Electronic Structure Principles Research Articles

Formaldehyde decomposition through profiles of global reactivity indices

Variation of global reactivity descriptors along the two different pathways for formaldehyde decomposition has been investigated in order to analyze the validity of various electronic structure principles of density functional theory. Calculated energetics and geometrical parameters are in good agreement with the previous investigations. The hardness and electrophilicity are, respectively, found to be a pointer of the most stable and the most reactive identity in most cases. Profiles of these quantities, as a function of the reaction coordinates narrate the dependability of the descriptors. The difference in the global reactivity descriptors between a symmetric reaction and a non-symmetrical reaction along the reaction coordinate in the same decomposition pathway has also been analyzed. Our investigation provides useful exploratory guidelines towards the foundation of chemical reactivity descriptors.

Chemical Reactivity Dynamics and Quantum Chaos in Highly Excited Hydrogen Atoms in an External Field: A Quantum Potential Approach

Dynamical behavior of chemical reactivity indices like electronegativity, hardness, polarizability, electrophilicity and nucleophilicity indices is studied within a quantum fluid density functional framework for the interactions of a hydrogen atom in its ground electronic state (n = 1) and an excited electronic state (n = 20) with monochromatic and bichromatic laser pulses. Time dependent analogues of various electronic structure principles like the principles of electronegativity equalization, maximum hardness, minimum polarizability and maximum entropy have been found to be operative. Insights into the variation of intensities of the generated higher order harmonics on the color of the external laser field are obtained. The quantum signature of chaos in hydrogen atom has been studied using a quantum theory of motion and quantum fluid dynamics. A hydrogen atom in the electronic ground state (n = 1) and in an excited electronic state ( n = 20) behaves differently when placed in external oscillating monochromatic and bichromatic electric fields. Temporal evolutions of Shannon entropy, quantum Lyapunov exponent and Kolmogorov – Sinai entropy defined in terms of the distance between two initially close Bohmian trajectories for these two cases show marked differences. It appears that a larger uncertainty product and a smaller hardness value signal a chaotic behavior.

Electronic Structure Principles and Atomic Shell Structure

Hardness and polarizability are associated with easily discernible atomic shell structures across the periodic table. In a given period the noble gas atom is the hardest and the least polarizable, as expected from its exceptional stability vis-a-vis the principles of maximum hardness and minimum polarizability. The electrophilicity index also exhibits periodicity.

Reactivity Dynamics in Atom−Field Interactions: A Quantum Fluid Density Functional Study

Dynamical behavior of chemical reactivity indices like electronegativity, hardness, polarizability, entropy, electrophilicity and nucleophilicity indices and uncertainty product is studied within a quantum fluid density functional framework for the interactions of a helium atom in its ground and excited electronic states with monochromatic and bichromatic laser pulses with different intensities. Time dependent analogues of various electronic structure principles like the principles of electronegativity equalization, maximum hardness, minimum polarizability and maximum entropy have been found to be operative. Insights into the variation of intensities of the generated higher order harmonics on the color and intensity of the external laser field are obtained.

A Density Functional Treatment of Chemical Reactivity and the Associated Electronic Structure Principles in the Excited Electronic States

Global reactivity parameters like the softness and the polarizability and local reactivity parameters like the Fukui function and the local hardness have been calculated for the ground (1S) and several excited electronic states (1P, 1D, 1F) of various helium isoelectronic systems (He, Li+, Be2+, B3+, C4+). Only the lowest energy state of a given symmetry is chosen because of the validity of the excited state density functional theory exclusively for this type of states. The softness varies linearly with the cube root of the polarizability for both the ground and the excited states. It has been demonstrated for the first time for the systems studied that a system is harder and less polarizable in its ground state than in any of its excited states. Radial distributions of the charge density, the Fukui function, and the local hardness exhibit characteristic shell structures in both the ground and the excited states.