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Magnetic properties of narrow zig-zag graphene nanoribbons from ab initio calculations

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dc.contributor.advisor Casula, Michele en_US
dc.contributor.author MEENA, RAGHAVENDRA en_US
dc.date.accessioned 2020-06-11T09:56:33Z
dc.date.available 2020-06-11T09:56:33Z
dc.date.issued 2020-05 en_US
dc.identifier.uri http://dr.iiserpune.ac.in:8080/xmlui/handle/123456789/4674
dc.description.abstract The graphene nanoribbons are one-dimensional strips of graphene, which are intensively studied because of their remarkable electronic and magnetic properties. In this work, we have studied the zig-zag type ribbons, because it has already been proposed that magnetic edges-states, present in the ground state at the Fermi, could be relevant for spintronic applications. In this report, we have tried to give a reliable description of the ground state of the zig-zag ribbons. At the density functional theory (DFT) level, it is believed that the antiferromagnetic phase is the ground state for both molecular and extended systems. However, the DFT results quantitatively depend on the chosen functional. Moreover, quantum Monte Carlo (QMC), a more accurate high-level theory, predicts the paramagnetic phase to be the ground state for the acene series, the molecular analogue of the narrowest zig-zag graphene nanoribbons. Since these systems are strongly correlated, DFT needs to be validated against a benchmark theory, such as QMC. In this report, we carry out extensive variational and diffusion QMC calculations, and we show that in the ribbon the antiferromagnetic phase is energetically more stable than the simple paramagnetic wavefunction. The QMC energy gains and the magnetic moments are comparable to those obtained by the DFT-GauPBE exchange-correlation (XC) functional. It turns out that the energetics of static magnetic configurations at the GauPBE level is more accurate than the one from the PBE XC-functional for such a strongly correlated system. en_US
dc.description.sponsorship Erasmus+ Fellowship; INSPIRE by DST. en_US
dc.language.iso en en_US
dc.subject Density functional theory (DFT) en_US
dc.subject Quantum Monte Carlo (QMC) en_US
dc.subject Magnetic phases en_US
dc.subject Zig-zag graphene nanoribbons en_US
dc.subject Spintronics en_US
dc.subject Computational physics en_US
dc.subject 2020 en_US
dc.title Magnetic properties of narrow zig-zag graphene nanoribbons from ab initio calculations en_US
dc.type Thesis en_US
dc.type.degree BS-MS en_US
dc.contributor.department Dept. of Chemistry en_US
dc.contributor.registration 20151121 en_US


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  • MS THESES [1705]
    Thesis submitted to IISER Pune in partial fulfilment of the requirements for the BS-MS Dual Degree Programme/MSc. Programme/MS-Exit Programme

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