Pachhunga University College

Aizawl, India

Pachhunga University College

Aizawl, India
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Sandeep,Mizoram University | Rai D.P.,Pachhunga University College | Shankar A.,North Bengal University | Ghimire M.P.,Mizoram University | Thapa R.K.,Mizoram University
Journal of Physics: Conference Series | Year: 2016

Samarium doping effects on the thermoelectric properties in Eu1-xSmxAlO3 (x=0%, 50%, and 100%) were studied using first principles calculations based thermal transport property measurement. The result indicate that the compound is an intrinsic n-type material. Samarium doping has a positive effect on the overall thermoelectric performance of the Eu1-xSmxAlO3 system, with sharp increase in figure of merit (ZT) observed when x=0, 50 and 100% up to 150K. Compared to x=0 and 100%, the case of x=50% was found to have more positive increment in ZT value suggesting that the doing to have positive effect on figure of merit in Eu1-xSmxAlO3. Furthermore, all the samples show stable thermoelectric compatibility factors over a broad temperature range from 700 to 1000 K, which could have great benefits for their practical applications. It is concluded that the overall thermoelectric performance of the Eu1-xSmxAlO3 could be highly enhanced using doping techniques.


Sandeep,Mizoram University | Rai D.P.,Pachhunga University College | Shankar A.,North Bengal University | Ghimire M.P.,Condensed Matter Physics Research Center | Thapa R.K.,Mizoram University
Journal of Physics: Conference Series | Year: 2016

Gadolinium doping effects on the thermoelectric properties in Sm1-xGdxAlO3 (x=0%, 50%, and 100%) were studied using first-principles calculations based thermal transport property measurement. The result indicates that the compound is an intrinsic n-type material. Samarium doping has a positive effect on the overall thermoelectric performance of the Sm1- xGdxAlO3 system, with a sharp increase in the figure of merit (ZT) observed when x=0, 25, 50, 75 and 100% up to 800K. Compared to x=0 and 100%, the case of x=50% was found to have a more positive increment in ZT value suggesting that the doping to have a positive effect on the figure of merit in Sm1-xGdxAlO3. Furthermore, all the samples show stable thermoelectric compatibility factors over a broad temperature range from 700 to 1000 K, which could have great benefits for their practical applications. It is concluded that the overall thermoelectric performance of the Sm1-xGdxAlO3 could be highly enhanced using doping techniques. © Published under licence by IOP Publishing Ltd.


Joshi H.,Mizoram University | Rai D.P.,Pachhunga University College | Verma K.D.,P.A. College | Bhamu K.C.,Goa University | Thapa R.K.,Mizoram University
Journal of Alloys and Compounds | Year: 2017

We have presented the electronic and thermoelectric properties of d2/do type Heusler compounds TiXSb (X = Ge, Si) using Full Potential Linearized Augmented Plane Wave method (FP-LAPW), based on Density Functional Theory (DFT). For electron exchange, we have considered the most common Generalized Gradient Approximation (GGA), exchange potential. The electronic structure of both TiGeSb and TiSiSb showed overlapping between the valance and the conduction band, indicating their metallic nature. The transport coefficients were calculated by a post DFT treatment which involves the semi-classical Boltzmann Theory as implemented in the code BoltzTraP. The thermoelectric parameters are calculated along perpendicular and parallel directions with respect to chemical potential (μ) and temperature. Furthermore, we have also considered the phononic contribution to thermal conductivity (κp) for better understanding of the materials thermodynamics and efficiency (ZT). The calculated ZT values showed TiSiSb as potential thermoelectric candidate at room temperature and under normal conditions, whereas TiGeSb had poor thermoelectric properties. © 2017 Elsevier B.V.


