# Density functional electric response properties of molecules in Cartesian grid

## TL;DR

This paper presents a Cartesian grid-based DFT approach to calculate electric response properties of diatomic molecules, demonstrating accuracy and convergence comparable to traditional atom-centered methods.

## Contribution

It develops and validates a Cartesian grid implementation for DFT electric response calculations, including grid convergence analysis and application to molecules at various geometries.

## Key findings

- Excellent agreement with atom-centered-grid results
- Accurate response properties for HCl, HBr, HI
- Reliable results for molecules far from equilibrium

## Abstract

Within the finite-field Kohn-Sham framework, static electric response properties of diatomic molecules are presented. The electronic energy, dipole moment ({\boldmath$\mu$}), static dipole polarizability ({\boldmath$\alpha$}) and first-hyperpolarizability ({\boldmath$\beta$}) are calculated through a pseudopotential-DFT implementation in Cartesian coordinate grid, developed in our laboratory earlier. We engage the Labello-Ferreira-Kurtz (LFK) basis set; while four local and non-local exchange-correlation (LDA, BLYP, PBE and LBVWN) functionals have been adopted. A detailed analysis of \emph{grid convergence} and its impact on obtained results, is presented. In each case the \emph{electric field optimization} was carefully monitored through a recently prescribed technique. For all three molecules (HCl, HBr, HI) considered, the agreement of all these quantities with widely successful and popular atom-centered-grid procedure, is excellent. To assess the efficacy and feasibility, companion calculations are performed for these on a representative molecule (HCl) at distorted geometries, far from equilibrium. Wherever possible, relevant comparison is made with available \emph{all-electron} data and experimental results. This demonstrates that Cartesian grid provides accurate, reliable results for such properties of many-electron systems within pseudopotential representation.