Inconsistency between molecular structure and energy affecting the dipolar strength between electronic states: a probe into unique inter functional correlations among CAM-B3LYP, LC-\(\omega\)HPBE, \(\omega\)-B97XD functionals

Abstract

Density Functional Theory (DFT) suffers from a strong dichotomy between accuracy and consistency. There exists a paucity of a generic linear route to the systematic improvement of computed results. Benchmark studies are often unidimensional and based on molecular/atomic properties that contour on a single Potential Energy Surface. Thus, the DFT functionals so developed and optimized to similar chemical accuracy lack a universal adherence to the unique density distribution for a fixed nuclear arrangement. We have identified this as a major source of inconsistency within the DFT framework and have explored through the cross-correlations between Structure, Energy, and Dipolar Strength. Since Range Separated Hybrid (RSH) functionals are well-known in literature to produce one of the finest molecular structures in both ground and excited states, in this communication, we have utilized CAM-B3LYP, LC-\(\omega\)HPBE, and \(\omega\)-B97XD to explore the above cross-correlations on well-studied test subjects comprising of Anthracene, Tetracene, Phenanthrene and Pyrene in all possible combination of these functionals. The combined responses from the functionals have revealed that major inconsistency operating between structure and energy dictates the variations in the dipolar strength and that lower RMSD and higher charge reorganization are the keys to higher dipolar strength. While LC-\(\omega\)HPBE stands out, CAM-B3LYP and \(\omega\)B97XD remain comparatively more like each other except in the Adiabatic Energy Difference (AED) trend.

Graphical abstract