School Of Basic And Applied Sciences
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Item Recent advances in 2D anode materials for Na-ion batteries from a theoretical perspective(Taylor and Francis Ltd., 2023-11-02T00:00:00) Verma, Nidhi; Jamdagni, Pooja; Kumar, Ashok; Srivastava, Sunita; Tankeshwar, K.Na-ion batteries (SIBs) are a promising replacement for lithium-ion batteries (LIBs) for low-cost and large-scale energy storage systems in the forthcoming years after additional in-depth examination and investigation. A significant part of the development of innovative anode materials and their in-depth understanding has come through simulations. Ab initio simulations based on density functional theory (DFT) have been proven to be a reliable, efficient, and cost-effective way to design new anode materials for SIBs. As a result of the identification of graphene, researchers and scientists were influenced to create new two-dimensional (2D) materials. On account of their distinctive physical and chemical properties, the broad expanse of surface, innovative electronic features, and charging ability of 2D materials attract much attention. Many of these characteristics are significant prerequisites for using anodes in batteries. Herein, based on recent research progress, we have reviewed the structures and electrochemical properties of 2D materials as anode for Na-ion batteries from a theoretical perspective. The effective methodologies for high-performance anode materials are provided based on the substantial literature and theoretical studies. Added to that, we have also explored the various techniques such as heterostructure, doping, defect- and strain-engineering of 2D materials for the improvement of the performance of these materials as anodes for SIBs. � 2023 Taylor & Francis Group, LLC.Item Janus ?-PdXY (X/Y = S, Se, Te) materials with high anisotropic thermoelectric performance(Royal Society of Chemistry, 2023-02-21T00:00:00) Jakhar, Mukesh; Sharma, Raman; Kumar, AshokTwo-dimensional (2D) materials have garnered considerable attention as emerging thermoelectric (TE) materials owing to their unique density of states (DOS) near the Fermi level. We investigate the TE performance of Janus ?-PdXY (X/Y = S, Se, Te) monolayer materials as a function of carrier concentration and temperature in the mid-range from 300 to 800 K by combining density functional theory (DFT) and semi-classical Boltzmann transport theory. The phonon dispersion spectra and AIMD simulations confirm their thermal and dynamic stability. The transport calculation results reveal the highly anisotropic TE performance of both n and p-type Janus ?-PdXY monolayers. Meanwhile, the coexistence of low phonon group velocity and a converged scattering rate leads to a lower lattice thermal conductivity (Kl) of 0.80 W mK?1, 0.94 W mK?1, and 0.77 W mK?1 along the y-direction for these Janus materials, while the high TE power factor is attributed to the high Seebeck coefficient (S) and electrical conductivity, which are due to the degenerate top valence bands of these Janus monolayers. The combination of lower Kl and a high-power factor at 300 K (800 K) leads to an optimal figure of merit (ZT) of 0.68 (2.21), 0.86 (4.09) and 0.68 (3.63) for p-type Janus PdSSe, PdSeTe and PdSTe monolayers, respectively. To evaluate rational electron transport properties, the effects of acoustic phonon scattering (?ac), impurity scattering (?imp), and polarized phonon scattering (?polar) are included in the temperature-dependent electron relaxation time. These findings indicated that the Janus ?-PdXY monolayers are promising candidates for TE conversion devices. � 2023 The Royal Society of Chemistry.Item Gold�Hydrogen Analogy in Small�Sized Hydrogen�Doped Gold Clusters Revisited(John Wiley and Sons Inc, 2022-07-12T00:00:00) Megha; Mondal, Krishnakanta; Ghanty, Tapan K.; Banerjee, ArupThe analogy between gold and hydrogen is a subject of long-standing debate. In the present work, we examine the validity of the gold-hydrogen analogy in a series of small-sized H-doped gold clusters, Aun?1H with n varying between 2 and 10 and also investigate its dependence on the cluster size. Keeping in mind the importance of the role of structures, we make use of the genetic algorithm coupled with a density functional theory based method to exhaustively search and identify the energetically low-lying structures of each of the H-doped gold clusters. These lower energy structures of H-doped and pristine gold clusters are then employed to carry out the calculations of their electronic properties, stability analysis as well as their reactivity towards the adsorption and activation of CO and O2 molecules. Our study shows that in line with the gold-hydrogen analogy, both electronic properties and the adsorption/activation characteristics of H-doped gold clusters remain very similar to those of pristine gold clusters. � 2022 Wiley-VCH GmbH.Item Stability, optoelectronic and thermal properties of two-dimensional Janus ?