[en] Highlights: • The strained induced electronic and transport properties of Half-Heusler TaIrGe compound have been reported. • The energy bandgap increases/decreases via increasing tensile/compressive strain. • Obtained low value of lattice thermal conductivity (k_l) and high value of power factor govern enhanced TE performance of TaIrGe compound. • Enhanced figure of merit (ZT)~0.82 for TaIrGe at T = 1200 K under 4% tensile strain is found. The structural, electronic and transport properties of the Half-Heusler TaIrGe compound have been reported at different values of tensile and compressive strain using density functional theory (DFT) in conjunction with Boltzmann transport theory. The mechanical and thermodynamical stability of TaIrGe at different values of isotropic strain is confirmed by the calculated value of elastic constants and the phonon dispersion curve, respectively. The electronic structure calculations reveals that the energy bandgap changes significantly on applying tensile and compressive strain. The calculated low value of lattice thermal conductivity (k_l) and high value of power factor are key factors in enhancing the performance of resultant thermoelectric material. The calculated value of figure of merit (ZT) for pristine TaIrGe compound is 0.69 and it attains a maximum value (0.82) for 4% tensile strain at T​=​1200​K, which shows that it can be used as an efficient thermoelectric material under the effect of isotropic strain for high temperature applications.

[en] The dynamical effect of wall-fluid interaction on diffusion in direction perpendicular to confining walls has been studied, theoretically. The properties of fluids which incorporates the effect of static changes in confined fluid has been modified to include, directly, the dynamical effects of wall on the motion of particles. The results obtained for VACF in perpendicular direction of channel of width of two atomic diameters are presented and compared with the molecular dynamic (MD) simulation results as well as the results obtained without including the dynamical effect.

[en] First three non-vanishing sum rules for the bulk and longitudinal stress auto-correlation functions have been evaluated for liquid Rb at six thermodynamic states along the liquid-vapour coexistence curve. The Mori memory function formalism and the frequency sum rules have been used to calculate bulk and longitudinal viscosities. The results thus obtained for the ratio of bulk viscosity to shear viscosity have been compared with experimental and other theoretical predictions wherever available. The values of the bulk viscosity have been found to be more than the corresponding values of the shear viscosity for all six thermodynamic states investigated here

[en] The dynamics of fluid confined in a nano-channel with smooth walls have been studied through velocity autocorrelation function within the memory function approach by incorporating the atomic level interactions of fluid with the confining wall. Expressions for the second and fourth sum rules of velocity autocorrelation have been derived for nano-channel which involves fluid-fluid and fluid-wall interactions. These expressions, in addition, involve pair correlation function and density profiles. The numerical contributions of fluid-wall interaction to sum rules are found to play a very significant role, specifically at smaller channel width. Results obtained for velocity autocorrelation and self-diffusion coefficient of a fluid confined to different widths of the nanochannel have been compared with the computer simulation results. The comparison shows a good agreement except when the width of the channel is of the order of two atomic diameters, where it becomes difficult to estimate sum rules involving the triplet correlation’s contribution

[en] Graphene-like two-dimensional (2D) monolayer structures GaN has gained enormous amount of interest due to high thermal stability and inherent energy band gap for practical applications. First principles calculations are performed to investigate the electronic structure and strain-mediated electronic properties of pristine and Mn-doped GaN monolayer. Binding energy of Mn dopant at various adsorption site is found to be nearly same indicating these sites to be equally favorable for adsorption of foreign atom. Depending on the adsorption site, GaN monolayer can act as p-type or n-type magnetic semiconductor. The tensile strength of both pristine and doped GaN monolayer (∼24 GPa) at ultimate tensile strain of 34% is comparable with the tensile strength of graphene. The in-plane biaxial strain modulate the energy band gap of both pristine and doped-monolayer from direct to indirect gap semiconductor and finally retendered theme into metal at critical value of applied strain. These characteristics make GaN monolayer to be potential candidate for the future applications in tunable optoelectronics. (paper)

[en] Confining walls of nano channel are taken to be elastic to study their effect on the diffusion coefficient of fluid flowing through the channel. The wall is elastic to the extent that it responses to molecular pressure exerted by fluid. The model to study diffusion is based on microscopic considerations. Results obtained for fluid confining to 20 atomic diameter width contrasted with results obtained by considering rigid and smooth wall. The effect of roughness of wall on diffusion can be compensated by the elastic property of wall

[en] A dynamical model is proposed to study the effect of confinement down to nano-dimension on the self-diffusion coefficient. The model is built on the consideration that the confinement affects molecular motion. The model introduces the concept of a microscopic (local) self-diffusion coefficient which varies as a function of distance from the walls of the channel. As one moves towards the confining walls the self-diffusion coefficient decreases, affecting the fluidity of the fluid in a nano-channel. The macroscopic self-diffusion coefficient has also been found to be affected by the microscale/nanoscale confinement. The effect of confinement has been found to be more on denser fluid than on a dilute fluid. The denser fluid provides an additional artificial wall which further restricts the flow of fluid. The relevance of this work to the study of flow of fluid, like blood in arteries, has also been discussed

[en] The sol-gel system which is known, experimentally, to exhibit a power law decay of stress autocorrelation function has been studied theoretically. A second-order nonlinear differential equation obtained from Mori's integro-differential equation is derived which provides the algebraic decay of a time correlation function. Involved parameters in the expression obtained are related to exact properties of the corresponding correlation function. The algebraic model has been applied to Lennard-Jones and sol-gel systems. The model shows the behaviour of viscosity as has been observed in computer simulation and theoretical studies. The expression obtained for the viscosity predicts a logarithmic divergence at a critical value of the parameter in agreement with the prediction of other theories.

[en] A model has been proposed wherein self consistent phonon theory together with the thermodynamic perturbation theory is employed to determine a trial Hamiltonian is employed to determine thermodynamic parameters based on pining as well as nearest neighbor quadratic-quartic interactions.

[en] Hidden Markov Model (HMM) has been developed for avalanche warning on 10 different road sectors in Pir-Panjal and Great Himalayan mountain ranges of North-West Himalaya. The model uses a data set of nine snow and meteorological variables—average air temperature, snow temperature index, snow drift index, snowfall in 24 h, snowfall in 48 h, snow water equivalent, snowfall intensity, standing snow and snowpack settlement collected during past 20 winters (1992–2012). The HMM is composed of four observations derived from the model input variables and four state variables. The state variables of the model are four levels of avalanche danger (No, Low, Medium and High). Single HMM has been developed to provide avalanche warning for both direct and delayed/wet avalanches with a lead time of two days. The HMM has been validated with (Case-1) and without (Case-2) incorporating delayed/wet avalanches using data collected during four winters (2012–2016) and compared with official Avalanche Warning Bulletin issued by Snow and Avalanche Study Establishment during these winters. The model has been validated through computation of accuracy measures such as percent correct (PC), bias, false alarm rate, probability of detection and Heidke Skill Score. The PC of the HMM for different stations for Case-1 varies from 80.1 to 98.6% for day-1 and 81.2 to 98.3% for day-2 and that for Case-2 from 82.2 to 98.6% for day-1 and 83.3 to 98.3% for day-2.