P. Sule | Searcharxiv

arXiv1999

Perturbation Theory on Top of Optimized Effective Potential Method

We present a perturbative approach within the scope of Kohn-Sham density functional theory (DFT). The method is based on the exact exchange-only optimized effective potential method, and correlation is included via perturbation expansion using Rayleigh-Schrodinger (RS) perturbation theory (PT). The correlation potential is constructed from Moller-Plesset formulation of RS calculations. This naturally leads to a new iterative scheme when finite order perturbation theory is employed. The new iterative procedure can be taken as a self-consistent parameter-free DFT PT, and, as such, provides correlation energy which is explicitly functional of the self-consistent orbitals, eigenvalues and also of the exchange-correlation potential.

physics.chem-ph↗

arXiv1999

Optimized Effective Potential Method for Polymers

The optimized effective potential (OEP) method allows for calculation of the local, effective single particle potential of density functional theory for explicitly orbital-dependent approximations to the exchange-correlation energy functional. In the present work the OEP method is used together with the approximation due to Krieger, Li and Iafrate (KLI). We present the first application of this method to polymers. KLI calculations have been performed for the insulating polyethylene and the results have been compared to those from other orbital-dependent potentials. Various properties of the band structure are also calculated. The single-particle band gap strongly depends on the basis set with larger basis sets yielding narrow gaps. For the highest occupied orbital energy the difference is more pronounced. In order to get the right band gap in OEP the exchange contribution to the derivative discontinuity is calculated and added to the Kohn-Sham gap.

cond-mat.mtrl-sci↗