-Te2S(IOP Publishing Ltd, 2022-02-14T00:00:00) Singh, Jaspreet; Jakhar, Mukesh; Kumar, AshokMotivated by recent progress in the two-dimensional (2D) materials of group VI elements and their experimental fabrication, we have investigated the stability, optoelectronic and thermal properties of Janus ?-Te2S monolayer using first-principles calculations. The phonon dispersion and MD simulations confirm its dynamical and thermal stability. The moderate band gap ( 1/41.5 eV), ultrahigh carrier mobility ( 1/4103 cm2 V-1 s-1), small exciton binding energy (0.26 eV), broad optical absorption range and charge carrier separation ability due to potential difference ( "V = 1.07 eV) on two surfaces of Janus ?-Te2S monolayer makes it a promising candidate for solar energy conversion. We propose various type-II heterostructures consisting of Janus ?-Te2S and other transition metal dichalcogenides for solar cell applications. The calculated power conversion efficiencies of the proposed heterostructures, i.e. ?-Te2S/T-PdS2, ?-Te2S/BP and ?-Te2S/H-MoS2 are 1/421%, 1/419% and 18%, respectively. Also, the ultralow value of lattice thermal conductivity (1.16 W m-1 K-1) of Janus ?-Te2S makes it a promising material for the fabrication of next-generation thermal energy conversion devices. � 2022 IOP Publishing Ltd.Item Pressure and electric field tuning of Schottky contacts in PdSe2/ZT-MoSe2 van der Waals heterostructure(Institute of Physics Publishing, 2020) Jakhar, M; Singh, J; Kumar, A; Tankeshwar, K.A two-dimensional van der Waals (vdW) heterostructure (PdSe2/ZT-MoSe2) has been investigated through vdW corrected density functional theory. ZT-MoSe2 acts as a Dirac material with an anisotropic Dirac cone and variable Fermi velocity (0.52-1.91 105 ms-1). The intrinsic Schottky barrier height can be effectively tuned by applying external pressure and an electric field to the heterostructure. The p-type Schottky barrier transforms into a p-type ohmic contact at pressure P ? 16 GPa. A positive electric field induces p-type ohmic contact while a negative electric field results in the transition from p-type Schottky contact to n-type Schottky contact, and finally to n-type ohmic contact at the higher values of the field. Moreover, the external positive (negative) electric field induces n-type (p-type) doping of ZT-MoSe2 in the heterostructure and remarkably controls the charge carrier concentration. Our results demonstrate that controlling the external pressure and electric field in a PdSe2/ZT-MoSe2 heterostructure can result in an unprecedented opportunity for the design of high-performance nanodevices. � 2020 IOP Publishing Ltd.Item Novel phosphorus-based 2D allotropes with ultra-high mobility(Institute of Physics Publishing, 2020) Kaur, S; Kumar, A; Srivastava, S; Tankeshwar, K; Pandey, R.Electronic structure calculations based on density functional theory were performed to investigate structural, mechanical, and electronic properties of phosphorene-based large honeycomb dumbbell (LHD) hybrid structures and a new phosphorene allotrope, referred to as ??-P. The LHD hybrids (i.e., X6P4; X being C or Si or Ge or Sn) and ??-P have significantly higher bandgaps than the corresponding pristine LHD structures, except the case of C6P4, which is metallic. ??-P is found to be a highly flexible p-type material which shows strain-engineered photocatalytic activity in a highly alkaline medium. The carrier mobility of the considered systems is as high as 105 cm2 V-1 s-1 (specifically the electron mobility of LHD structures). The calculated STM images display the surface morphologies of the LHD hybrids and ??-P. The predicted phosphorus-based 2D structures with novel electronic properties may be candidate materials for nanoscale devices. - 2020 IOP Publishing Ltd.