Application of the subspace density functional theory to the excitation energies of molecules

Abstract

The performance of the subspace density functional theory in its local density approximation is investigated by applications to the excitation energies of small molecules. The different schemes, concerning the choice of finite basis sets, for treating in a balanced way the ground and excited state calculations, are discussed. Unlike the conventional atom centred basis sets, we used off centred basis sets whose parameters were determined by invoking the minimum principle for the subspace energy. For the molecules under consideration (H2, HeH and LiH) such basis sets consisting only of s-type Gaussians, optimized for each subspace energy, were found to provide a reasonable agreement of the excitation energies computed with those obtained by the configuration interaction methods with extended basis sets.

Calculation of electronic excited states of molecules using the Helmholtz free-energy minimum principle

“…Since the trace is invariant under rotation of the basis vectors and depends only on the m-dimensional space, Theophilou named the approach based on his theorem the subspace method, i.e., the subspace Hartree-Fock [4] as well as the subspace DFT [1,5,6]. The GOK variational principle with the flexibility of different weights (for nondegenerate states) affords not only the energies of the first m states, but also of the wave functions themselves.…”

DFT with effective potential expressed as a mapping of the external potential: Applications to closed‐shell molecules

“…, which is high relative to standard DFT, implemented within the local density approximation [37]. Note that these results do not have yet any correlation energy correction.…”

“…One also expects increased accuracy for large molecules relative to the commonly used method of atom-centered Gaussians. Such basis sets were found to provide a balanced description for an ensemble of states within the subspace density functional theory [37].…”

A road to a multiconfigurational ensemble density functional theory without ghost interactions

“…[15,16] This new theory in principle capable of describing double excitations and potential energy surfaces became on object of extensive theoretical research [17][18][19][20][21] and a few numerical implementations. [21][22][23][24] Due to the lack of good approximation of the ensemble exchange-correlation functionals and the difficulties associated with imposing the orthogonality condition on the wavefunctions those realizations have been so far rather scarce and only moderately successful, apart from the pragmatic approach of Filatov and coworkers. [25,26] In our previous work [27] we proposed two methods of calculation, based on the EVP.…”