Kaur K.,Panjab University | Rai D.P.,Pachhunga University College | Thapa R.K.,Mizoram University | Srivastava S.,Panjab University
Journal of Applied Physics | Year: 2017

We explore the structural, electronic, mechanical, and thermoelectric properties of a new half Heusler compound HfPtPb, an all metallic heavy element, recently proposed to be stable [Gautier et al., Nat. Chem. 7, 308 (2015)]. In this work, we employ density functional theory and semi-classical Boltzmann transport equations with constant relaxation time approximation. The mechanical properties, such as shear modulus, Young's modulus, elastic constants, Poisson's ratio, and shear anisotropy factor, have been investigated. The elastic and phonon properties reveal that this compound is mechanically and dynamically stable. Pugh's ratio and Frantsevich's ratio demonstrate its ductile behavior, and the shear anisotropic factor reveals the anisotropic nature of HfPtPb. The band structure predicts this compound to be a semiconductor with a band gap of 0.86 eV. The thermoelectric transport parameters, such as Seebeck coefficient, electrical conductivity, electronic thermal conductivity, and lattice thermal conductivity, have been calculated as a function of temperature. The highest value of Seebeck coefficient is obtained for n-type doping at an optimal carrier concentration of 1.0 × 1020 e/cm3. We predict the maximum value of figure of merit (0.25) at 1000 K. Our investigation suggests that this material is an n-type semiconductor. © 2017 Author(s).


Lalramliana,North - Eastern Hill University | Lalramliana,Pachhunga University College | Yadav A.K.,North - Eastern Hill University
Journal of Parasitic Diseases | Year: 2016

Three locally isolated strains of entomopathogenic nematodes (EPNs), viz. Heterorhabditis indica, Steinernema thermophilum and Steinernema glaseri, from Meghalaya, India were characterized in terms of storage temperature and survival and infectivity of their infective juveniles (IJs). The survival and infectivity of nematode IJs was studied at, 5 ± 2 and 25 ± 2 °C, for a period of 120 days, using deionized water as storage medium. The viability of nematode IJs was checked by mobility criterion at different storage periods, while the infectivity of nematode IJs was ascertained on the basis of establishment of IJs, using Galleria mellonella larva mortality tests in petridishes. The results of this study revealed that storage temperature markedly affects the survival as well as the establishment of nematode IJs of the three EPN species. At 5 °C, comparatively higher rate of IJ’s survival (i.e. 74–86 %) was observed for 15 days of storage, but the same reduced drastically to 28–32 % after 30 days of storage for H. indica and S. thermophilum. On the other hand, at 25 °C, the survival of nematode IJs was observed till 120 days for all the three studied EPNs. In case of S. thermophilum and S. glaseri, higher rate of IJs survival (>75 %) was observed respectively at 15 and 30 days of observation. The study also showed that the establishment of IJs of the three EPN species declines with increase in storage periods, at both the test temperatures. In general, the nematodes stored at 25 °C showed comparatively better establishment than those stored at 5 °C. Among the three EPN studied, the establishment of S. glaseri was comparatively better than the rest of the species at both the temperatures and for different storage durations. In conclusion, our study adds further valuable information about the effect of storage temperature on survival and infectivity of three indigenous EPN species of Meghalaya, India which appears to be promising biocontrol agents of local insect pests. © 2015, Indian Society for Parasitology.


Ghimire M.P.,Nepal Academy of Science and Technology | Ghimire M.P.,Japan International Center for Materials Nanoarchitectonics | Thapa R.K.,Mizoram University | Rai D.P.,Pachhunga University College | And 3 more authors.
Journal of Applied Physics | Year: 2015

First-principles density functional theory (DFT) is used to investigate the electronic and magnetic properties of Sr4Rh3O10, a member of the Ruddlesden-Popper series. Based on the DFT calculations taking into account the co-operative effect of Coulomb interaction (U) and spin-orbit couplings (SOC), Sr4Rh3O10 is found to be a half metallic ferromagnet (HMF) with total magnetic moment μtot=12μB per unit cell. The material has almost 100% spin-polarization at the Fermi level despite of sizable SOC. Replacement of Rh atom by the isovalent Co atom is considered. Upon full-replacement of Co, a low-spin to intermediate spin transition happens resulting in a HMF state with the total magnetic moment three-time larger (i.e., μtot=36μB per unit cell), compared to Sr4Rh3O10. We propose Sr4Rh3O10 and Sr4Co3O10 as candidates of half metals. © 2015 AIP Publishing LLC.


