Condensed Matter Physics Research Center

Lumbini, Nepal

Condensed Matter Physics Research Center

Lumbini, Nepal
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Shankar A.,Mizoram University | Rai D.P.,Pachhunga University College | Sandeep,Mizoram University | Ghimire M.P.,Condensed Matter Physics Research Center | Thapa R.K.,Mizoram University
Indian Journal of Physics | Year: 2017

On the basis of the first-principles density functional theory (DFT), we have investigated the electronic structure, elastic and magnetic properties of the filled skutterudite EuRu4As12 using the full-potential linearized augmented plane wave (FP-LAPW) method. The calculations presented here are carried out within the framework of the local spin density approximation (LSDA) approach. The effects of the localized electrons are treated by including Hubbard’s U term in the calculation. The study of the elastic properties suggests the brittle nature of the material with covalent contribution in the atomic bonding. EuRu4As12 is a semi-metal with the presence of the bands originating from the bottom of the conduction region crossing the Fermi energy level (EF) more than twice. The existence of the high density of states at EF implies the large thermopower of the material and likely to be an effective candidate for the thermoelectric application. The exchange-splitting of Eu-f states are analyzed to explain the ferromagnetic ground state of the material. The analysis of the thermal transport properties suggests the high value of Seebeck coefficient of the material with figure of merit (ZT) value of 0.55, which is consistent with the values obtained for the analogous compounds. © 2016, Indian Association for the Cultivation of Science.


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.


Ghimire M.P.,Nepal Academy of Science and Technology | Ghimire M.P.,Condensed Matter Physics Research Center | Sandeep,Mizoram University | Sinha T.P.,Bose Institute of India | Thapa R.K.,Mizoram University
Journal of Alloys and Compounds | Year: 2011

The electronic density of states (DOS), magnetic moments and band structure of semi-Heusler alloy NiXSb (where X = Ti, V, Cr and Mn) has been studied by using the first principles full-potential linearized augmented plane wave method (FP-LAPW) based on density functional theory (DFT). For the exchange and correlation potential generalized-gradient approximation (GGA) is used. From the observations, NiTiSb shows the possibility of half-metallic ferromagnet (HMF) behavior with a band gap of 0.53 eV and an effective moment of 0.35 μB. The alloys like NiVSb, NiCrSb and NiMnSb are HMF with band gap of 0.49 eV, 0.38 eV and 0.48 eV and an effective moment of 1.995 μB, 3.01 μB and 3.99 μB respectively. DOS and band structure result shows the 3d states of Ni overlap with 3d states of X atoms suggesting hybridization between them. The exchange-splitting of Ni-3d and X-3d state electrons lead to localized spin moment which determines the HMF behavior of NiXSb. The results obtained are compared and found to be in close agreement with the available data. © 2011 Elsevier B.V.


Rai D.P.,Beijing Computational Science Research Center | Rai D.P.,Mizoram University | Shankar A.,Mizoram University | Ghimire M.P.,Japan International Center for Materials Nanoarchitectonics | And 2 more authors.
Computational Materials Science | Year: 2015

A density functional theory (DFT) employing generalized gradient approximation (GGA) and modified Becke Johnson (TB-mBJ) potential have been used to study the electronic, magnetic and optical properties of A2FeReO6 (AFRO). The presence of indirect band gap of majority electrons at EF and the conducting behaviour of minority electrons predicts these materials to be a half metallic ferrimagnets. The GGA band gaps are enhanced with the implementation of a new electron exchange semilocal potential called TB-mBJ. The real and imaginary parts of dielectric function, refractive index, absorption coefficient and reflectivity are calculated. The inter-band transitions to the optical properties are analyzed with the band structures. © 2015 Elsevier B.V. All rights reserved.


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.


