title: 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.
authors.affiliation: Department of Chemistry, Dibrugarh University, Dibrugarh, Assam 786004, India.
authors.forename: Manash Protim
authors.initials: MP
authors.lastname: Borpuzari
authors.affiliation: Department of Chemistry, Dibrugarh University, Dibrugarh, Assam 786004, India.
authors.forename: Abhijit
authors.initials: A
authors.lastname: Boruah
authors.affiliation: Department of Chemistry, Dibrugarh University, Dibrugarh, Assam 786004, India.
authors.forename: Rahul
authors.initials: R
authors.lastname: Kar