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Paranthaman, Selvarengan,Moon, Jiwon,Kim, Joonghan,Kim, Dong Eon,Kim, Tae Kyu American Chemical Society 2016 The Journal of physical chemistry A Vol.120 No.13
<P>Herein a performance assessment of density functionals used for calculating the structural and energetic parameters of bi-and trimetallic Ru-containing organometallic complexes has been performed. The performance of four popular relativistic effective core potentials (RECPs) has also been assessed. On the basis of the calculated results, the MN12-SX (range-separated hybrid functional) demonstrates good performance for calculating the molecular structures, while MN12-L (local functional) performs well for calculating the energetics, including that of the Ru-Ru bond breaking process. The choice of appropriate density functional is a crucial factor for calculating the energetics. The LANLO8 demonstrates the lowest performance of the RECPs for calculating the molecular structures, especially the Ru-Ru bond length.</P>
Paranthaman, Selvarengan,Hong, Kiryong,Kim, Joonghan,Kim, Dong Eon,Kim, Tae Kyu American Chemical Society 2013 The journal of physical chemistry. A, Molecules, s Vol.117 No.38
<P>We report the results of a benchmarking study on hybrid, hybrid-meta, long-range-corrected, meta-generalized gradient approximation (meta-GGA), and GGA density functional theory (DFT) methods for aluminum (Al) clusters. A range of DFT functionals, such as B3LYP, B1B95, PBE0, mPW1PW91, M06, M06-2X, ωB97X, ωB97XD, TPSSh, BLYP, PBE, mPWPW91, M06-L, and TPSS, have been used to optimize the molecular structures and calculate the vibrational frequencies and four energetic parameters for neutral and anionic Al<SUB><I>n</I></SUB> (<I>n</I> = 2–10) clusters. The performances of these functionals are assessed systematically by calculating the vertical ionization energy for neutral Al clusters and the vertical electron detachment energy for anionic Al clusters, along with the cohesive energy and dissociation energy. The results are compared with the available experimental and high-level ab initio calculated results. The calculated results showed that the PBE0 and mPW1PW91 functionals generally provide better results than the other functionals studied. TPSS can be a good choice for the calculations of very large Al clusters. On the other hand, the B3LYP, BLYP, and M06-L functionals are in poor agreement with the available experimental and theoretical results. The calculated results suggest that the hybrid DFT functionals like B3LYP do not always provide better performance than GGA functionals.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/jpcafh/2013/jpcafh.2013.117.issue-38/jp4074398/production/images/medium/jp-2013-074398_0007.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/jp4074398'>ACS Electronic Supporting Info</A></P>
Compact wideband implantable antenna for biomedical applications
Mohanraj Paranthaman,Selvakumaran Palanivel Rajan 한국물리학회 2022 Current Applied Physics Vol.43 No.-
Wideband miniaturized antenna along with high gain is much needed for biomedical implantable applications. Square patch with loop structure of 51.2 mm3 (8 mm × 8 mm × 0.8 mm) volume is printed on RT Duroid 5880 (εr = 2.2) low permittivity substrate. Parametric study is conducted to optimize the antenna structure. Tissue model is used to take the simulation results and Body Equivalent Solution is used for measuring the antenna performance. Good radiation performance is confirmed by obtaining a gain of -16.7 dBi at 2.45 GHz and a low SAR value of 35.03 W/kg over 10g tissue with input power 1W is obtained. Proposed antenna gives a 64.9% measured wide impedance bandwidth. This study reveals that simple antenna structure can provide good performance when it is placed in complicated environment.
