S with increasing Ruthenium content confirms the mixed-valence subsistence of Mn - Ru network. Specific heat measurements depict an anomaly in the vicinity of T N and associated entropy change, was then obtained by subtracting the lattice part from the experimental data, indicating the existence of magnetic ordering and magnetic inhomogeneity in the samples.

Silver ions substituted samarium strontium manganite (Sm0.55Sr0.30Ag0.15MnO3) pervoskite was synthesized by using respective oxides in stoichiometric ratio through solid state reaction. The as-prepared sample was characterized by various analytical techniques to confirm its formation and understand the effect of monovalent silver ions in pervoskite lattice. X-ray diffraction pattern confirms the single phase formation while grain morphology in SEM image indicates good connectivity among the grains. The enhancement in metal to insulator transition temperature shows quenched disorder and magnetoresistance phenomena. The magnetoresistance (MR) and temperature coefficient of resistance (TCR) emerge from grain growth factor and homogeneity induced by Ag+ ions in the lattice. The reduction in hysteresis loss resulted from antiferromagnetic - ferromagnetic (TN) and ferromagnetic - paramagnetic (Tc) transitions reveals the removal of disorder in perovskite lattice by Ag+ ions substitution. This increases the magnetic moment across distinct ions on the applying magnetic field. The rise in MR% (~99%) with silver doping emerging from smooth spin tunneling of the grains across the boundary and suppression of the disordered magnetic fluctuations with increase in magnetic field has been reported. The present compound exhibits the first order nature of magnetism and observed first time the highest value of TCR ~ 95%.

Polycrystalline yttrium barium cobaltite (YBaCo4O7) powdered sample was prepared by conventional solid state reaction route using high purity yttrium oxide, barium carbonate and cobalt oxide. The as-prepared sample was characterized by XRD diffraction, SEM/EDAX, Raman analytical techniques, resistivity and magnetization measurements for structural, morphological, electrical and magnetic properties assessment. XRD pattern confirms the single phase formation of the sample without any impurity. SEM image shows the hexagonal growth of the crystal and EDAX spectrum reveals stoichiometric composition of as prepared sample. The variation in electrical resistivity from 90 K to 300 K follows the variable range hopping conductivity mechanism. The strong broad overlapped Raman peaks of Co–O and Y–O stretching and bending vibrations of tetrahedral CoO4 with included components of YO6 of octahedral symmetry are obtained at 542 cm−1, 486 cm−1 and 636 cm−1, 436 cm−1, respectively. DC magnetic susceptibility exhibits very weak ferromagnetism below 80 K and does not obey Curie-Weiss law.

The polycrystalline samples with nominal composition Eu0.5Sr0.5Mn1−x Cr x O3 (0 ≤ x ≤ 0.1) were prepared by the conventional solid state reaction method and characterized by X-ray diffraction, scanning electron microscopy and electrical resistivity behavior without and with magnetic field. The structural parameters obtained by using Rietveld refinement of X-ray diffraction data showed that all samples crystallize with orthorhombic perovskite type symmetry with Pbnm space group. The scanning electron micrograph images reveal that the increase in Cr substitution hinders grain growth and grain connectivity. The temperature dependence of electrical resistivity show the semiconducting nature of these compounds and support the small polaron hoping model and variable range hopping conduction model. The calculated hopping distance and activation energy decreased as rate of Cr content increased whereas density of states at Fermi level increased. A large negative magnetoresistance is also present in the sample at the lowest temperature of measurements.

We have investigated the thermodynamic properties of Ln1−xSrxCoO3 (Ln = Pr, Nd, Sm, Dy and 0 ≤ x ≤ 1) perovskites using modified rigid ion model (MRIM) and a novel atomistic approach of Atoms in Molecules (AIM) theory. The effect of Sr doping on lattice specific heat and thermal expansion coefficient as a function of temperature (1 K ≤ T ≤ 300 K) are reported probably for the first time. The MRIM results on thermal expansion coefficient of Sr doped LnCoO3 (Ln = Pr, Nd, Sm and Dy) suggest that higher Sr doping may not be applicable to solid oxide fuel cell. Besides, we have reported bulk modulus (B), cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θD), Gruneisen parameter (γ) and specific heat. It is found that the present model has a promise to predict the thermodynamic properties of other perovskites as well.

