01408nas a2200181 4500008004100000022001400041245008000055210006900135260012500204300001100329490000800340520068800348100001801036700001601054700001901070700002301089856011401112 2007 eng d a0021-960600aElectronic structure of spherical quantum dots using coupled cluster method0 aElectronic structure of spherical quantum dots using coupled clu aCIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USAbAMER INST PHYSICScSEP a1147080 v1273 a

2, 6, 12, and 20 electron quantum dots have been studied using coupled cluster at singles and doubles level and extensive multireference coupled cluster (MRCC) method. A Fock-space version of MRCC (FSMRCC) containing single hole-particle excited determinants has been used to calculate low-lying excited states of the above system. The ionization potential and electron affinity are also calculated. The effect of correlation energy on excitation energy and charge density is shown by calculating them at the high density region (low value of density parameter r(s)) and at the low density region (high value of density parameter r(s)). (c) 2007 American Institute of Physics.

1 aHeidari, Ideh1 aPal, Sourav1 aPujari, B., S.1 aKanhere, Dilip, G. uhttps://library.ncl.res.in/content/electronic-structure-spherical-quantum-dots-using-coupled-cluster-method-001640nas a2200193 4500008004100000022001400041245013400055210006900189260007100258300001400329490000800343520086800351100001901219700002501238700002301263700002001286700001601306856012401322 2008 eng d a1520-610600aComparative study of structural, acidic and hydrophilic properties of Sn-BEA with Ti-BEA using periodic density functional theory0 aComparative study of structural acidic and hydrophilic propertie a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcMAR a2573-25790 v1123 a

Periodic density functional theory has been employed to characterize the differences in the structural, Lewis acidic and hydrophilic properties of Sn-BEA and Ti-BEA. We show that the incorporation of Sri increases the Lewis acidity of BEA compared to the incorporation of Ti. Hence, the present work gives insight into the role of Sn in increasing the efficiency of the oxidation reactions. The results also justify that the percentage of Sri substituted in BEA is less than Ti. The structural analysis shows that the first coordination shell of Sri is larger than that of Ti. However, the second coordination of both sites remains the same. The water adsorption properties of these substituted zeolites are quantified. Moreover, we explain the higher Lewis acidity of Sn than the Ti site on the basis of the Fukui functions and charge population analysis.

1 aShetty, Sharan1 aKulkarni, Bhakti, S.1 aKanhere, Dilip, G.1 aGoursot, Annick1 aPal, Sourav uhttps://library.ncl.res.in/content/comparative-study-structural-acidic-and-hydrophilic-properties-sn-bea-ti-bea-using-002127nas a2200229 4500008004100000022001400041245013700055210006900192260007700261300001200338490000600350520124500356653001901601653003601620653001301656653002101669653001901690100001901709700001601728700002301744856013001767 2008 eng d a1439-423500aDensity functional investigations of electronics structure and dehydrogenation reactions of Al- and Si-substituted magnesium hydride0 aDensity functional investigations of electronics structure and d aPO BOX 10 11 61, D-69451 WEINHEIM, GERMANYbWILEY-V C H VERLAG GMBHcAPR a928-9340 v93 a

{The effect on the hydrogen storage attributes of magnesium hydride (MgH2) of the substitution of Mg by varying fractions of Al and Si is investigated by an ab initio plane-wave pseuodopotential method based on density functional theory. Three supercells, namely, 2 x 2 x x 3 x 1 x 1 and 5 x 1 x 1 are used for generating configurations with varying amounts (fractions x=0.0625, 0.1, and 0.167) of impurities. The analyses of band structure and density of states (DOS) show that, when a Mg atom is replaced by Al, the band gap vanishes as the extra electron occupies the conduction band minimum. In the case of Si-substitution, additional states are generated within the band gap of pure MgH2-significontly reducing the gap in the process. The reduced band gaps cause the Mg-H bond to become more susceptible to dissociation. For all the fractions, the calculated reaction energies for the stepwise removal of H-2 molecules from Al- and Si-substituted MgH2 ore much lower than for H-2 removal from pure MgH2. The reduced stability is also reflected in the comparatively smaller heats of formation (Delta H-f) of the substituted MgH2 systems. Si causes greater destabilization of MgH2 than Al for each x. For fractions x = 0.167 of Al

10aband structure10aDensity functional calculations10ahydrides10aHydrogen storage10aThermodynamics1 aKelkar, Tuhina1 aPal, Sourav1 aKanhere, Dilip, G. uhttps://library.ncl.res.in/content/density-functional-investigations-electronics-structure-and-dehydrogenation-reactions-al-002881nas a2200229 4500008004100000022001400041245012700055210006900182260007300251300001200324490000700336520200400343653002202347653002102369653002102390653002202411653002902433100001902462700002302481700001602504856013102520 2008 eng d a0927-025600aFirst principles calculations of thermal, equations of state and thermodynamical properties of MgH2 at finite temperatures0 aFirst principles calculations of thermal equations of state and  aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcMAY a510-5160 v423 a

