Debajit Chakraborty

Relationships between the third-order reactivity indicators in chemical density-functional theory

Relationships between third-order reactivity indicators in the closed system [N, v(r)], open system [mu, v(r)], and density [rho(r)] pictures are derived. Our method of derivation unifies and extends known results. Among the relationships is a link between the third-order response of the energy to changes in the density and the quadratic response of the density to changes in external potential. This provides a link between hyperpolarizability and the systems sensitivity to changes in electron density. The dual descriptor is a unifying feature of many of the formulas we derive.

Derivation of Generalized von Weizsäcker Kinetic Energies from Quasiprobability Distribution Functions

The Fisher Information of the electronic distribution functions is closely related to the von Weizsacker kinetic energy functional. We show how generalizations of the Weizsacker kinetic energy density functional can be derived from the canonical momentum-space expression for the kinetic energy and extend this result to higher-order electron distribution functions.

Kinetic Energy Density Functionals from Models for the One-Electron Reduced Density Matrix

Orbital-free kinetic energy functionals can be constructed by writing the one-electron reduced density matrix as an approximate functional of the ground-state electron density. In order to utilize this strategy, one needs to impose appropriate N-representability constraints upon the model 1-electron reduced density matrix. We present several constraints of this sort here, the most powerful of which is based upon the March-Santamaria identity for the local kinetic energy.

Two-point weighted density approximations for the kinetic energy density functional

We construct a model for the one-electron reduced density matrix that is symmetric and which satisfies the diagonal of the idempotency constraint and then use this model to evaluate the kinetic energy. This strategy for designing density functionals directly addresses the N-representability problem for kinetic energy density functionals. Results for atoms and molecules are encouraging, especially considering the simplicity of the model. However, like all of the other kinetic energy functionals in the literature, quantitative accuracy is not achieved.

A Gradient Corrected Two-Point Weighted Density Approximation for Exchange Energies

A successful symmetric, two-point, nonlocal weighted density approximation for the exchange energy of atoms and molecules can be constructed using a power mean with constant power p when symmetrizing the exchange-correlation hole [Phys. Rev. A 85, 042519 (2012)]. In this work, we consider how this parameter depends on the system’s charge. Exchange energies for all ions with charge from \(-1\) to \(+12\) of the first eighteen atoms of the periodic table are computed and optimized. Appropriate gradient corrections to the current model, based on rational functions, are designed based on the optimal p values we observed for the ionic systems. All of the advantageous features (non-locality, uniform electron gas limit and no self-interaction error) of the original model are preserved.