An approximated hardness kernel, which includes the second derivative with respect to the density of the kinetic energy, the electron-electron coulomb repulsion, and the exchange density functionals, has been tested for the calculation of the global hardness. The results obtained for a series of 40 cations and neutral systems and 16 anions represent in most cases an improvement of the results o...

In this paper we study the small Na+N (N 12) cationic clusters fragmentation channels, with all electronic calculations performed at the B3LYP/6–311G+(d,p) DFT level of theory. For these cluster sizes, we obtain for all neutral, cationic, bi-cationic and anionic species the optimized geometries, total energies and electronic properties such as the adiabatic ionization potentials, electron affin...

Global optimization process can often be divided into two subprocesses: exploration and exploitation. The tradeoff between exploration and exploitation (T:Er&Ei) is crucial in search and optimization, having a great effect on global optimization performance, e.g., accuracy and convergence speed of optimization algorithms. In this paper, definitions of exploration and exploitation are first give...

In a very recent article (Torrent-Sucarrat et al., J Comput Chem 2007, 28, 574), we have shown how to evaluate the global hardness for polyatomic molecules using a hardness kernel approximation. We present here an extension of this previous work by improving the model used to evaluate the hardness kernel and the Fukui function. In addition, the concept of the local hardness is analyzed in detai...

A simplified model of the hardness kernel, hð~r ; ~r 0Þydð~r K~r 0Þ, has been evaluated for the calculation of the global hardness in a series of Lewis acids and bases using the MP2 method. It is found that this simple model yields the appropriate ordering of the molecules according to their hardness values when compared to experimental available results. q 2005 Elsevier B.V. All rights reserved.

rivers are one of the most valuable aquatic ecosystems that their physiochemical properties and the biology of their organisms have strong interactions. one of the major rivers in iran, which covers a variety of ecosystems, is called tajan river. in this research, the effect of different pollution sources on water quality of this water body was investigated. samples were collected in seven diff...

The protonation mechanism of pyrrole is investigated in terms of various global and regional (fragment) hardness (softness) parameters and related quantities in order to identify the most sensitive criteria indicating the lmown o.-preference for electrophilic substitution in this molecule. Both rigid and relaxed hardness data are discussed. Numerical results for the H+... pyrrole system, obtain...

Finding a proper local measure of chemical hardness has been a long-standing aim of density functional theory. The traditional approach to defining a local hardness index, by the derivative of the chemical potential l with respect to the electron density nðr *Þ subject to the constraint of a fixed external potential vðr *Þ, has raised several questions, and its chemical applicability has proved...

In this research, the interactions of HCN gas with pristine, Ga-, N- and GaN-doped of boron phosphide nanotube (BPNTs) were investigated by using density function theory (DFT). The structure, electrical and NQR parameters, quantum descriptors involving energy gap, global hardness, global softness, electrophilicity, electronic chemical potential and electronegativity were calculated. The adsorpt...