We have synthesized the single phase polycrystalline sample of silver doped disordered Sm0.55Sr0.45−xAgxMnO3 using the conventional solid state method. They have been investigated by X-ray diffraction for phase evolution and their Rietveld refined X-ray diffraction pattern indicates an increase in lattice parameters and unit cell volume with Ag doping. The magnetization analysis shows the presence of a first order paramagnetic to ferromagnetic transition; the transition temperature and amount of thermal hysteresis decreases on Ag doping. The transport, magneto-transport results indicates decrease in metal to insulator transition, drastic increase in resistance and temperature coefficient of resistance (TCR %) with nearly unaffected colossal magnetoresistance effect which indicates that at least a part of silver is incorporated in the lattice. Scanning electron micrographs indicate that silver has also increased the grain growth sharpness and thus decrease the effect of grain boundary scattering. The significant value of TCR of ∼43% of our samples indicates their applied nature for bolometric application.

The Single phase Ho1-xGdxMnO3 (0 ≤ x ≤ 0.1) compounds were synthesized by solid-state reaction techniques and characterized with various techniques such as X-ray diffraction, scanning electron microscopy, energy dispersive spectroscopy, Raman spectroscopy, ferroelectric loop tracer. The Rietveld refined X-ray diffraction and Raman patterns indicate that all the compounds exhibit a single-phase hexagonal structure with a P63cm space group. The room temperature Raman spectra signify that the phonon peaks observed in all reported samples, slightly shift towards the lower temperatures. Moreover, an increase in the polarization values and reduction of leaky nature with increment in Gd concentration has been observed. The improved ferroelectric parameter obtained in our study is an advancement in the present understanding of multiferroic compounds.

The brownmillerite structure of a technologically important oxide Ca2Fe2O5 (CFO) consists of alternating layers of octahedra and tetrahedra of Fe and O, with the tetrahedral layers having intrinsic O vacancies. In this work, using first principles density functional theory based calculations, we have studied the stability, structure and electronic properties of the polar (0 1 0) surface of CFO. In contrast with those observed in case of the polar surfaces of conventional perovskites, we find that the stoichiometric, unreconstructed, Fe containing terminations are more stable than the non-stoichiometric reconstructed ones. In particular, our calculations show that depending on temperature and oxygen partial pressure, there are two possible stable terminations: (a) the layer containing the Fe and O atoms in the octahedron and (b) the layer containing the Fe and O atoms in the tetrahedron. While the former is metallic, the later has a band gap. The unreconstructed terminations are stabilized by dipole compensation through charge rearrangement in the surface layers during structural relaxations.

In this study, we have employed the first-principles calculations to investigate the influence of various point defects such as vacancy and impurities in SnO monolayer (ML) through the electronic and magnetic properties. Our results demonstrate the magnitude of the formation energy decreases in the order of B > C > N, which may be influenced by the different electronegativities. All these defective systems, defects could induce some defect energy levels in the band gap and significantly enhance the adsorption strength for capture O2 molecule. The analysis of adsorption energy of O2 molecule and electronic properties reveal the strong interaction of free O2 with the defective monolayer. These findings may provide useful information to understand the origin of magnetism in the SnO monolayer in the presence of defects. Moreover, our work may provide a useful way to use of SnO ML as a catalyst in oxygen reduction reaction and gas sensor devices.

In the present study, we select the toxic gases such as NO2, NO, SO2, NH3, CO and CO2 to examine the sensing capacity of S-vacancy SnS monolayer as a gas sensor. The selectivity towards a gas by a sensing device is investigated in terms of adsorption energy, charge transfer and electronic properties of the most stable geometries of the adsorbed system. Comparison of the adsorption behavior of species on the pristine and defective ML, reveals that defective monolayer is more sensitive towards SO2, NO and NO2 molecules with the chemisorption process. The density of states show the adsorption of NO and NO2 significantly modify the electronic properties of the SV-SnS ML, but the strong adsorption creates difficulty in desorption process and shows unrealistic use as a gas sensor at room temperature. At the same time, due to the desirable adsorption energy of SO2 and short recovery time, SV-SnS ML can be a promising gas sensing material for SO2 gas detection. The present findings demonstrate SV-SnS ML, could be used as a potential material for gas absorbent and sensing applications.

