The role of the exchange-correlation potential and the exchange-correlation kernel in the calculation of excitation energies from time-dependent density functional theory is studied. Excitation energies of the helium and beryllium atoms are calculated, both from the exact Kohn-Sham ground-state potential, and from two orbital-dependent approximations. These are exact exchange and self-interacti...

We analyze the gauge dependence of the relativistic electron gas correlation energy Ec resulting from the no-pair approximation. In particular, we evaluate the relativistic no-pair Lindhard function as the basic ingredient of the random-phase approximation ~RPA! for Ec . The resulting gauge-dependent no-pair RPA is compared with a gauge-invariant counterpart. The implications for relativistic d...

      In this article, the crystallization of polyethylene is investigated by the modified weighted density approximation. Also, a direct correlation function of polyethylene based on the RISM theory is used. The free energy of a polyethylene is calculated using the density functional theory. The crystallization and also the solid and liquid densities of polyethylene are calculated and compared...

We present the results of calculations on bulk transition metals Rh, Pd, and Pt using the screened hybrid functional YS-PBE0 [F. Tran and P. Blaha, Phys. Rev. B 83, 235118 (2011)]. The results for the equilibrium geometry are compared with those obtained from (semi)local functionals, namely, the local density approximation and the generalized gradient approximation PBE of Perdew et al. [J. P. P...

We discuss a possible form for a theory akin to local density functional theory, but able to produce van der Waals energies in a natural fashion. The usual Local Density Approximation (LDA) for the exchange and correlation energy Exc of an inhomogeneous electronic system can be derived by making a quasilocal approximation for the interacting density-density response function χ(~r, ~r , ω), then...

The reactivity between lithium and the Al13 cluster is studied using the density functional theory and the local density approximation (LDA) for exchange and correlation. The effects caused by the addition of two Li atoms on the structural and electronic properties of the Al cluster are analyzed by calculating equilibrium geometries, binding energies and ionization potentials. The corresponding...

Approximations to the exact density functional for the exchange-correlation energy of a many-electron ground state can be constructed by satisfying constraints that are universal, i.e., valid for all electron densities. Gedanken densities are designed for the purpose of this construction, but need not be realistic. The uniform electron gas is an old gedanken density. Here, we propose a spherica...

We propose approximations which go beyond the local-density approximation for the short-range exchange and correlation density functionals appearing in a multideterminantal extension of the Kohn-Sham scheme. A first approximation consists of defining locally the range of the interaction in the correlation functional. Another approximation, more conventional, is based on a gradient expansion of ...

We construct the complementary short-range correlation relativistic local-density-approximation functional to be used in range-separated density-functional theory based on a Dirac-Coulomb Hamiltonian no-pair approximation. For this, we perform random-phase-approximation calculations of energy homogeneous electron gas with modified electron-electron interaction, study high-density behavior, and ...

Interaction energies for a representative sample of 39 intermolecular complexes are calculated using two computational approaches based on the subsystem formulation of density functional theory introduced by Cortona (Phys. Rev. B 44:8454, 1991), adopted for studies of intermolecular complexes (Wesolowski and Weber in Chem. Phys. Lett. 248:71, 1996). The energy components (exchange-correlation a...