Physics - Research Publications

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Author: search.filters.author.Tankeshwar, K.Subject: search.filters.subject.Density functional theory

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    Photocatalytic properties of anisotropic ?-PtX2 (X = S, Se) and Janus ?-PtSSe monolayers
    (Royal Society of Chemistry, 2022-09-01T00:00:00) Jamdagni, Pooja; Kumar, Ashok; Srivastava, Sunita; Pandey, Ravindra; Tankeshwar, K.
    The highly efficient photocatalytic water splitting process to produce clean energy requires novel semiconductor materials to achieve a high solar-to-hydrogen energy conversion efficiency. Herein, the photocatalytic properties of anisotropic ?-PtX2 (X = S, Se) and Janus ?-PtSSe monolayers were investigated based on the density functional theory. The small cleavage energy for ?-PtS2 (0.44 J m?2) and ?-PtSe2 (0.40 J m?2) endorses the possibility of mechanical exfoliation from their respective layered bulk materials. The calculated results revealed that the ?-PtX2 monolayers have an appropriate bandgap (?1.8-2.6 eV) enclosing the water redox potential, light absorption coefficient (?104 cm?1), and exciton binding energy (?0.5-0.7 eV), which facilitates excellent visible-light-driven photocatalytic performance. Remarkably, the inherent structural anisotropy leads to an anisotropic high carrier mobility (up to ?5 � 103 cm2 V?1 S?1), leading to a fast transport of photogenerated carriers. Notably, the required small external potential to realize hydrogen evolution reaction and oxygen evolution reaction processes with an excellent solar-to-hydrogen energy conversion efficiency for ?-PtSe2 (?16%) and ?-PtSSe (?18%) makes them promising candidates for solar water splitting applications. � 2022 The Royal Society of Chemistry.
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    Stability and carrier transport properties of phosphorene-based polymorphic nanoribbons
    (Institute of Physics Publishing, 2018) Kaur, Sumandeep; Kumar, Ashok; Srivastava, Sunita; Pandey, Ravindra; Tankeshwar, K.
    Few-layer black phosphorene has recently attracted significant interest in the scientific community. In this paper, we consider several polymorphs of phosphorene nanoribbons (PNRs) and employ deformation potential theory within the effective mass approximation, together with density functional theory, to investigate their structural, mechanical and electronic properties. The results show that the stability of a PNR strongly depends on the direction along which it can be cut from its 2D counterpart. PNRs also exhibit a wide range of line stiffnesses ranging from 6 ?1010 eV m-1 to 18 ?1011 eV m-1, which has little dependence on the edge passivation. Likewise, the calculated electronic properties of PNRs show them to be either a narrow-gap semiconductor (E g < 1 eV) or a wide-gap semiconductor (E g > 1 eV). The carrier mobility of PNRs is found to be comparable to that of black phosphorene. Some of the PNRs show an n-type (p-type) semiconducting character owing to their higher electron (hole) mobility. Passivation of the edges leads to n-type ? p-type transition in many of the PNRs considered. The predicted novel characteristics of PNRs, with a wide range of mechanical and electronic properties, make them potentially suitable for use in nanoscale devices. ? 2018 IOP Publishing Ltd.
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    Ultra-narrow blue phosphorene nanoribbons for tunable optoelectronics
    (Royal Society of Chemistry, 2017) Swaroop, Ram; Ahluwalia, P. K.; Tankeshwar, K.; Kumar, Ashok
    We report optoelectronic properties of ultra-narrow blue phosphorene nanoribbons (BPNRs) within the state-of-the-art density functional theory framework. The positive but small value of formation energy (?0.1 eV per atom) indicates the relative ease of the formation of BPNRs from their two-dimensional (2D) counterpart. The oscillatory behaviour of the electronic band gap of bare BPNRs with increasing width is attributed to the reconstruction of edge atoms. The static dielectric constant of BPNRs depends on the width and applied strain which in turn shows consistency with the Penn's model expression for semiconductors. Bare BPNRs exhibit both ? and ? + ? plasmonic structures while passivated ones possess only a ? + ? plasmonic structure that get blue-shifted (as large as ?3 eV) on increasing the width of the BPNRs which makes electron energy loss spectroscopy useful for identifying the width of BPNRs in real experimental situations. The mechanical strain induces a small red shift in, which is attributed to the modification in electronic band dispersion due to a different superposition of atomic orbitals on the application of applied strain. These tunable electronic and dielectric properties of BPNRs mean they may find applications in optoelectronic devices based on blue phosphorene. ? The Royal Society of Chemistry.