We have investigated the lattice distortions due to charge and size mismatch in complex oxides (La, Y)1-x(Te4+, Zr4+)xMnO3and its effect on elastic and thermal properties of these complex perovskite manganites. The revealed data on specific heat, thermal expansion, Debye temperature and Bulk modulus studied as a function of lattice distortions using a novel atomistic approach of Atom in Molecules(AIM) theory and Modified Rigid Ion Model (MRIM) are presented for some concentrations (x) of (La, Y)1-x(Te4+, Zr4+)xMnO3 in a wide temperature range. Studied compounds exhibit anomalous increase in Bulk modulus and Debye temperature with increase in doping concentration of tetravalent Te4+ and Zr4+cations at A-site. These compounds give us an unique opportunity to observe the effect of charge and size variance at A-site in perovskite structure without the effect of JT distortions due to occurrence of these compounds in Rhombohedra and hexagonal symmetry with high variance.

The electronic conduction mechanism in (La0.7Ba0.3MnO3)1-x (BaTiO3)x (x = 0.05) compound have been studied. The structure and phase purity of sample have been characterized using XRD technique. The diffraction pattern is explained on the basis of double phase Rietveld refinement and the calculated structural parameters of both the two phases are determined. It is observed that BaTiO3 significantly shifts the TMI temperature below the room temperature. The conduction mechanism has been analyzed for T

The effects of doping Mo in SrCoO3-δ on the elastic and thermal properties have been studied at temperature 10K≤T≤1000K by using Modified Rigid Ion Model (MRIM). The model has been applied to describe the temperature dependence of specific heat and thermal expansion coefficient. Also, the calculated bulk modulus (B), Reststrahlen frequency (υ), cohesive energy (ϕ), Debye temperature (θD) and Gruneisen parameter (γ) are reported and discussed.

We have performed the density functional theory calculations on heterostructure (HS) of MoS2 and MoB2 monolayers. The aim of this study is to assess the influence of MoB2 on electron transport of adjacent MoS2 layer. In present investigation we predict that the electronic properties of MoS2 monolayer is influenced by 4d-states of Mo in MoB2 monolayer. Whereas, the B atoms of MoB2 and S atoms of MoS2 exhibit overlapping of intermediate atomic orbitals thereby collectively construct the interfacial electronic structure observed to be metallic in nature. From charge density calculations, we have also determine that the charge transfer is taking place at the interface via B-2p and S-3p states. The bonds at the interface are found to be metallic which is also confirmed by adsorption analysis. Thermoelectric performance of this HS is found be in good agreement with available literature. Low Seebeck coefficient and high electrical conductivity further confirms the existence of metallic state of the HS.

We have investigated the bulk modulus and thermal properties of proton conducting perovskite RCeO 3 ( R = Ba, Sr) for the first time by incorporating the effect of lattice distortion in modified rigid ion models (MRIM). The computed bulk modulus, specific heat, thermal expansion coefficient and other thermal properties of BaCeO 3 and SrCeO 3 reproduce well with the available experimental data. In addition the cohesive energy ( ϕ ), molecular force constant ( f ), reststrahlen frequency ( ν ), Debye temperature ( θ D ) and Gruneisen parameter ( γ ) are also reported and discussed. The specific heat results can further be improved by taking into account the spin and the orbital ordering contribution in the specific heat formulae.

We have synthesized Pr0.67Sr0.33−xAgxMnO3 (0 ≤ x ≤ 0.1) compound by conventional solid state reaction method at different sintering temperature. The structural parameters obtained using Rietveld refinement of X-ray diffraction data which showed perovskite structure with orthorhombic (Pnma) symmetry without any detectable impurity phase. The grain growth and grain connectivity extensively improved at higher sintering temperature with doping concentration. Depending upon the doping and the increment of sintering temperature, the samples showed very high magneto-resistance (MR%) and temperature coefficient of resistance (TCR). An improvement in magneto-resistance and TCR with increasing the sintering temperature i.e., 1200–1300 °C which make the compound more promising for scientific and technological applications.

