Neha Tyagi

Doping induced structural stability and electronic properties of GaN nanotubes.

The present paper discusses the effect of manganese doping on the structural stability and electronic band gap of chiral (2, 1), armchair (3, 3), and zigzag ((6, 0) and (10, 0)) single walled GaN nanotube by using density functional theory based Atomistix Toolkit (ATK) Virtual NanoLab (VNL). The structural stability has been analyzed in terms of minimum ground state total energy, binding, and formation energy. As an effect of Mn doping (1–4 atoms), all the GaN nanotubes taken into consideration show semiconducting to metallic transition first and after certain level of Mn doping changes its trend.

Pressure-induced phase transition and electronic properties of AlN nanowires: an ab initio study

The structural stability of AlN nanowires have been analyzed in wurtzite (B4), zincblende (B3), rocksalt (B1) and CsCl (B2) type phases using density functional theory based ab initio approach. The total energy calculations have been performed in a self-consistent manner using local density approximation as exchange correlation functional. The analysis finds the B4 type phase as most stable amongst the other phases taken into consideration and observes the structural phase transition from B4 → B3, B4 → B1, B4 → B2, B3 → B1 and B3 → B2 at 42.7, 76.54, 142, 30.4 and 108.9 GPa respectively. Lattice parameter, bulk modulus and pressure derivatives of AlN nanowires have also been calculated for all the stable phases. The electronic band structure analysis of AlN nanowires shows a semiconducting nature in its B4, B3 and B1 type phases, whereas the B2 type phase is found to be metallic.

High pressure behavior of AlAs nanocrystals: the first-principle study

In this study, the first-principle density functional approach has been used to analyze the pressure-induced structural stability and phase transformation in AlAs nanocrystals. This study includes the stability analysis of AlAs nanocrystals in their B4-, B3-, B1- and B2-type phases, and we observed that the B3-type phase is the most stable. We also observed the structural transformations in AlAs nanocrystals from B3→B1 at around 8.9 GPa, B3→B2 at 7.12 GPa and B3→B4 at 3.88 GPa. The stability of the materials has been analyzed using local density approximation with the Perdew–Zunger parameterization and also with the Perdew–Burke–Ernzerhof (PBE) and revised PBE parameterizations of the generalized gradient approximation potential.

Electronic properties and migration pathways of Cl functionalized zigzag graphene nanoribbons

We have investigated the electronic properties of pristine and Cl functionalized zigzag graphene nanoribbons (ZGNR) by employing density functional theory (DFT) based calculations. The migration pathways of Cl adatom adsorption on Cl functionalized ZGNR are also discussed. It is revealed that Cl functionalization results in additional electronic states across the Fermi level which enhances the metallic character of ZGNR. Interestingly, it is predicted that migration of Cl adatom on ZGNR network is most likely to take place along the ribbon edges whereas migration across the ribbon width is found least energetically favorable.We have investigated the electronic properties of pristine and Cl functionalized zigzag graphene nanoribbons (ZGNR) by employing density functional theory (DFT) based calculations. The migration pathways of Cl adatom adsorption on Cl functionalized ZGNR are also discussed. It is revealed that Cl functionalization results in additional electronic states across the Fermi level which enhances the metallic character of ZGNR. Interestingly, it is predicted that migration of Cl adatom on ZGNR network is most likely to take place along the ribbon edges whereas migration across the ribbon width is found least energetically favorable.

Pressure induced phase transition and electronic properties of GaN nanocrystals: Ab-initio study

We have analysed a zincblende (B3) to rocksalt (B1) type structural phase transition in ∼0.7nm GaN nanocrystals (NCs) under high compression. The computed minimum total energy and binding energy per atom confirms the stability of B3 type phase. The equilibrium lattice parameter, bulk modulus and pressure derivative for both the phases are calculated and a comparative analysis shows that the bulk moduli of NCs are relatively lower than their bulk counterparts, suggests the softening of material at reduced dimension. Under compression at around 100 GPa the B3 type phase of NC transforms to B1 type phase. Interestingly, the computed band gaps of NCs are relatively lower than their bulk crystal, which is in contrast to the quantum confinement effect, can be explained in terms of the bond length that gets changed at nanoscale.