Sandeep,Mizoram University | Rai D.P.,Pachhunga University College | Rai D.P.,Beijing Computational Science Research Center | Shankar A.,Mizoram University | And 3 more authors.
Physica Scripta | Year: 2015

The electronic and magnetic properties of EuAlO3 are calculated by first-principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). The exchange and correlation potential is treated with different approximations: mBJ and GGA + U. Coulomb repulsion (U) has been calculated using super-cell calculations for EuAlO3. The GGA + U calculations reveal an indirect band gap of 4.6 eV for EuAlO3 in the spin down channel supporting the half metallic (HM) nature of the system. An effective integral magnetic moment also supported the HM nature of EuAlO3. © 2015 The Royal Swedish Academy of Sciences.


Mishra R.K.,Mizoram University | Lalneihpuii R.,Mizoram University | Pathak R.,Pachhunga University College
Chemical Physics | Year: 2015

Abstract In the present paper surface tension, Debye temperature, coordination numbers along with microscopic correlations of ten liquid metals are determined using square-well model of correlation functions. Wertheim's solution of the fundamental statistical mechanical equation given by Percus and Yevick for hard spheres is invoked with a square well attractive part as a perturbation tail to get exact solution of the direct correlation function, C(k) in momentum space and the analytical expressions are obtained for structure factor, S(k). These expressions are then used to predict static structure factors for ten liquid metals, leading to fair agreement with experimental data. Radial distribution function g(r) is obtained by Fourier analysis of computed S(k), from which the coordination numbers and the nearest neighbor distances of liquid metals are evaluated. Computed coordination numbers and surface properties of liquid metals using such a simple technique are in good agreement with experimental results. © 2015 Published by Elsevier B.V.


Rai D.P.,Pachhunga University College | Shankar A.,Mizoram University | Sandeep,Mizoram University | Ghimire M.P.,Condensed Matter Physics Research Center | And 3 more authors.
RSC Advances | Year: 2015

A density functional theory (DFT) approach employing generalized gradient approximation (GGA) and the modified Becke Johnson (TB-mBJ) potential has been used to study the electronic and thermoelectric (TE) properties of ZrxHf1-x-yTayNiSn. The presence of an indirect band gap at EF in the parent compound predicts this material to be a small band gap insulator. The substitution of Ta atoms at the Hf site increases the density of states (DOS) at EF which facilitates charge carrier mobility. The influence of Ta content increases the Seebeck coefficient and electrical conductivity, and suppresses the thermal conductivity; as a result the figure of merit ZT is enhanced. We report an increment in ZT value of 36% over the undoped system. The theoretical data were compared with the experimental results. © The Royal Society of Chemistry.


Shankar A.,Mizoram University | Rai D.P.,Pachhunga University College | Chettri S.,Mizoram University | Khenata R.,University of Mascara | Thapa R.K.,Mizoram University
Journal of Solid State Chemistry | Year: 2016

We have investigated the electronic structure, elastic and thermoelectric properties of the filled skutterudite CeRu4Sb12 using the density functional theory (DFT). The full potential linearized augmented plane wave (FP-LAPW) method within a framework of the generalized gradient approximation (GGA) approach is used to perform the calculations presented here. The electronic structure calculation suggests an indirect band gap semiconducting nature of the material with energy band gap of 0.08 eV. The analysis of the elastic constants at relaxed positions reveals the ductile nature of the sample material with covalent contribution in the inter-atomic bonding. The narrow band gap semiconducting nature with high value of Seebeck coefficient suggests the possibility of the thermoelectric application of the material. The analysis of the thermal transport properties confirms the result obtained from the energy band structure of the material with high thermopower and dimensionless figure of merit 0.19 at room temperature. © 2016 Elsevier Inc.

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