We have investigated the various lattice distortions in complex oxides Ca1-xLaxMnO3 and its effect on elastic and thermal properties of these perovskite manganites, especially Debye temperature of these complex oxides. The revealed data on Bulk modulus and Debye temperature studied as a function of lattice distortions using a novel atomistic approach of Atom in Molecules(AIM) theory and Modified Rigid Ion Model (MRIM) are in closer agreement with the available experimental data for some concentrations (x) of Ca1-xLaxMnO3. We demonstrate that the distortions introduced due to electron concentration, size mismatch and JT effects are the dominant factor, whereas charge mismatch and buckling of Mn-O-Mn angle influence the thermal properties to a lesser degree in the ferromagnetic state.

Ab-initio calculations are carried out to study the electronic and chemical bonding properties of Intermetallic full Heusler compound Pd2HfIn which crystallizes in F-43m structure. All calculations are performed by using density functional theory (DFT) based code Quantum Espresso. Generalized gradient approximations (GGA) of Perdew– Burke– Ernzerhof (PBE) have been adopted for exchange-correlation potential. Calculated electronic band structure reveals the metallic character of the compound. From partial density of states (PDoS), we found the presence of relatively high intensity electronic states of 4d-Pd atom at Fermi level. We have found a pseudo-gap just abouve the Fermi level and N(E) at Fermi level is observed to be 0.8 states/eV, these finding indicates the existence of superconducting character in Pd2HfIn.

A variety of theoretical and experimental works have reported several potential applications of MoS2 monolayer based heterostructures (HSs) such as light emitting diodes, photodetectors and field effect transistors etc. In the present work, we have theoretically performed as a model case study, MoS2 monolayer deposited over insulating SrTiO3 (001) to study the band alignment at TiO2 termination. The interfacial characteristics are found to be highly dependent on the interface termination. With an insulating oxide material, a significant band gap (0.85eV) is found in MoS2/TiO2 interface heterostructure (HS). A unique electronic band profile with an indirect band gap (0.67eV) is observed in MoS2 monolayer when confined in a cubic environment of SrTiO3 (STO). Adsorption analysis showed the chemisorption of MoS2 on the surface of STO substrate with TiO2 termination which is justified by the charge density calculations that shows the existence of covalent bonding at the interface. The fabrication of HS of such materials paves the path for developing the unprecedented 2D materials with exciting properties such as semiconducting devices, thermoelectric and optoelectronic applications.

We have investigated the elastic and thermal properties for Sr1−x A x CoO3 (A=Zn, Ho, and 0≤x≤0.4) probably for the first time, by using the modified rigid ion model (MRIM). The computed elastic constants (C 11, C 12, C 44) are the first report on them. Using these elastic constants, we have computed other related elastic properties like the Bulk modulus (B), Young’s modulus (Y), Shear modulus (G), Poisson’s ratio (σ), Lame’s parameter (μ, λ), transverse, longitudinal and average wave velocity (υ t, υ l, υ m) and Anisotropy parameter (A). Furthermore, by the elastic stability criteria, we predict that Sr1−x A x CoO3 (A=Zn, Ho, and 0≤x≤0.4) are mechanically stable and belongs to metallically bonding materials. Moreover, the thermodynamic properties such as the thermal expansion coefficient (α), cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ D), and Gruneisen parameter (γ) have also been predicted. Besides, the variations of specific heat with temperature are reported for a wide range. To our knowledge, some of the properties are being reported for the first report on these materials.

A theoretical study of electronic and optical properties of metal-halide cubic perovskite, $$\hbox {CsPbI}_3$$ , is presented, using first-principles calculations with plane-wave pseudopotential method as implemented in the PWSCF code. In this approach, local density approximation (LDA) is used for exchange-correlation potential. A strong ionic bonding is observed between Cs and I orbitals and a weak covalent bonding is found between Pb-I and Cs-Pb orbitals. The optical properties of this compound are interesting and it has many applications in optoelectronic devices.

