ABSTRACT Using a thermodynamic model developed by us to study the structural and electro-optical properties of phase, we investigate the temperature dependence of helical pitch, tilt angle and spontaneous polarization of a homologous series of fluorinated biphenyl benzoate esters (3FnHBM6, n = 2, 5, 7) and one of the series W-316-3 obtained from the mixture of two chiral liquid crystalline compounds 6F2OBi and 3F6HBM6. The free-energy density of the system exhibiting phase is written as an expansion series in terms of all the relevant degrees of freedom: , ψ, P, q and the resulting coupling terms between these order parameters. The values of Landau coefficients are determined from the experimental data of antiferroelectric mesogens 3FnHBM6 (n = 2, 5, 7) and W-316-3 in the phase. Using these coefficients, the electro-optical and structural properties have been studied. We have found good agreements between the theoretical and experimental results.

ABSTRACT A systematic study of a binary system composed of 4-n-pentyl 4′-cyanobiphenyl (5CB) and 4-n-pentyl phenyl 4-n′-hexyloxy benzoate (ME6O.5) mesogens showing an induced smectic A at different molar concentrations has been done. Heat capacity and optical birefringence measurements have been performed around the N-SmA phase transition region. The heat capacity peaks could be fitted well below the N-SmA transition by means of an extended Landau mean-field model. The first-order nature of the transition throughout the composition range can be inferred. This transition is rather close to the tricritical point when the nematic range is sufficiently increased. The latent heat decreases with the increase in the nematic range. For large nematic range, the latent heat drops to zero and the heat capacity peak associated with N-SmA phase transition disappear, contrary to previously reported most of the usual N-SmA phase transition. Precision birefringence measurements also agree well with the heat capacity data.

ABSTRACT Chalcogenide glasses are unquestionably one of the most popular materials known for their phase change property. Phase change materials (PCM) have a key role in the field of photonics, memory devices, imaging, etc. With an aim to study the worth of ternary Sb 10 Se 90-x Gex (x = 0, 19, 21, 23, 25, 27) and quaternary Sb 10 Se 65 Ge 25-y Iny (y = 0, 3, 6, 9, 12, 15) chalcogenide systems as PCM, the composition variation and effect of dopants on the thermal properties of two systems has been probed. The thermal stability of two glass systems has been investigated using criteria such as the S parameter, fragility index, and rate constants at glass transition and crystallization temperatures. The mechanism of the phase change phenomenon occurring in the glasses has been studied using the Avrami index.

ABSTRACT A model combining with Flory-Huggins theory of isotropic mixing and Landau theory is developed to describe the effect of graphene nanoparticles on the isotropic to nematic phase transition. The temperature and concentration of graphene nanoparticles dependence on the orientational order parameter, transition temperature and thermodynamic quantities near the isotropic to nematic phase transition are discussed. The orientational order parameter, transition temperature and enthalpy near the isotropic to nematic phase transition increase with the increase of graphene nanoparticles.

ABSTRACT Barium titanate doped yttrium ceramics with different grain sizes were prepared by a solid-state method at three different sintering temperatures. The SEM micrograph observation revealed well-developed grain morphology and a dense, homogeneous microstructure in the Ba0.98Y0.02Ti0.995O3 ceramics. However, an increase in pores was observed at 1300 °C, affecting the dielectric characteristics. Additionally, at 1350 °C, there was a significant increase in the average grain size to approximately 3.508 µm. The permittivity and conductivity were found to be strongly dependent on the grain sizes; They increased with increasing the grain size down to 1.530 μm on average and then decreased. The grain size-dependent conductivity might be explained by the effect of grain boundary on charge carrier transport. The grain size of the ceramics with the highest permittivity of 1700 was approximately 1.530 μm.

