Pachhunga University College

Aizawl, India

Pachhunga University College

Aizawl, India

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Shankar A.,Mizoram University | Rai D.P.,Pachhunga University College | Rai D.P.,Beijing Computational Science Research Center | Khenata R.,University of Mascara | Thapa R.K.,Mizoram University
Phase Transitions | Year: 2015

The elastic, electronic, magnetic and optical properties of filled skutterudite ROs4P12 (R = Sm, Eu and Gd) have been studied by first principles calculation. The full-potential linearized augmented plane wave method based on density functional theory was employed. For the exchange-correlation potential, local spin density approximation + Coulomb repulsion (LSDA + U) is used to treat the f-electrons more effectively. The numerical values of the elastic parameters are estimated in the framework of the Voigt-Reuss-Hill approximation. OsP-based filled skutterudite with localized 4f and 5d-electrons shows dense energy bands near Fermi energy originating from rare earth and Os atoms. The dense density of states near EF reveals that these compounds are suitable for thermoelectric application. Optical constants including dielectric function, optical reflectivity and refractive index are calculated for photon energy radiation up to 12 eV. The exchange-splitting of R-4f states were analyzed to explain the ferromagnetic behavior of ROs4P12. © 2015 Taylor and Francis.


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.


Shankar A.,Mizoram University | Rai D.P.,Pachhunga University College | Rai D.P.,Beijing Computational Science Research Center | Sandeep,Mizoram University | And 2 more authors.
Phase Transitions | Year: 2015

The elastic, electronic, magnetic and optical properties of filled skutterudite ROs4P12 (R = Sm, Eu and Gd) have been studied by first principles calculation. The full-potential linearized augmented plane wave method based on density functional theory was employed. For the exchange-correlation potential, local spin density approximation + Coulomb repulsion (LSDA + U) is used to treat the f-electrons more effectively. The numerical values of the elastic parameters are estimated in the framework of the Voigt-Reuss-Hill approximation. OsP-based filled skutterudite with localized 4f and 5d-electrons shows dense energy bands near Fermi energy originating from rare earth and Os atoms. The dense density of states near EF reveals that these compounds are suitable for thermoelectric application. Optical constants including dielectric function, optical reflectivity and refractive index are calculated for photon energy radiation up to 12 eV. The exchange-splitting of R-4f states were analyzed to explain the ferromagnetic behavior of ROs4P12. © 2015 Taylor and Francis.


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.


Shankar A.,North Bengal University | Rai D.P.,Pachhunga University College | Sandeep,Mizoram University | Khenata R.,University of Mascara | And 2 more authors.
Journal of Computational Electronics | Year: 2016

The density functional theory (DFT)-based fully relativistic version of the full-potential linearized augmented plane wave method with spin–orbit coupling (SOC) has been used to study the electronic and optical properties of the filled skutterudite CeRu 4As 12. The exchange and correlation potential has been treated with the local density approximation (LDA). The analysis of the density of states and energy bands in the vicinity of the Fermi energy level suggests the semiconducting nature of the material with narrow indirect energy band gap of 0.11 eV; however, the gap value increases to 0.17 eV for without SOC calculation. Additionally, the modified Becke–Johnson (mBJ) potential has been utilized along with the LDA approach to estimate the precise value of the energy band gap of the material. The mBJ treatment enhances the energy band gap to −0.2 eV. In order to understand the structural and mechanical properties of the sample material, the elastic constants are also estimated at ambient conditions. The analysis of the elastic constants suggests the brittle nature of the material whose stiffness is comparable with that of CeOs 4Sb 12 and the covalent contribution is expected in the bonding. The optical response of the material has been studied from the energy bands, which reflects the metallic behavior of the material in the infrared region of frequency radiation and turns to act as opaque material with superluminal behavior at ultraviolet frequency radiation. The inclusion of the hybrid functional in the calculation suggests the metallic nature of the material. © 2016, Springer Science+Business Media New York.


Lalhriatpuia C.,Pachhunga University College | Tiwari A.,National Institute of Technology Tiruchirappalli | Shukla A.,National Institute of Technology Tiruchirappalli | Tiwari D.,Mizoram University | Lee S.M.,Catholic Kwandong University
Korean Journal of Chemical Engineering | Year: 2016

We assessed the photocatalytic behavior of Nanopillars-TiO2 thin films obtained onto a borosilicate glass in the degradation of 17α-ethynylestradiol (EE2) from aqueous solution under batch reactor operations. The thin films were characterized by the XRD, SEM, AFM analytical methods. BET specific surface area and pore sizes were also obtained. The photocatalytic degradation of EE2 using the UV light was studied at wide range of physico-chemical parametric studies to determine the mechanism of degradation as well the practical implacability of the technique. The batch reactor operations were conducted at varied pH (pH 4.0 to 10.0), EE2 initial concentration (1.0 to 5.0mg/L) and presence of several interfering ions, i.e., cadmium nitrate, copper sulfate, zinc chloride, sodium chloride, sodium nitrate, sodium nitrite, glycine, oxalic acid and EDTA in the photocatalytic degradation of EE2. The time dependence photocatalytic degradation of EE2 was demonstrated with the pseudo-first-order rate kinetics. The mineralization of EE2 was assessed using the total organic carbon analysis conducted at varied initial pH and EE2 concentrations. Further, the repeated use of the photocatalyst enhanced the applicability of thin films in the successive photocatalytic operations. © 2016 Korean Institute of Chemical Engineers, Seoul, Korea


Chettri S.,Mizoram University | Rai D.P.,Pachhunga University College | Shankar A.,Mizoram University | Ghimire M.P.,Condensed Matter Physics Research Center | And 2 more authors.
Modern Physics Letters B | Year: 2016

In this paper, the structural, electronic and magnetic properties of Nd-doped rare earth aluminate, La1-xNdxAlO3 (x = 0%-100%) is studied using the first-principles full potential linearized augmented plane wave (FP-LAPW) method. The effects of partial Nd substitution for La in LaAlO3 are studied using supercell calculations. The electronic structure analysis indicates La1-xNdxAlO3 to be a probable half metal within the spin polarized generalized gradient approximation (GGA). The direct and indirect band gaps are reported and were analyzed as a function of concentration of Nd doping on LaAlO3. The calculated magnetic moments in La1-xNdxAlO3 were found to arise mainly from the Nd-4f electrons which manifest the magnetic nature of the system. The significant band gap narrowing with increase in doping concentration may find important applications in optoelectronic devices. © 2016 World Scientific Publishing Company.


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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