01973nas a2200181   4500008004100000022001400041245015400055210006900209260012500278300001100403490000800414520116400422100001601586700002101602700002001623700001801643856013001661       2013                        eng d  a0021-960600aCorrelation between the variation in observed melting temperatures and structural motifs of the global minima of gallium clusters: an ab initio study0 aCorrelation between the variation in observed melting temperatur  aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScJAN  a0143030 v1383 a<p>We have investigated the correlation between the variation in the melting temperature and the growth pattern of small positively charged gallium clusters. Significant shift in the melting temperatures was observed for a change of only few atoms in the size of the cluster. Clusters with size between 31-42 atoms melt between 500-600 K whereas those with 46-48 atoms melt around 800 K. Density functional theory based first principles simulations have been carried out on Ga-n(+) clusters with n = 31, ... , 48. At least 150 geometry optimizations have been performed towards the search for the global minima for each size resulting in about 3000 geometry optimizations. For gallium clusters in this size range, the emergence of spherical structures as the ground state leads to higher melting temperature. The well-separated core and surface shells in these clusters delay isomerization, which results in the enhanced stability of these clusters at elevated temperatures. The observed variation in the melting temperature of these clusters therefore has a structural origin. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4772470]</p>1 aSusan, Anju1 aKibey, Aniruddha1 aKaware, Vaibhav1 aJoshi, Kavita  uhttps://library.ncl.res.in/content/correlation-between-variation-observed-melting-temperatures-and-structural-motifs-global-002057nas a2200217   4500008004100000245008000041210006900121260011700190300003200307490000900339520122200348100001701570700002201587700002501609700002001634700002001654700002201674700001801696700001701714856010801731       2014                        eng d00aDesign and engineering of organic molecules for customizable terahertz tags0 aDesign and engineering of organic molecules for customizable ter  aSan Francisco, CAbSPIE-Int Soc Optical Engineering, 1000 20th ST, PO Box 10, Bellingham, WA 98227-0010 USAcFEB  aArticle Number: UNSP 89850P0 v89853 a<p>Terahertz (THz) frequency band lies between the microwave and infrared region of the electromagnetic spectrum. Molecules having strong resonances in this frequency range are ideal for realizing "Terahertz tags" which can be easily incorporated into various materials. THz spectroscopy of molecules, especially at frequencies below 10 THz, provides valuable information on the low frequency vibrational modes, viz. intermolecular vibrational modes, hydrogen bond stretching, torsional vibrations in several chemical and biological compounds. So far there have been very few attempts to engineer molecules which can demonstrate customizable resonances in the THz frequency region. In this paper, Diamidopyridine (DAP) based molecules are used as a model system to demonstrate engineering of THz resonances (&lt; 10 THz) by fine-tuning the molecular mass and bond strengths. Density Functional Theory (DFT) simulations have been carried out to explain the origin of THz resonances and factors contributing to the shift in resonances due to the addition of various functional groups. The design approach presented here can be easily extended to engineer various organic molecules suitable for THz tags application.</p>1 aRay, Shaumik1 aDash, Jyotirmayee1 aNallappan, Kathirvel1 aKaware, Vaibhav1 aBasutkar, Nitin1 aAmbade, Ashootosh1 aJoshi, Kavita1 aPesala, Bala  uhttps://library.ncl.res.in/content/design-and-engineering-organic-molecules-customizable-terahertz-tags01786nas a2200157   4500008004100000022001400041245006900055210006800124260012500192300002300317490000800340520114900348100002001497700001801517856009301535       2014                        eng d  a0021-960600aScaling up the shape: a novel growth pattern of gallium clusters0 aScaling up the shape a novel growth pattern of gallium clusters  aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScAUG  aArticle No. 0543080 v1413 a<p>Putative global minima for Ga+N clusters with size ``N'' ranging from 49 to 70 are found by employing the Kohn-Sham formulation of the density