Ionisation potential theorem in the presence of the electric field: Assessment of range-separated functional in the reproduction of orbital and excitation energies

Abstract

Recently, the range-separated density functionals have been reported to reproduce gas phase orbital and excitation energies with good accuracy. In this article, we have revisited the ionisation potential theorem in the presence of external electric field. Numerical results on six linear molecules are presented and the performance of the range-separated density functionals in reproducing highest occupied molecular orbital (HOMO) energies, LUMO energies, HOMO-LUMO gaps in the presence of the external electric field is assessed. In addition, valence and Rydberg excitation energies in the presence of the external electric field are presented. It is found that the range-separated density functionals reproduce orbital and excitation energies accurately in the presence of the electric field. Moreover, we have performed fractional occupation calculation using cubic spline equation and tried to explain the performance of the functional.

Understanding Photophysical Properties of Molecules Relevant in Organic Semiconductor Laser Diodes from Electron Localization Function-Tuned and Solvent-Tuned Range-Separated Functionals

“…In the present world, density functional theory (DFT) is considered one of the most extensively used computational tools because of its accuracy and low computational cost. In the sphere of DFT, range-separated (RS) density functionals have attracted the attention of scientists because of their ability to reproduce properties such as charge-transfer excitations, polarizabilities, hyperpolarizabilities, Rydberg excitation, reaction energies, orbital energies, and so forth in which conventional functionals fail. − In addition, tuned RS density functionals are popular because they can reproduce various ground- and excited-state properties with very high accuracy. Nonempirical tuning of RS parameters by the IP tuning scheme is a promising method in the reproduction of various chemical properties in the gas and solvent continuum. − However, in the IP tuning scheme, computations of several self-consistent field (SCF) calculations of neutral and charged species are required, which is computationally expensive.…”

Analytical model for the molecular ionization energy in an external electric field

“…7 In addition, related work adopting quantum chemical calculations mainly discussing the dependence of molecular and cation energies or orbital energies and other molecular properties on the electric field have recently been quite extensive. [8][9][10][11][12][13][14][15] We here suggest a simpler method for calculating the molecular ionization energy in an electric field as compared to the CDFT approach that results in analytical function dependent on the electric field and on molecular properties calculated without an electric field. It is expected that the model can be used directly in coarse-grained methods for electronic processes where the molecular ionization energy is needed.…”

Analytical Model for the Molecular Ionization Energy in an External Electric Field

“…A theoretically more elaborate model for one- and two-electron systems has previously been presented . In addition, related works adopting quantum chemical calculations mainly discussing the dependence of molecular and cation energies or orbital energies and other molecular properties on the electric field have recently been quite extensive. − …”