We present the first principles calculations of the thermodynamical properties of magnesium hydride (MgH2) over a temperature range of 0-1000 K. The phonon dispersions are determined within the density functional framework and are used to calculate the free energy of MgH2 within the quasiharmonic approximation (QHA) at each cell volume and temperature T. Using the free energies the thermal equation of state (EOS) is derived at several temperatures. From the thermal EOS structural parameters such as the equilibrium bell volume (V-0) and elastic properties, namely, bulk modulus (K-0) and its pressure derivative (K-0(')) are computed. The free energies are also used to calculate various thermodynamical properties within QHA. These include internal energy E, entropy S, specific heat capacity at constant pressure C-P, thermal pressure P-thermal(V,T) and volume thermal expansion Delta V/V (%). The good agreement of calculated values of S and Cp with experimental data exhibits that QHA can be used as a tool for calculating the thermodynamical properties of MgH2 over a wide temperature range. P-thermal(V,T) increases strongly with T at all the volumes but it is a slowly varying function of volume for T = 298-500 K. According to Karki [B.B. Karki, Am. Miner. 85 (2000) 1447] such volume based variations can be neglected and so it is possible to estimate the thermal EOS only with the knowledge of the measured P-thermal(V,T) versus temperature at ambient pressure and isothermal compression data at ambient temperature. Temperature dependence of Delta V/V(%) shows that V-0 increased with increase in temperature. However, the percentage decrease in K-0 superseded this percentage increase in V-0 even at temperatures moderately higher than 298 K. Therefore, we suggest application of temperature (T > 298 K) as an approach to enhance the hydrogen storage capacity of MgH2 because of its better compressibility at these temperatures. (C) 2007 Elsevier B.V. All rights reserved.

10aequation of state10aHydrogen storage10alattice dynamics10amagnesium hydride10aThermodynamic properties1 aKelkar, Tuhina1 aKanhere, Dilip, G.1 aPal, Sourav uhttps://library.ncl.res.in/content/first-principles-calculations-thermal-equations-state-and-thermodynamical-properties-mgh2-001835nas a2200193 4500008004100000022001400041245009700055210006900152260007100221300001600292490000800308520110200316100001801418700001501436700001801451700002201469700002301491856012701514 2011 eng d a1089-563900aGrowth and structural properties of Mg-N (N=10-56) clusters: density functional theory study0 aGrowth and structural properties of MgN N1056 clusters density f a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcNOV a12307-123140 v1153 a

Using the minima hopping global geometry optimization method on density functional potential energy surface, we have studied the structural and electronic properties of magnesium clusters for a size range of Mg-N where N = 10-56. Our exhaustive search reveals that most of our global minima are nonsymmetric in the size range above N = 20. We elucidate the evolutionary trend of the entire series and present more details about the peculiar growth of the clusters. For N> 20, it is possible to divide the cluster into two regions: the core region and the surface region. It turns out that the growth follows a peculiar cyclic pattern where the core and surface grow alternatively. The surface energy, as a function of number of atoms shows a clear signature as the number of atoms in the core increases by one. We have also carried out stability analysis and the stable sizes(magic numbers) agree very well with the experimental magic numbers reported by Diederich [J. Chem. Phys. 2011, 134, 124302]. We point out the similarities and differences between our results and sodium clusters.

1 aHeidari, Ideh1 aDe, Sandip1 aGhazi, S., M.1 aGoedecker, Stefan1 aKanhere, Dilip, G. uhttps://library.ncl.res.in/content/growth-and-structural-properties-mg-n-n10-56-clusters-density-functional-theory-study-001375nas a2200181 4500008004100000022001400041245009200055210006900147260007300216300001200289490000800301520068400309100001800993700001801011700001601029700002301045856012501068 2013 eng d a0009-261400aPolarizability of few electron quantum dots: extended coupled-cluster response approach0 aPolarizability of few electron quantum dots extended coupledclus aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJAN a263-2670 v5553 a

The dipole polarizability is studied for few electron quantum dots using extended coupled cluster linear response method (ECCLR). The polarizability of pure parabolic quantum dots depends only on the number of electrons and the parabolic confinement strength. We added impurity in a GAUSSIAN form to the external parabolic potential and used ECCLR to calculate polarizability. To examine the effect of external potential, we changed the parabolic confinement to square-well and repeated all calculations. We mainly looked at eigenvalue spectrum and charge density specially when the system shifts towards lower density regions. (C) 2012 Elsevier B. V. All rights reserved.

1 aHeidari, Ideh1 aVaval, Nayana1 aPal, Sourav1 aKanhere, Dilip, G. uhttps://library.ncl.res.in/content/polarizability-few-electron-quantum-dots-extended-coupled-cluster-response-approach-0