ABSTRACT In the present work, we report the experimental and computational investigations of 3-Hydroxy-4-nitrobenzaldehyde (3H4NB) were examined. Comparing observed and simulated vibrational spectra allowed for the identification of characteristic frequencies and the attribution of band names. For the density functional theory (DFT) calculations, the LSDA functional with 6-311 + G(d,p) degree of approximation was used. Furthermore, the same level of theory was used to calculate molecular orbitals such as natural bond orbitals (NBOs) and the HOMO–LUMO energy gap. The condensed Fukui function and the molecular electrostatic potential (MEP) surface were used to determine the relative electrophilicity and nucleophilicity of the current molecule. Intermolecular hydrogen bonding interactions are studied using Hirshfeld surface analysis and fingerprint plots. Molecular docking analysis was used to investigate the compound's biological activities. The hydrogen bond active binding residues and binding energy of a chosen chemical with carcinogenic activity targets were examined.

ABSTRACT This study examines the electric field-induced orientational instability of the director in a homeotropically oriented nematic liquid crystal (NLC) cell. Transitions from homogeneous homeotropic state to non-homogeneous state and from non-homogeneous to homogeneous planar state were investigated. These transitions have a threshold and may exhibit hysteresis. Threshold voltages for these transitions were calculated and regions of existence of hysteresis were determined depending on the cell parameters. Increasing anchoring energy narrows hysteresis range for homeotropic to non-homogeneous transition and expands it for planar to non-homogeneous transition. The impact of the external electric field on the conditions and parameters of surface plasmon polariton (SPP) propagation in the Au–polymer film–NLC system was theoretically investigated. The effective refractive index of the SPP was found to increase with increasing anchoring energy of the NLC with the polymer film and with decreasing wavelength and applied voltage.

ABSTRACT The three-dimensional anisotropic classical XY ferromagnet has been investigated by extensive Monte Carlo simulation using the Metropolis single spin flip algorithm. The magnetisation (M) and the susceptibility (χ) are measured and studied as functions of the temperature of the system. For constant anisotropy, the ferro-para phase transition has been found to take place at a higher temperature than that observed in the isotropic case. The system gets ordered at higher temperatures for higher values of the strength of anisotropy. The opposite scenario is observed in the case of random anisotropy. For all three different kinds of statistical distributions (uniform, Gaussian, and bimodal) of random anisotropy, the system gets ordered at lower temperatures for higher values of the width of the distribution of anisotropy. We have provided the phase boundaries in the case of random anisotropy. The critical exponents for the scaling laws and are estimated through the finite size analysis.

ABSTRACT Lead-free Sr0.6Ca0.4TiO3 ceramic was prepared by solid-state reaction route. X-ray diffraction technique showed the phase purity and identified the orthorhombic perovskite structure. Scanning Electronic Microscopy observation evidenced homogeneous morphology and dense microstructure. Electrical conduction and dielectric relaxation mechanisms at high temperature have been studied by complex impedance measurement techniques over a wide range of frequencies and temperatures, from 100 Hz to 1 MHz and from 573 K to 783 K. Fitting of impedance measurements allowed us to study grains and grain boundaries electrical characteristics and their contribution to the conduction and dielectric relaxation processes in the ceramic. Electrical conduction in grains is due to oxygen vacancy jumps for temperatures below 733 K and to polarons above 763 K. Electrical DC conductivity in grains and grain boundaries is mainly due to oxygen vacancies. Impedance measurements and relaxation time distribution function calculations show non-Debye-type relaxation effects for both grains and grain boundaries.

ABSTRACT InSe is a III-VI semiconducting layered compound having potential applications in memories, solar cells, infrared sensors, switching devices and optical fibers. In this article various physical parameters of In0.1Se0.9-x Sb x (x = 0, 0.04, 0.08, 0.12) chalcogenide alloy depending on the varying composition of Se and Sb are discussed. The physical parameters include the theoretical calculations of average coordination number, number of constraints, floppy modes, number of lone pair electrons, deviation of stoichiometry, average heat of atomization, mean bond energy, density, molar volume, compactness, cohesive energy, electronegativity, energy band gap, conduction and valance band energy and glass transition temperature. The number of lone pair electrons and floppy modes is found to decrease, whereas the average coordination number, mean bond energy, average heat of atomization and density are found to increase with increasing Sb content. The theoretical values of glass transition temperature are calculated using the Tichy-Ticha and Lankhorst approach.