Browsing by Author "Chattaraj, PK"

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    Molecular electronic excitations and the minimum polarizability principle
    (2000) Fuentealba, P; Simón-Manso, Y; Chattaraj, PK
    The validity of the minimum polarizability principle upon electronic excitation is studied as a companion principle of that obtained by Chattaraj and Poddar in the case of the maximum hardness principle. Twelve diatomic molecules have been selected and, both the hardness and the dipole polarizability for the ground and excited states have been calculated by means of ab initio density functional calculations using Sadlej's basis set. It has been found that a molecule is less polarizable in its ground state than in an electronically excited state of the same spin multiplicity.
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    Towards understanding the molecular internal rotations and vibrations and chemical reactions through the profiles of reactivity and selectivity indices: an ab initio SCF and DFT study
    (TAYLOR & FRANCIS LTD, 2003) Chattaraj, PK; Gutierrez Oliva, S; Jaque, P; Toro Labbe, A
    Ab initio SCF and DFT(B3LYP) calculations are performed with 6-311G** basis sets for obtaining insights into molecular internal rotations in HXNX (X=O,S), different vibrational modes in water and double proton transfer reaction in (HONO)(2). While chemical reactivity is analyzed in terms of the pro. le of the global reactivity parameters, such as energy, chemical potential, hardness, polarizability, molecular valency and electrophilicity indices, the site selectivity is understood through the variations in local descriptors, such as the Fukui function and atomic valency. Principles of maximum hardness and molecular valency and the minimum polarizability principle are found to be valid in almost all cases. Rotational isomerization reactions can be better characterized by making use of the maximum hardness principle along with Hammond's postulate. Extremum points in electrophilicity during internal rotations, vibrations and chemical reaction can be located from those of chemical potential and hardness. The Fukui function and atomic valency show inverse behaviour in most cases.
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    Validity of the minimum polarizability principle in molecular vibrations and internal rotations: An ab initio SCF study
    (AMER CHEMICAL SOC, 1999) Chattaraj, PK; Fuentealba, P; Jaque, P; Toro Labbe, A
    Molecular vibrations in ammonia (NH3) and hydrogen sulfide (H2S), and internal rotations in hydrogen peroxide (HOOH), hydrogen thioperoxide (HSOH), hydrogen persulfide (HSSH), and ethylene (C2H4) are studied using ab initio SCF methods at the Hartree-Fock level using:a-standard Pople 6-311G** basis set. Polarizability values are calculated using both Pople's and Sadlej's basis sets, Any nontotally symmetric distortion in bond length or bond angle along the vibrational symmetry coordinates of a molecule around its equilibrium geometry decreases the equilibrium hardness value and increases the:equilibrium polarizability value, During rotational isomerization the minimum energy conformation corresponds to the maximum hardness and minimum polarizability values and the maximum energy conformation corresponds to the minimum hardness and maximum polarizability values, Density functional calculations confirm these observed trends, In general we have found that the conditions of maximum hardness and minimum polarizability complement the minimum energy criterion for molecular stability.