functional theory, and their evolution is described and discussed in detail. We have discovered a unique growth pattern in these clusters, all of which are hollow core-shell structures. They evolve with size from one spherical core-shell to the next spherical core-shell structure mediated by prolate geometries, with an increase in overall diameter of the core, as well as the shell, without putting on new layers of atoms. We also present a complete picture of bonding in gallium clusters by critically analyzing the molecular orbitals, the electron localization function, and Bader charges. Bonding in these clusters is a mixture of metallic and covalent type that leans towards covalency, accompanied by marginal charge transfer from the surface to the core. Most molecular orbitals of Ga clusters are non-jellium type. Covalency of bonding is supported by a wide localization window of electron localization function, and joining of its basins along the bonds. (C) 2014 AIP Publishing LLC.</p>1 aKaware, Vaibhav1 aJoshi, Kavita  uhttps://library.ncl.res.in/content/scaling-shape-novel-growth-pattern-gallium-clusters-001747nas a2200169   4500008004100000022001400041245007300055210006700128260007100195300001600266490000800282520113200290100001601422700002001438700001801458856010101476       2015                        eng d  a1932-744700aMultifaceted thermodynamics of Pb-n (n=16-24) clusters: a case study0 aMultifaceted thermodynamics of Pbn n1624 clusters a case study  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcOCT  a23698-237070 v1193 a<p>Thermodynamic response of small clusters is a challenging area of exploration, both experimentally and theoretically. In this article, we study the thermodynamic behavior of small Pb clusters (size 16-24) using Born-Oppenheimer molecular dynamics. A new ground state structure is reported for Pb-20. Except for Pb-21, all clusters fragment at temperatures above T-m[bulk] and show no signs of melting. Characteristic behavior like restricted diffusion and solid solid transition is discussed in detail. Variation in the isomerization temperature of these clusters is explained using the bond length analysis. Root mean square bond length fluctuations (delta(rms)) along with distribution of atoms about center of mass of the cluster as a function of time and distance-energy (DE) plots are used to bring out the essential features of Pb cluster thermodynamics. Analysis carried out using these parameters, and their interpretation regarding state of the system, are discussed in detail. We highlight that it is not possible to define ``liquid state'' for these small clusters, in the conventional frame of understanding.</p>1 aSusan, Anju1 aKaware, Vaibhav1 aJoshi, Kavita  uhttps://library.ncl.res.in/content/multifaceted-thermodynamics-pb-n-n16-24-clusters-case-study-101039nas a2200121   4500008004100000245005700041210005700098260000800155520062700163100002000790700001800810856008900828       2015                        eng d00aPartial ionic bonding in homogeneous sodium clusters0 aPartial ionic bonding in homogeneous sodium clusters  cAPR3 a<p>In this work, we report an interesting observation of partial ionic bonding due to charge transfer in homogeneous sodium clusters. The charge transfer causes the electronic charge to accumulate on the surface, and the resulting charges on atoms range between +0.4 to -1.0 |e^-|. We also demonstrate that this disparity among effective charges on atoms is geometry dependent, such that atoms experiencing similar surrounding, have equal effective charge. It is speculated that this phenomenon will occur among other homogeneous clusters as well, and its extent will be defined by the valence electron delocalization.</p>1 aKaware, Vaibhav1 aJoshi, Kavita  uhttps://library.ncl.res.in/content/partial-ionic-bonding-homogeneous-sodium-clusters02541nas a2200229   4500008004100000022001400041245013000055210006900185260011000254300001600364490000600380520161200386100002801998700002002026700002302046700002202069700002302091700001802114700002602132700002402158856012902182       2015                        eng d  a2046-206900aPt-nanoparticle functionalized carbon nano-onions for ultra-high energy supercapacitors and enhanced field emission behaviour0 aPtnanoparticle functionalized carbon nanoonions for ultrahigh en  aTHOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLANDbROYAL SOC CHEMISTRYcSEP  a80990-809970 v53 a<p>In the present work, we have