We report that the polycrystalline hexagonal YMn0.9Ru0.1O3 compound can be synthesized by using conventional solid state reaction method at a sintering temperature of 128000. The reflections/diffraction peaks observed in the XRD measurements matched exactly with standard (JCPDS) data for the hexagonal crystal structure of YMnO3 without any extra peaks due to impurities. The dc electrical measurements of the as prepared YMn0.9Ru0.1O3 compound have been carried out below room temperature down to the minimum possible. The electrical measurement of the Ru doped YMnO3 compounds reveal that the resistivity is suppressed with the addition of the ruthenium content and a consistent increase in the resistivity have been witnessed with decreasing temperature. In generalized sense the observed resistivity versus temperature behavior in the studied compounds suggests the induction semiconductor-like character in the material.KeywordsXRD, Electrical resistivity, Manganites

We have investigated the bulk modulus and thermal properties of La1-xSmxCoO3 (0≤x≤0.2) at temperatures 1 K≤T≤300 K probably for the first time by incorporating the effect of lattice distortions using the modified rigid ion model (MRIM). The calculated specific heat, thermal expansion, bulk modulus, and other thermal properties reproduce well with the available experimental data, implying that MRIM represents properly the nature of the pure and doped cobaltate. The specific heats are found to increase with temperature and decrease with concentration (x) for the present. The increase in Debye temperature (θD) indicates an anomalous softening of the lattice specific heat because increase in T3-term in the specific heat occurs with the decrease of concentration (x).

We have investigated the elastic and thermal properties of Sr1-xCdxCoO3 (0=x=0.1) probably for the first time by means of modified rigid ion model (MRIM). In this paper, we present the second order elastic constants (SOECs) and other elastic properties like Bulk modulus (B), Young's modulus (Y), Shear modulus (G), ̠̹̿̓̓̿̾˷̓˰̱̹͂̈́̿˰˸σ˹˼˰̵̜̱̽˷̓˰̵̵̱̱̀͂̽̈́͂˰˸m, l), transverse, longitudinal, ˰̵̷̵̱̱͆͂˰̵͇̱͆˰̵̼̳̹͉͆̿̈́˰˰˸υt, υl˼˰υm) and Anisotropy parameter (A). Here, the SOECs for Sr1-xCdxCoO3 compounds are positive and satisfy the generalized criteria for mechanically stable crystals: (C11-C12) > 0, (C11+2C12) > 0 and C44 > 0 which confirm that Sr1-xCdxCoO3 (0=x=0.1) belong to metallically bonding materials.

In the present decade, considerable interest has been taken in the investigation of anharmonic properties of materials of various kinds [1, 2]. Many workers have contributed in the field through their experimental and theoretical approach. Several efforts have been made in the study of physical and anharmonic properties of solids of different types [3–6]. Utilizing different physical conditions and using several techniques. Some interesting results have been presented by several investigators while studying the anharmonic properties of the substances possessing various crystal structures. Some have studied temperature variation of anharmonic properties of mixed alkali halides and cyanides of rare gas materials [7] of alkali halides [8–10] using ultrasonic [11, 12] and Brillouin scattering [13] methods. The static and Dynamic structural properties of solid C60 are currently the subject of numerous investigations. At room temperature, the crystal has a face-centered cubic fcc structure, the fcc phase has the symmetry of the space group Fm3m with a lattice constant of a0=14.2 A where the C60 molecules rotate freely. With decreasing temperature, the rotational degrees of freedom of the C60 molecules becomes more and more hindered and the solid C60 undergoes a first order structural phase transition from orientationally disordered fcc phase to an orientationally ordered simple cubic structures with four molecules per unit cell located on four different cubic sub lattices having different orientations[14]. Since the discovery of superconducting properties of C60 and the ability to prepare large quantities of this material [15, 16] an enormous amount of work has been carried out on it. Since Krastchmer et al. [14] produced macroscopic quantities of fullerene, knowledge of the molecular and solid state chemistry

We have synthesized and investigated the effect of Ag doping in Pr0.67Sr1−xAgxMnO3 (0≤x≤0.3) perovskite materials via solid state reaction route. The structural, transport and magnetoresistance behavior have been studied. The Rietveld refinement of X-ray diffraction data shows that the compounds crystallize in an orthorhombic structure with Pnma space group with systematic non-linear variation in unit cell volume and lattice parameters. The grain morphology confirms that silver enhances conducting channels and reacts well with the compound only upto a certain doping level. The temperature dependent zero-field and in-field resistivity have been measured between 5 K and 300 K. The samples exhibit a systematic variation in metal to insulator transition temperature and a large magnetoresistance at x=0.10. The highest value of temperature coefficient of resistance has been observed by us for the first time. The results revealed that Ag takes part in the reaction only when the doping amount is small and at higher doping the system becomes a two phase composite.

