S P Bhattacharyya
Articles written in Journal of Chemical Sciences
Volume 100 Issue 4 August 1988 pp 293-295 Physical and Theoretical
Volume 100 Issue 6 December 1988 pp 509-517 Physical and Theoretical
The charge-transfer energetics of interactions in a series of closed-shell cation-inert gas pairs is studied by using a model based on the electronegativity equalization principle. These results arc compared with those obtained from SCF calculations carried out at the STO-3G level. A model interaction potential is tested for these systems. The possible effect of an additional electrostatic factor in the charge transfer process is investigated.
Volume 101 Issue 3 June 1989 pp 235-242 Physical and Theoretical
An MCSCF model including the effects of solvent polarization is developed. The model is applied within the limitations of INDO approximations to look into the dominant effects of solvent polarization on the electronic structure in the excited states of a model system (e.g.
Volume 101 Issue 5 October 1989 pp 421-428 Physical and Theoretical
A variant of the orthogonal gradient method of orbital optimization in the INDO-MCSCF framework has been used to study the photochemical decomposition of the HNO molecule into H + NO in the lowest1.3A″ states. A complete geometry optimization has been carried out at all points of the reaction path which appears to be almost barrierless. The one-electron density matrix extracted from the optimized wavefunction at each point has been used to generate the relevant sets of quantum chemical valence parameters. A sharp transition is noted in the N-H bond order and hydrogen free valence index when plotted as functions of rNH. This enables us to locate the transition region easily.
Volume 103 Issue 3 March 1991 pp 265-276
The complementarity of one- and two-photon spectroscopy has been utilised for throwing light on the following problems of chemical interest: (1) Weak interaction between identical chromophores separated by insulating bridges gives rise to split states of different symmetries. Two-photon spectroscopy (TPA), in conjunction with one-photon absorption (OPA), has been used to identify the states and hence to estimate the magnitude of interaction in bimolecules and trimolecules. From the shifts between the one- and the two-photon spectra, the splittings have been estimated. Calculations confirm that the dominant interaction is the through-bond one. (2) The second type of problem is the identification of
Volume 106 Issue 2 April 1994 pp 553-568
A local grid method for modelling real-time quantum dynamical events is formulated. The formulation is straightforward for 1-D systems. For more than one dimension, appeal has to be made to mean-field approximation of the appropriate kind. The simplest mean-field model results in time-dependent Hartree-Fourier grid method. The relationship of the proposed method with some other methods available in the literature is examined. A few examples of numerical applications dealing with (i) the dynamics of dissociation and ionization processes in diatoms and atoms respectively and (ii) tunnelling dynamics in the intramolecular H-atom transfer phenomenon are presented.
Volume 116 Issue 5 September 2004 pp 285-291
A genetic algorithm-based recipe involving minimization of the Rayleigh quotient is proposed for the sequential extraction of eigenvalues and eigenvectors of a real symmetric matrix with and without basis optimization. Important features of the method are analysed, and possible directions of development suggested
Volume 121 Issue 5 September 2009 pp 757-766
The dissociation of a diatomic molecule in low frequency polychromatic fields of moderate intensities is studied. Genetic Algorithm is invoked to search out a set of four optimal non-resonant frequencies ($\omega_1$ - $\omega_4$), intensities ($\epsilon_1$ - $\epsilon_4$) the and phase angles ($\delta_1 - \delta_4$), for achieving a facile photo dissociation. Time-dependent Hellmann-Feynman theorem is used to gain insight into the frequency resolved energy absorption pattern. The ‘quantum phase space’ structures indicate occurrence of bond breaking dynamics akin to the classical one.
Volume 124 Issue 1 January 2012 pp 13-19
The quantum dynamics of intramolecular H-atom transfer in malonaldehyde is investigated with a model two-dimensional Hamiltonian constructed with the help of available