investigated the charge storage capacitive response and field emission behaviour of platinum (Pt) nanoparticles decorated on carbon nano onions (CNOs) and compared them with those of pristine carbon nano onions. The specific capacitance observed for Pt-CNOs is 342.5 F g(-1), about six times higher than that of pristine CNOs, at a scan rate of 100 mV s(-1). The decoration with Pt nanoparticles, without any binder or polymer separator on the CNO, leading to enhanced supercapacitance is due to easy accessibility of Na2SO4 electrolyte in the active material. The Density Functional Theory (DFT) calculations of these systems reveal enhancement in the Density of States (DOS) near the Fermi energy (E-F) on account of platinum decoration on the CNOs. Furthermore, the field emission current density of similar to 0.63 mA cm(-2) has been achieved from the Pt-CNOs emitter at an applied electric field of similar to 4.5 V mu m(-1) and from the pristine CNOs sample current density of similar to 0.4 mA cm(-2) has been achieved at an applied electric field of similar to 6.6 V mu m(-1). The observed enhanced field emission behavior has been attributed to the improved electrical conductivity and increased emitting sites of the Pt-CNO emitter. The field emission current stability of the Pt-CNO emitter over a longer duration is found to be good. The observed results imply multifunctional potential of Pt-CNOs, as supercapacitor material in various next generation hybrid energy storage devices, and field emitters for next generation vacuum nano/microelectronic devices.</p>1 aSuryawanshi, Sachin, R.1 aKaware, Vaibhav1 aChakravarty, Disha1 aWalke, Pravin, S.1 aMore, Mahendra, A.1 aJoshi, Kavita1 aRout, Chandra, Sekhar1 aLate, Dattatray, J.  uhttps://library.ncl.res.in/content/pt-nanoparticle-functionalized-carbon-nano-onions-ultra-high-energy-supercapacitors-and-002651nas a2200241   4500008004100000022001400041245011100055210006900166260007100235300001400306490000800320520176800328100002202096700001802118700002502136700002002161700002402181700002402205700002602229700001802255700001702273856011902290       2015                        eng d  a1089-563900aTerahertz spectroscopy and solid-state density functional theory calculations of cyanobenzaldehyde isomers0 aTerahertz spectroscopy and solidstate density functional theory   a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcJUL  a7991-79990 v1193 a<p>Spectral signatures in the terahertz (THz) frequency region are mainly due to bulk vibrations of the molecules. These resonances are highly sensitive to the relative position of atoms in a molecule as well as the crystal packing arrangement. To understand the variation of THz resonances, THz spectra (2-10 THz) of three structural isomers: 2-, 3-, and 4-cyanobenzaldehyde have been studied. THz spectra obtained from Fourier transform infrared (FTIR) spectrometry of these isomers show that the resonances are distinctly different especially below 5 THz. For understanding the intermolecular interactions due to hydrogen bonds, four molecule cluster simulations of each of the isomers have been carried out using the B3LYP density functional with the 6-31G(d,p) basis set in Gaussian09 software and the compliance constants are obtained. However, to understand the exact reason behind the observed resonances, simulation of each isomer considering the full crystal structure is essential. The crystal structure of each isomer has been determined using X-ray diffraction (XRD) analysis for carrying out crystal structure simulations. Density functional theory (DFT) simulations using CRYSTAL14 software, utilizing the hybrid density functional B3LYP, have been carried out to understand the vibrational modes. The bond lengths and bond angles from the optimized structures are compared with the XRD results in terms of root-mean-square-deviation (RMSD) values. Very low RMSD values confirm the overall accuracy of the results. The simulations are able to predict most of the spectral features exhibited by the isomers. The results show that low frequency modes (&lt;3 THz) are mediated through hydrogen bonds and are dominated by intermolecular vibrations.</p>1 aDash, Jyotirmayee1 aRay, Shaurnik1 aNallappan, Kathirvel1 aKaware, Vaibhav1 aBasutkar, Nitin, B.1 aGonnade, Rajesh, G.1 aAmbade, Ashootosh, V.1 aJoshi, Kavita1 aPesala, Bala  uhttps://library.ncl.res.in/content/terahertz-spectroscopy-and-solid-state-density-functional-theory-calculations-0