The elastic and thermal properties of highly Sr-doped Ln0.05Sr0.95CoO3−δ (Ln = Sm, Gd, Dy, Y, Ho, Er, Tm and Yb) in cubic phase have been investigated probably for the first time by using modified rigid ion model (MRIM). The computed results on the second order elastic constants (C11, C12 and C44) and their combinations are reported and discussed. The calculated elastic constants indicated that Ln0.05Sr0.95CoO3−δ are mechanically stable. Besides, we have reported the cohesive, thermal properties and the variations of specific heat with temperature are discussed in detail.

We have investigated the structural and magnetic properties of strontium (Sr2+) substituted polycrystalline doubly-ordered perovskite Y2−xSrxNiMnO6 (x = 0, 0.05, 0.1), characterized with X-ray diffraction, X-ray photoelectron spectroscopy, dc-magnetization, and frequency-dependent linear ac-susceptibility measurements. The undoped Y2NiMnO6 is observed with traces of YMnO3 and NiO as secondary phases, whereas the phase purity improved with Sr2+ substitution. The XRD patterns of Y2−xSrxNiMnO6 (x = 0, 0.05, 0.1) are fitted with the Rietveld refinement in a monoclinic (P21/n) space-group symmetry and the secondary phases YMnO3 and NiO are fitted in hexagonal (P63cm) and cubic (Fm3m) space groups, respectively. The structural modifications observed with Sr2+ substitution manifest in octahedral distortion, altered lattice parameters, average bond-length, bond angles, tolerance factor, and corresponding electron bandwidths. The XPS study confirms the presence of Jahn-Teller (JT-active) species (Ni3+, Mn3+) along with Ni2+, Mn4+ ions. Increasing Sr2+ concentration triggers the paramagnetic (PM) to ferromagnetic (FM) transition spontaneously, along with increased transition temperature (Tc). The thermomagnetic study in field cooled/zero-field cooled modes and linear ac-susceptibility measurements suggest that the investigated compounds exhibit nonspontaneous and cumulative magnetic domain-wall dynamics to attain FM-state with glassy-type behavior toward lower temperatures.

We have investigated the specific heat, thermal expansion and thermodynamic properties of BaRuO3 in rhombohedral, hexagonal and cubic phase using the modified rigid ion model (MRIM) by incorporating the effect of lattice distortions. The calculated Debye temperature, specific heat and other thermal properties reproduce well with the available experimental data, implying that MRIM represents properly the nature of the perovskite-type BaRuO3. Besides, we have reported the thermal expansion (α), bulk modulus (B), cohesive energy (ϕ), molecular force constant (f), Reststrahlen frequency (υ), Debye temperature (θ D), and Gruneisen parameter (γ).

We have investigated the specific heat of hole-doped vanadium oxides Y 1− x Ca x VO 3 (0 ≤ x ≤ 0.11), Pr 1− x Ca x VO 3 (0 ≤ x ≤ 0.3) and Nd 1− x Sr x VO 3 (0 ≤ x ≤ 0.2) probably for the first time by applying the Modified Rigid ion model (MRIM). The results obtained on temperature dependent (1 K ≤ T ≤ 300 K) specific heat are in reasonably good agreement with the experimental data. The impact of lattice distortions on the elastic and thermal properties of the present Mott insulators is portrayed by an atomistic approach. The scope of further improvement in the present model has also been discussed.

We present the effect of A-site double doping (La0.254Y0.746) on elastic and thermal properties of EuVO3 in a wide doping range (0≤x≤1), using a modified rigid ion model (MRIM). Various lattice distortions and their relation to bulk modulus has been investigated systematically. The effect of the lattice distortions on thermodynamic properties of Eu1−x (La0.25Y0.74) x VO3 has been explored by an atomistic approach. The computed results emphasize that the Debye temperature decreases while the specific heat increases with increase in doping concentration (x). The computed temperature dependent (1 K≤T≤300 K) specific heat trends are in accordance with the corresponding experimental data at various compositions. Future scope of MRIM has also been discussed.