Articles written in Journal of Chemical Sciences

    • Stationary coupled cluster response: Role of cubic terms in molecular properties

      Nayana Vaval Keya Ghose Priya Nair Sourav Pal

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      We have demonstrated an application of a stationary coupled cluster response approach for molecular properties using an Euler functional. This involves terms which are of cubic power in cluster amplitudes. We have shown that these are important terms and have also discussed the convergence properties of the functional for higher order properties.

    • Molecular orbital calculations on [HRu3(CO)9(PhNCO)] and related clusters

      Sumit Bhaduri Abhijit Chatterjee Sourav Pal Shilpa Tawde Doble Mukesh

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      Molecular orbital calculations (EHMO) have been performed on five ruthenium carbonyl clusters considered to be involved in the reductive carbonylation of nitrobenzene. The bonding in the isocyanate cluster, [HRu3(CO)9(HNCO)], is shown to arise mainly from the interaction between the LUMO of HNCO and HOMO of the [HRu3(CO)9] fragment. The relative stabilities of this cluster, two of its isomers and the CO-eliminated cluster [HRu3(CO)9(HN)], are also commented upon. The calculated results are in accordance with empirical kinetic data.

    • Separability of local reactivity descriptors

      Akhilesh Tanwar Sourav Pal

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      The size-dependence of different local reactivity descriptors of dimer A2 and AB type of systems is discussed. We derive analytic results of these descriptors calculated using finite difference approximation. In particular, we studied Fukui functions, relative electrophilicity and relative nucleophilicity, local softness and local philicity. The results are explained using the example of the dimer of BH3NH3.

    • Foreword

      Sourav Pal P Venuvanalingam

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    • Reactivity descriptors and electron density analysis for ligand chemistry: A case study of 2,2'-bipyridine and its analogues

      Bhakti S Kulkarni Akhilesh Tanwar Sourav Pal

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      In this paper, we study the reactivity of diimines like 2,2'-bipyridine and its analogues using reactivity descriptors. We discuss evaluation of local descriptors using relaxed as well as frozen approximation and characterize the 𝜎/𝜋 acceptance/donor characteristics of the above ligands. The intermolecular reactivity sequence for the same systems is examined by the global and local philicity index. In addition, electron density analysis has been carried out to highlight the possible strengths of interaction of the bipyridine and its analogues with metal ions.

    • Fock-space multi-reference coupled-cluster response with the effect of triples on dipole moment of ClO and SF radicals

      Lalitha Ravichandran Debarati Bhattacharya Nayana Vaval Sourav Pal

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      Dipole moment calculations of SF and ClO radicals have been carried out using the recently developed partial triples correction to Fock-space multi-reference coupled cluster method. Theoretical calculation of the doublet SF and ClO radicals is useful due to their importance in atmospheric chemistry. The dipole moments of these radicals are extremely sensitive to correlation effects. A brief insight to the way the triples correction has been implemented is presented. We compare the results obtained from our analytic response treatment with that of restricted open Hartree-Fock (ROHF) calculations. Results are presented for both relaxed and non-relaxed approach in the ROHF method. Results suggest the importance of triples corrections. The effects of orbital relaxation are also analysed from the results.

    • Role of substituents on the reactivity and electron density profile of diimine ligands: A density functional theory based study

      Bhakti S Kulkarni Deepti Mishra Sourav Pal

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      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 𝜎-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.

    • Calculation of hyperfine structure constants of small molecules using Z-vector method in the relativistic coupled-cluster framework


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      The Z-vector method in the relativistic coupled-cluster framework is employed to calculate the parallel and perpendicular components of the magnetic hyperfine structure constant of a few small alkaline earth hydrides (BeH, MgH, and CaH) and fluorides (MgF and CaF). We have compared our Z-vector results with the values calculated by the extended coupled-cluster (ECC) method reported in Phys. Rev. A 91 022512 (2015). All these results are compared with the available experimental values. The Z-vector results are found to be in better agreement with the experimental values than those of the ECC values.

    • Role of molecular modelling in the development of metal-organic framework for gas adsorption applications


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      More than 47,000 articles have been published in the area of Metal-Organic Framework since itsseminal discovery in 1995, exemplifying the intense research carried out in this short span of time. Among other applications, gas adsorption and storage are perceived as central to the MOFs research, and more than 10,000 MOFs structures are reported to date to utilize them for various gas storage/separation applications.Molecular modeling, particularly based on density functional theory, played a key role in (i) understanding the nature of interactions between the gas and the MOFs geometry (ii) establishing various binding pockets and relative binding energies, and (iii) offering design clues to improve the gas uptake capacity of existing MOF architectures. In this review, we have looked at various MOFs that are studied thoroughly using DFT/periodic DFT (pDFT) methods for CO2, H2, O2, and CH4 gases to provide a birds-eye-view on how various exchange-correlation functionals perform in estimating the binding energy for various gases and how factors such as nature of the (i) metal ion, (ii) linkers, (iii) ligand, (iv) spin state and (v) spin-couplings play a role in this process with selected examples. While there is still room for improvement, the rewards offered by the molecular modelling of MOFs were already substantial that we advocate experimental and theoretical studies to go hand-in-hand to undercut the trial-and-error approach that is often perceived in the selection of MOFs and gas partners in this area.

      The importance of density functional theory-based molecular modeling studies in offering design clues to improve the gas adsorption and storage capacity of existing MOF architectures is discussed here. The use of DFT-based investigation in conjunction with experimental synthesis is an imperative tool in designing new-generation MOFs with enhanced uptake capacity.

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