Manoj K. Harbola

Hardnesses from electrostatic potentials

By generalization of a method due to Politzer et al. [J. Chem. Phys. 79, 3859 (1983)], it is demonstrated how the absolute hardness of an electronic system can be determined from the electrostatic potential, as a function of position of the system and its positive and negative ions. It is shown that to good accuracy the hardness is one‐half the electrostatic potential at the covalent radius due to the Fukui function.

Stable negative ions within a local exchange formalism

An orbital generated local exchange potential, obtained as the work done in moving an electron in the electric field of its Fermi hole, is shown to give convergent solutions for negative ions comparable to Hartree-Fock accuracy.

Hydrodynamic approach to time-dependent density functional theory; Response properties of metal clusters

Performing electronic structure calculations for large systems, such as nanoparticles or metal clusters, via orbital based Hartree–Fock or Kohn–Sham theories is computationally demanding. To study such systems, therefore, we have taken recourse to the hydrodynamic approach to time-dependent density-functional theory. In this paper we develop a variation-perturbation method within this theory in terms of the particle and current densities of a system. We then apply this to study the linear and nonlinear response properties of alkali metal clusters within the spherical jellium background model.

Local exchange-correlation potential from the force field of the Fermi-Coulomb hole charge for non-symmetric systems

Abstract It is proposed that for non-symmetrical electronic density systems for which the curl of the electric field due to the Fermi-Coulomb hole charge distribution may not vanish, the local effective many-body potential be obtained as the work done against the irrotational component of this field.

Demonstration of Lenz’s law: Analysis of a magnet falling through a conducting tube

We revisit a recent analysis of the time of fall of a magnet as it slows down while passing through a conducting tube. We complement recent work by considering the effect of the thickness of the tube on the time of fall. The resulting expression gives a more accurate expression for the time of fall.

Exploring foundations of time-independent density functional theory for excited states

Based on the work of Gorling and that of Levy and Nagy, a density-functional formalism for many fermionic excited states is explored through a careful and rigorous analysis of the excited-state density to external potential mapping. It is shown that knowledge of the ground-state density is a must to fix the mapping from an excited-state density to an external potential. This is the excited-state counterpart of the Hohenberg–Kohn theorem, where instead of the ground-state density the density of the excited state gives the true many-body wavefunctions of the system. Further, the excited-state Kohn–Sham system is defined by comparing its non-interacting kinetic energy with the true kinetic energy. The theory is demonstrated by studying a large number of atomic systems.

Time-dependent density functional theoretical study of low lying excited states of F2

The utility of time-dependent density functional theory (TDDFT) in predicting excitation energies is tested for the low lying excited states of F 2 , a system that has posed severe challenges to ab initio quantum theory. It is shown that TDDFT using B3LYP functional predicts the excitation energies in good agreement with experiment. In some cases, the agreement is better than that for the post-Hartree-Fock methods like CASSCF and MRCI.

Theoretical study of the size dependence of ionization potential and electron affinity of metallic clusters

Ionization potentials (I) and electron affinities (A) of lithium clusters are studied by treating exchange effects exactly within the exchange‐only density‐functional theory and employing the spherical jellium background model of metallic clusters. In the past, ionization potentials of metallic clusters have been studied by treating the exchange and correlation effects approximately via the local density approximation (LDA). We show that such a calculation leads to ionization potentials which, when extrapolated to large clusters, do not give the correct work function W for the bulk metal as they should. Furthermore, the LDA does not lead to convergent solutions for cluster anions of all sizes. Thus the electron affinities of these clusters cannot be studied within this approximation. On the other hand, by treating exchange effects exactly, solutions for negative ions can also be obtained. We demonstrate that both the ionization potentials and the electron affinities thus obtained extrapolate to the correc...

Calculation of van der Waals coefficients in hydrodynamic approach to time-dependent density functional theory

In this paper we employ hydrodynamic formulation of time-dependent density-functional theory to obtain coefficient C6 of the long-range part of the van der Waals interaction between alkali-metal clusters of large sizes. Such a calculation becomes computationally very demanding in the orbital-based Kohn–Sham formalism, but is quite simple in the hydrodynamic approach. This is because in hydrodynamic formulation, electron density and current density, rather than the orbitals, are employed as basic variables. We show that for intercations between the clusters of same sizes, C6 scales as the sixth power of the cluster radius and approaches the classically predicted value for large size clusters.

Momentum-space properties from coordinate-space electron density

Electron density and electron momentum density, while independently tractable experimentally, bear no direct connection without going through the many-electron wave function. However, invoking a variant of the constrained-search formulation of density-functional theory, we develop a general scheme (valid for arbitrary external potentials) yielding decent momentum-space properties, starting exclusively from the coordinate-space electron density. A numerical illustration of the scheme is provided for the closed-shell atomic systems He, Be, and Ne in their ground state and for 1s(1) 2s(1) singlet electronic excited state for helium by calculating the Compton profiles and the expectation values derived from given coordinate-space electron densities.