Chemical potential and hardness for open shell radicals: model for the corresponding anions

In this article, we have obtained theoretical values of chemical potential and hardness for open shell free radicals using a wave function approach. The calculated values of the hardness are useful particularly for rank ordering of the corresponding anions. A ΔSCF procedure is used to obtain these values, and the results are compared with corresponding experimental values. The procedure also leads us to the reliability of the ΔSCF procedure for these quantities

On non-negativity of Fukui function indices

In this paper we have analyzed the factors which cause Fukui function (FF) indices to be negative, when evaluated in condensed form through crude finite difference approximation. Inability to take care of the relaxation effect and improper charge partitioning techniques have been cited to be the probable reasons. For the first time, we have shown that the "stockholders"charge partitioning technique (i.e., Hirshfeld's analysis) produces non-negative FF values which, when evaluated through other kinds of charge partitioning techniques, become negative in some cases. Advantages of "stockholders"charge partitioning over other kinds of partitioning techniques are also discussed, particularly in case of evaluation of condensed FF

On non-negativity of Fukui function indices. II

In this article we have tried to critically analyze the factors which cause the condensed Fukui function (FF) indices [f(r)] to attain a negative value in some cases. The evaluation of condensed FF indices needs finite-difference approximation to the electronic charge densities, and the finite-difference approximation needs partitioning of the electronic charge to the constituent atoms. In a previous article [J. Chem. Phys. 110, 8236 (1999)] we have argued that the probable factors, which cause the FF indices to appear negative in some cases, may be (i) the improper charge partitioning techniques adopted to evaluate f(r); (ii) large change in the electron number (ΔN = 1) when f(r) is evaluated in condensed form using the finite-difference approximation. In this article we want to focus more on the first factor. The present study shows through pictorial as well as numerical demonstrations of the charge-density difference [ρneutral(f)-ρcation(f) and ρanion(f)-ρneutral(f)] plots, how the negative condensed FF value appears with the use of improper charge partitioning and how the use of Hirshfeld partitioning can solve this problem

Hardness as a function of polarizability in a reaction profile

In this article, for the first time, we have correlated chemical hardness with polarizability when a single bond in a complex polyatomic molecule is distorted. A predominantly linear relation has been observed between the cube root of polarizability and hardness when various types of bonds are distorted. The molecules CH3Cl, CH3F and CH4 are chosen as typical example systems

Interaction between Small Gold Clusters and Nucleobases: A Density Functional Reactivity Theory Based Study

The thermodynamic and kinetic aspects associated with the interaction of small gold clusters (Au_<i>n</i>, where <i>n</i> = 3–6) with nucleobases are assessed using a density functional reactivity theory based comprehensive decomposition analysis of stabilization energy scheme. It is observed that the trend of interaction between Au_<i>n</i> clusters and nucleobases follows the order G > A > C > T > U. Also, the Watson–Crick base pair GC interacts with Au_<i>n</i> clusters more preferably than that of the AT pair. The observed trend is further supported by conventional binding energy and transition-state calculations at B3PW91 and MP2 levels

Understanding the Interaction of Nucleobases with Chiral Semiconducting Single-Walled Carbon Nanotubes: An Alternative Theoretical Approach Based on Density Functional Reactivity Theory

The present study describes an alternative and computationally cost-effective theoretical approach to explore the interaction of nucleobases with different semiconducting chiral single-walled carbon nanotubes (SWCNTs). Implementing density functional reactivity theory (DFRT) based CDASE (comprehensive decomposition analysis of stabilization energy, Bagaria et al.<i> Phys. Chem. Chem. Phys.</i> <b>2009</b>, <i>11</i>, 8306), scheme kinetic and thermodynamic aspects of the interaction between different DNA bases as well as Watson–Crick base pairs (AT and GC) with SWCNTs are investigated and that is also without performing computationally intensive transition state optimization or thermochemistry calculation. The trend of interaction generated by reactivity parameters (based on the CDASE scheme) follows the experimentally as well as theoretically verified order, G⟩A⟩T⟩C⟩U, observed earlier. Conventional binding energy calculations on some of the chosen systems using the ONIOM QM:MM approach generate a reasonably satisfactory trend of interaction. Reported theoretical findings can be exploited as an alternative (albeit qualitative but rapid) technique to understand the functionalization of CNTs with DNA bases