Nanoparticle Shape Evolution and Proximity Effects During Tip-Induced Electrochemical Processes
Yang, Sang Mo,Paranthaman, Mariappan Parans,Noh, Tae Won,Kalinin, Sergei V.,Strelcov, Evgheni American Chemical Society 2016 ACS NANO Vol.10 No.1
<P>Voltage spectroscopies in scanning probe microscopy (SPM) techniques are widely used to investigate the electrochemical processes in nanoscale volumes, which are important for current key applications, such as batteries, fuel cells, catalysts, and memristors. The spectroscopic measurements are commonly performed on a grid of multiple points to yield spatially resolved maps of reversible and irreversible electrochemical functionalities. Hence, the spacing between measurement points is an important parameter to be considered, especially for irreversible electrochemical processes. Here, we report nonlocal electrochemical dynamics in chains of Ag particles fabricated by the SPM tip on a silver ion solid electrolyte. When the grid spacing is small compared with the size of the formed Ag particles,, anomalous chains of unequally sized particles with double periodicity evolve. This behavior is ascribed to a proximity effect during the tip-induced electrochemical process, specifically, size-dependent silver particle growth following the contact between the particles. In addition, fractal shape evolution of the formed Ag structures indicates that the growth-limiting process changes from Ag+/Ag redox reaction to Ag+-ion diffusion with the increase in the applied voltage and pulse duration. This study shows that characteristic shapes of the electrochemical products are good indicators for determining the underlying growth-limiting process, and emergence of complex phenomena during spectroscopic mapping of electrochemical functionalities.</P>
Yang, Sang Mo,Strelcov, Evgheni,Paranthaman, M. Parans,Tselev, Alexander,Noh, Tae Won,Kalinin, Sergei V. American Chemical Society 2015 NANO LETTERS Vol.15 No.2
<P>Scanning probe microscopy (SPM) is a powerful tool to investigate electrochemistry in nanoscale volumes. While most SPM-based studies have focused on reactions at the tip–surface junction, charge and mass conservation requires coupled and intrinsically nonlocal cathodic and anodic processes that can be significantly affected by ambient humidity. Here, we explore the role of water in both cathodic and anodic processes, associated charge transport, and topographic volume changes depending on the polarity of tip bias. The first-order reversal curve current–voltage technique combined with simultaneous detection of the sample topography, referred to as FORC-IVz, was applied to a silver solid ion conductor. We found that the protons generated from water affect silver ionic conduction, silver particle formation and dissolution, and mechanical integrity of the material. This work highlights the dual nature (simultaneously local and nonlocal) of electrochemical SPM studies, which should be considered for comprehensive understanding of nanoscale electrochemistry.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/nalefd/2015/nalefd.2015.15.issue-2/nl5040286/production/images/medium/nl-2014-040286_0009.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/nl5040286'>ACS Electronic Supporting Info</A></P>
Controlled synthesis of mesoporous codoped titania nanoparticles and their photocatalytic activity
Mathis, John E.,Kidder, Michelle K.,Li, Yunchao,Zhang, Jinshui,Paranthaman, M.P. Techno-Press 2016 Advances in nano research Vol.4 No.3
The photocatalytic (PC) activity of anatase titania nanoparticles can be improved through codoping with transition metals and nitrogen. In addition, the PC activity can also be improved by creating monodisperse, mesoporous nanoparticles of titania. The question naturally arose as to whether combining these two characteristics would result in further improvement in the PC activity or not. Herein, we describe the synthesis and photocatalytic characteristics of codoped, monodisperse anatase titania. The transition metals tested in the polydisperse and the monodisperse forms were Mn, Co, Ni, and Cu. In each case, it was found that the monodisperse version had a higher PC activity compared to the corresponding polydisperse version.
Strategic coating of NdFeB magnets with Dy to improve the coercivity of permanent magnets
Ucar, Huseyin,Parker, David S.,Nlebedim, I.C.,McCallum, R.W.,McCall, S.K.,Parans Paranthaman, M. Techno-Press 2015 Advances in materials research Vol.4 No.4
We present a method, supported by theoretical analysis, for optimizing the usage of the critical rare earth element dysprosium in $Nd_2Fe_{14}B$ (NdFeB)-based permanent magnets. In this method, we use Dy selectively in locations such as magnet edges and faces, where demagnetization factors are largest, rather than uniformly throughout the bulk sample. A200 nm thick Dy film was sputtered onto a commercial N-38, NdFeB magnets with a thickness of 3 mm and post-annealed at temperatures from $600-700^{\circ}C$. Magnets displayed enhanced coercivities after post-annealing and as much as a 5 % increase in the energy product, while requiring a total Dy content of 0.06 wt. % - a small fraction of that used in the commercial grade Dy-NdFeB magnets. By assuming all Dy diffused into NdFeB magnets, the improvement in energy product corresponds to a saving of over 1% Dy (critical element). Magnets manufactured using this technique will therefore be higher performing which would potentially broaden the application space of these magnets in the traction motors of hybrid and pure electric vehicles, and wind generators.