Structural phase transition and electronic properties of AlSb nanocrystal

Density functional theory (DFT) based ab-initio approach has been used to investigate the structural stability of ∼1nm sized AlSb nanocrystal in its zinc blende (B3), rocksalt (B1) and CsCl (B2) type phases under high compression. The self consistent total energy calculations have been performed for analyzing the stability of the material and found that B3 type phase is most stable amongst the other considered phases. It is revealed that under compression, the original B3 type phase of AlSb nanocrystal transforms to B1 type phase at a pressure of about 8.9 GPa, which is larger than that of bulk crystal. The ground state properties such as lattice parameter, bulk modulus and pressure derivative have been calculated for all the three stable phases of AlSb nanocrystal. The electronic band structure analysis finds that the band gap of AlSb nanocrystal in its most stable (B3) phase is comparatively lower than its bulk counterpart.

Structural Stability of GaAs Nanocrystal

We have used the first principle density functional approach for analyzing the structural stability of GaAs nanocrystal (NC) in various possible phases like wurtzite (B4), NiAs (B8), zincblende (B3), CsCl (B2) and NaCl (B1). The study reveals that the stable B3 phase of bulk GaAs is unstable in its nanocrystal and better stabilizes in wurtzite (B4) type phase. The study has been performed using local density approximation (LDA) with the Perdew‐Zunger(PZ) parameterization and Perdew‐Burke‐Ernzerhof(PBE) and Revised Perdew‐Burke‐Ernzerhof (revPBE) parameterization of the GGA potential. The calculated lattice parameter of bulk GaAs is in close agreement with its experimental counterpart.

Structural, magnetic and electronic properties of armchair graphene nanoribbons interacting with Co: DFT investigations

ABSTRACT Theoretical investigations based on density functional theory (DFT) have been performed to reveal the effect of Co impurities on structural stability, magnetic and electronic properties of armchair graphene nanoribbons (AGNR). It is revealed that Co forms stable chemical bonding with host (C) atoms and settled in magnetic ground state. Calculated magnetic moment per Co atom was found to be 1.02–1.67 µB. Moreover, up to ∼70% spin polarization is also predicted which is a function of doping site. Present findings are useful to induce width independent metallicity in AGNR making them a potential candidate for contact/interconnect applications in upcoming nano-devices.

Spintronic and transport properties of linear atomic strings of transition metals (Fe, Co, Ni)

In the present work, first-principles investigations have been performed to study the spintronic and transport properties of linear atomic strings of Fe, Co and Ni. The structural stabilities of the considered strings were compared on the basis of binding energies which revealed that all the strings are energetically feasible to be achieved. Further, all the considered strings are found to be ferromagnetic and the observed magnetic moment ranges from 1.38 to 1.71 μB. The observed transport properties and high spin polarization points towards their potential for nano interconnects and spintronic applications.

Pressure induced zincblende to rocksalt phase transition in AlN nanocrystal

Structural phase transition in Aluminium nitride (AlN) nanocrystal has been studied within the framework of density-functional theory, using both the local-density as well as generalized gradient approximation as exchange correlation functionals. The study observes that under the application of pressure AlN nanocrystal transforms from its original zincblende (B3) type phase to hypothetical rocksalt (B1) type phase within the pressure range of 46GPa to 56GPa, which is comparatively larger than its bulk counterpart. The lattice parameter, bulk modulus and pressure derivatives of AlN nanocrystal in its original B3 type phase as well as hypothetical B1 type phase have also been computed as ground state properties. The mechanical strength of the AlN nanocrystal has been analysed in terms of volume collapse at transition pressure and bulk modulus.