01640nas 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-002759nas a2200229 4500008004100000022001400041245008300055210006900138260007300207300000800280490000800288520196600296653001002262653001602272653002402288653000802312653002202320100002702342700002502369700001602394856011902410 2009 eng d a0022-286000aBond length variations: electron number profiles and transferable atomic sizes0 aBond length variations electron number profiles and transferable aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcNOV a1-80 v9363 a

A profile of the number of electrons with distance along the M-X bond in gas-phase diatomic molecules has been obtained from electron density plots calculated using DFT B3LYP 6-311G** method for some representative molecules. This ``number profile'' is compared with that expected from the partitioning of the 1D bond-distance into atom-specific transferable ``hub'' or core atomic sizes of the M and X atoms and another ``axle'' size which is associated with a pair of (bonding) electrons. The ``hub'' size is proportional to a core atom-specific size, r(nZ)(c) with r(nZ)(c)(M) >= r(nZ)(c)(X). For ``single bonds'', the ``hub'' size for M atom is C(M)r(nZ)(c)(M) and for X atom is C(X)r(nZ)(c)(X). The ``axle'' size, DMX, is usually the ordinary (similar to 4a(H)/3 where a(H) is the Bohr radius of the hydrogen atom) or elongated (similar to 2a(H)) bond length of the hydrogen molecule. The ``hub'' and ``axle'' sizes could be characterized ``charge-transfer'' (C(M) = pi(2/3) = 2.144; C(X) = pi(4/3)/2 = 2.300 and D(MX) = 4a(H)/3) or ``neutral'' (CM or C(X) = 1, 2, ... and D(MX) = 2a(H)). We use a new ``static'' or ``peripatetic'' classification for the core sizes which is derived from a new condition for metallization in elements based on atomic size. The charge-transfer distance, d(MX)(+/-), is usually found for ``static'' conditions while the ``neutral'' description is usually found when X = F or for ``peripatetic'' conditions. Such a partitioning is seen to agree with that from the plot of the total number of electrons, N(el), vs r along a bond axis. The Nel vs r plots from each atom are described by a simple hydrogen-atom-like function which differ away (''out'') or towards (''in'') the M-X bond. Thus N(in,out)(M, X) = (Z(M,X) +/- 1) exp (-r/B(in,out)) where the minus sign is associated with M and plus sign with X and Bin, out being related inversely to the Slater orbital exponent. (C) 2009 Elsevier B.V. All rights reserved.

10aB3LYP10aBond length10aBond-stretch isomer10aDFT10aDiatomic molecule1 aGanguly, Parthasarathy1 aKulkarni, Bhakti, S.1 aPal, Sourav uhttps://library.ncl.res.in/content/bond-length-variations-electron-number-profiles-and-transferable-atomic-sizes-001450nas a2200169 4500008004100000022001400041245013200055210006900187260007300256300001200329490000800341520073500349100002501084700002601109700001601135856012901151 2010 eng d a0009-261400aInfluence of plane wave cut-off on structural and electronic properties in Sn-BEA and Ti-BEA zeolite water molecule interaction0 aInfluence of plane wave cutoff on structural and electronic prop aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcJAN a374-3790 v4843 a

Periodic systems are best described by the pseudo-potential methods. However, the accuracy of its description depends on the cut-off of plane wave basis. This is much more critical in the case of weak interactions, where a clear understanding on the influence of plane wave cut-off on the structural and electronic properties is not readily available in the literature. In the present work, we have taken a metal substituted beta zeolite-H2O complex for understanding this objective. Our studies show that while a lower cut-off of 500 eV is sufficient for the convergence of the structural parameters, description of energy-dependent properties necessitates a high cut-off value. (C) 2009 Elsevier B.V. All rights reserved.

1 aKulkarni, Bhakti, S.1 aKrishnamurty, Sailaja1 aPal, Sourav uhttps://library.ncl.res.in/content/influence-plane-wave-cut-structural-and-electronic-properties-sn-bea-and-ti-bea-zeolite-002926nas a2200229 4500008004100000022001400041245014300055210006900198260007300267300001000340490000800350520203500358653001702393653001802410653002702428653001702455653002702472100002502499700002602524700001602550856013002566 2010 eng d a1381-116900aProbing lewis acidity and reactivity of Sn- and Ti-beta zeolite using industrially important moieties: a periodic density functional study0 aProbing lewis acidity and reactivity of Sn and Tibeta zeolite us aPO BOX 211, 1000 AE AMSTERDAM, NETHERLANDSbELSEVIER SCIENCE BVcAUG a36-430 v3293 a