Ghimire M.P.,Nepal Academy of Science and Technology | Ghimire M.P.,Condensed Matter Physics Research Center | Sandeep,Mizoram University | Sinha T.P.,Bose Institute of India | And 2 more authors.
Physica B: Condensed Matter | Year: 2011

The electronic density of states (DOS), band structure and optical properties of orthorhombic SbTaO4 are studied by first principles full potential-linearized augmented plane wave (FP-LAPW) method. The calculation is done in the framework of density functional theory with the exchange and correlation effects treated using generalized gradient approximation (GGA). We find an indirect band gap of 1.9 eV at the R→Γ symmetry direction of the Brillouin zone in SbTaO4. It is observed that there is a strong hybridization between Ta-5d and O-2p electronic states which is responsible for the electronic properties of the system. Using the projected DOS and band structure we have analyzed the interband contribution to the optical properties of SbTaO4. The real and imaginary parts of the dielectric function of SbTaO4 are calculated, which correspond to electronic transitions from the valence band to the conduction band. The band gap obtained is in close agreement with the experimental data. © 2011 Elsevier B.V. All rights reserved.


Sandeep,Mizoram University | Rai D.P.,Mizoram University | Shankar A.,North Bengal University | Ghimire M.P.,Condensed Matter Physics Research Center | And 2 more authors.
Journal of Magnetism and Magnetic Materials | Year: 2016

The structural, electronic and magnetic properties of Nd-doped Rare earth aluminate, La1-xNdxAlO3 (x=0-100%) are studied using the full potential linearized augmented plane-wave (FP-LAPW) method within the density functional theory. The effects of Nd substitution in LaAlO3 are studied using super-cell calculations. The electronic structures were computed using modified Beck Johnson (mBJ) potential based approximation with the inclusion of Coulomb energy (U) for Nd-4f state electrons. The La1-xNdxAlO3 may possess half metallic behavior on Nd doping with finite density of states at EF. The direct and indirect band gaps were studied as a function of Nd concentration in LaAlO3. The calculated magnetic moments in La1-xNdxAlO3 were found to arise mainly from the Nd-4f state electrons. A probable half-metallic nature is suggested for these systems with supportive integral magnetic moments and high spin polarized electronic structures in these doped cases at EF. The controlled decrease in band gap with increase in concentration of Nd doping is a suitable technique for harnessing useful spintronic and magnetic devices. © 2016 Elsevier B.V. All rights reserved.


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.


Sandeep,Mizoram University | Ghimire M.P.,Nepal Academy of Science and Technology | Thapa R.K.,Mizoram University | Thapa R.K.,Condensed Matter Physics Research Center
Journal of Magnetism and Magnetic Materials | Year: 2011

The density of states (DOS) and the magnetic moments of SmCrSb3 and GdCrSb3 have been studied by first principles full-potential linearized augmented plane wave (FP-LAPW) method based on density functional theory (DFT). For the exchange-correlation potential, the local-spin density approximations with correlation energy (LSDAU) method have been used. Total and partial DOS have been computed using the WIEN2k code. DOS result shows the exchange-splittings of Cr-3d and rare-earth (R) 4f states electrons, which are responsible for the ground state ferromagnetic (FM) behavior of the systems. The FM behavior of these systems is strongly influenced by the average number of Cr-3d and Sm (Gd) 4f-electrons. The effective moment of SmCrSb3 is found to be 7.07 μB while for GdCrSb3 it is 8.27 μB. The Cr atom plays a significant role on the magnetic properties due to the hybridization between Cr-3d and Sb-5p states. © 2011 Elsevier B.V. All rights reserved.


Ghimire M.P.,Condensed Matter Physics Research Center | Ghimire M.P.,Mizoram University | Thapa R.K.,Condensed Matter Physics Research Center | Thapa R.K.,Mizoram University
Advanced Science Letters | Year: 2015

We have studied the electronic and magnetic properties of double perovskites Gd2MgIrO6 by first-principles density functional theory (DFT). Based on the DFT calculations, Gd2MgIrO6 is found to have a ferromagnetic (FM) ground state. The material undergo half-metallic ferromagnets to Mott-Hubbard insulator transition which happens due to strong correlation in Gd–4f and Ir–5d states. Our results shows that the 5d electrons of Ir hybridize strongly with O–2p states near the Fermi level giving rise to the insulating state of Gd2MgIrO6. Our study suggests that the enhanced magnetic moment is a result of itinerant exchange rather than the exchange interaction involving individual ions of Gd and Ir atoms. The total magnetic moment calculated in the present studies is 15 μB per formula unit for Gd2MgIrO6. © 2015 American Scientific Publishers. All rights reserved.

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