The Lewis acidic nature and reactivity of two industrially important catalysts, viz.. Sn and Ti substituted beta zeolite (T-BEA) are analyzed using a unique combination of structural parameters, energetics and reactivity descriptors. To achieve this purpose, we adsorb the industrially important moieties (L) namely NH(3), H(2)O, CH(3)OH, CH(3)CN on the active sites of T-BEA. The calculations were performed using a periodic density functional method where the valence electrons are described using a plane wave basis set in conjunction with pseudo-potentials for the core electrons. The analysis of the structural properties of these complexes reveals that TO(4) shows typical characteristic splitting 120 degrees/90 degrees, close to bipyramidal geometry as compared to tetrahedral symmetry observed in the bare T-BEA. This is associated with small variations in the framework bond lengths (>= 0.08 angstrom) and a substantially large variation of bond angles (<= 10 degrees) in all the ligand-zeolite complexes. Further in both cases of Sn and Ti substituted beta zeolite, ligand interacts at optimum inter-atomic bond distance. Our interaction energies show that adsorption of all ligand moieties is stronger at Sn center than that of Ti. In general, the order of stability of the different T-BEA adducts is NH(3) > H(2)O > CH(3)OH > CH(3)CN. The ligand interaction is associated with the corresponding bond elongation and bond reduction of the adsorbed molecules on catalyst active site, which can be taken as measure of red or blue shifted frequencies. Finally, the global descriptors of reactivity justify the fact that soft acid, Sn-BEA, interacts strongly with soft bases following the Pearson's HSAB principle. However, hard acid, Ti-BEA interacts with soft bases to form a stable Lewis adduct. Furthermore, the HOMO-LUMO gap of all Sn-BEA-L adducts is lower than that of Ti-BEA-L adducts indicating to its higher Lewis acidic nature compared to Ti-BEA. (C) 2010 Elsevier B.V. All rights reserved.

10aBeta zeolite10aLewis acidity10aLigand-zeolite complex10aPeriodic-DFT10aReactivity descriptors1 aKulkarni, Bhakti, S.1 aKrishnamurty, Sailaja1 aPal, Sourav uhttps://library.ncl.res.in/content/probing-lewis-acidity-and-reactivity-sn-and-ti-beta-zeolite-using-industrially-important-001981nas a2200169 4500008004100000022001400041245014900055210006900204260007100273300001600344490000800360520124700368100002501615700002601640700001601666856012901682 2011 eng d a1932-744700aSize- and shape-sensitive reactivity behavior of Al-n(n=2-5, 13, 30, and 100) clusters toward the N-2 molecule: a first-principles investigation0 aSize and shapesensitive reactivity behavior of Alnn25 13 30 and  a1155 16TH ST, NW, WASHINGTON, DC 20036 USAbAMER CHEMICAL SOCcAUG a14615-146230 v1153 a

Reactivity of aluminum clusters has been found to exhibit size-sensitive variations. N-2 reduction is a hard process, and its dissociation on the Al surface is one of the few chemical methods available under nonhazardous conditions. In this context, we attempt to understand the adsorption behavior of N-2 molecules as a function of varying size and shape of Al clusters using a Density Functional Theory (DFT) based method. During the complex formation, various N-2 adsorption modes are examined. The results clearly demonstrate that, while the interaction energy does not vary with respect to the cluster size, shape of the cluster is highly contributive toward the chemisorption (a prerequisite for the reactivity) of the N-2 molecule. The underlying electronic and structural factors influencing the adsorption of N-2 molecules on the Al clusters are analyzed with the help of the Electron Localization Function (ELF) and Frontier Molecular Orbitals. As an illustration, the activation barrier calculations on various Al-13 conformations are calculated, and results confirm the experimental propositions that high-energy structures (depending upon their geometrical and electronic orientation) are more favorable for N-2 reduction.

1 aKulkarni, Bhakti, S.1 aKrishnamurty, Sailaja1 aPal, Sourav uhttps://library.ncl.res.in/content/size-and-shape-sensitive-reactivity-behavior-al-nn2-5-13-30-and-100-clusters-toward-n-2-001813nas a2200253 4500008004100000022001400041245013200055210006900187260010200256300001400358490000800372520087400380653000601254653001901260653000801279653001201287653002701299653002601326653002401352100002501376700001901401700001601420856012301436 2013 eng d a0974-362600aRole of substituents on the reactivity and electron density profile of diimine ligands: a density functional theory based study0 aRole of substituents on the reactivity and electron density prof aC V RAMAN AVENUE, SADASHIVANAGAR, P B \#8005, BANGALORE 560 080, INDIAbINDIAN ACAD SCIENCEScSEP a1247-12580 v1253 a

In this paper, we study the reactivity of diimines like 2, 2(')-bipyridine, 1, l0-phenanthroline and 1, 2, 4-triazines using density-based reactivity descriptors. We discuss the enhancement or diminution in the reactivity of these ligands as a function of two substituent groups, namely methyl (-CH3) group and phenyl (-C6H5) group. The global reactivity descriptors explain the global affinity and philicity of these ligands, whereas the local softness depicts the particular site selectivity. The inter-molecular reactivity trends for the same systems are analysed through the philicity and group philicity indices. The sigma-donor character of these ligands is quantified with the help of electron density profile. In addition, the possible strength of interaction of these ligands with metal ions is supported with actual reaction energies of Ru-L complexes.

10a210a2 `-bipyridine10aDFT10adiimine10aReactivity descriptors10aRu-ligand interaction10asubstituent effects1 aKulkarni, Bhakti, S.1 aMishra, Deepti1 aPal, Sourav uhttps://library.ncl.res.in/content/role-substituents-reactivity-and-electron-density-profile-diimine-ligands-density-0