Dataset of noncovalent intermolecular interaction energy curves for 24 small high-spin open-shell dimers.

We introduce a dataset of 24 interaction energy curves of open-shell noncovalent dimers, referred to as the O24 × 5 dataset. The dataset consists of high-spin dimers up to 11 atoms selected to assure diversity with respect to interaction types: dispersion, electrostatics, and induction. The benchmark interaction energies are obtained at the restricted open-shell CCSD(T) level of theory with complete basis set extrapolation (from aug-cc-pVQZ to aug-cc-pV5Z).

The nature of three-body interactions in DFT: Exchange and polarization effects.

We propose a physically motivated decomposition of density functional theory (DFT) 3-body nonadditive interaction energies into the exchange and density-deformation (polarization) components. The exchange component represents the effect of the Pauli exclusion in the wave function of the trimer and is found to be challenging for density functional approximations (DFAs). The remaining density-deformation nonadditivity is less dependent upon the DFAs.

Tuned range-separated hybrid functionals in the symmetry-adapted perturbation theory.

The aim of this study is to present a performance test of optimally tuned long-range corrected (LRC) functionals applied to the symmetry-adapted perturbation theory (SAPT). In the present variant, the second-order energy components are evaluated at the coupled level of theory. We demonstrate that the generalized Kohn-Sham (GKS) description of monomers with optimally tuned LRC functionals may be essential for the quality of SAPT interaction energy components.

Density-dependent onset of the long-range exchange: a key to donor-acceptor properties.

Quantum mechanical methods based on the density functional theory (DFT) offer a realistic possibility of first-principles design of organic donor-acceptor systems and engineered band gap materials. This promise is contingent upon the ability of DFT to predict one-particle states accurately. Unfortunately, approximate functionals fail to align the orbital energies with ionization potentials.

A first-principles-based correlation functional for harmonious connection of short-range correlation and long-range dispersion.

We present a physically motivated correlation functional belonging to the meta-generalized gradient approximation (meta-GGA) rung, which can be supplemented with long-range dispersion corrections without introducing double-counting of correlation contributions. The functional is derived by the method of constraint satisfaction, starting from an analytical expression for a real-space spin-resolved correlation hole. The model contains a position-dependent function that controls the range of the interelectronic correlations described by the semilocal functional.

Dispersion-free component of non-covalent interaction via mutual polarization of fragment densities.

Comprehensive tests within a diverse set of noncovalently bonded systems are carried out to assess the performance of the recently-developed dispersion-free approach in the framework of density functional theory [Ł. Rajchel, P. Żuchowski, M.

A density functional theory approach to noncovalent interactions via interacting monomer densities.

A recently proposed "DFT + dispersion" treatment (Rajchel et al., Phys. Rev.

Density functional theory approach to noncovalent interactions via monomer polarization and Pauli blockade.

We propose a "DFT+dispersion" treatment which avoids double counting of dispersion terms by deriving the dispersion-free density functional theory (DFT) interaction energy and combining it with DFT-based dispersion. The formalism involves self-consistent polarization of DFT monomers restrained by the exclusion principle via the Pauli-blockade technique. Any exchange-correlation potential can be used within monomers, but only the exchange operates between them.

Nonadditive interactions in ns2 and spin-polarized ns metal atom trimers.

The origins of nonadditivity in the following groups of metal trimers are examined: alkali earth metals of the IIA group (Be, Mg, and Ca), Zn as a transition metal analog of this group, spin-polarized alkali metals from IA group (Li, Na, K), and the spin-polarized Cu as its transition metal analog. The nonadditive interactions in these trimers are analyzed using the following hierarchy of approximations: the Heitler-London, self-consistent field (SCF), and correlated levels of theory. The exchange nonadditivity, which is included at the Heitler-London level, constitutes a bulk of nonadditive interactions in these systems in their equilibrium structures.

Interactions of transition metal atoms in high-spin states: Cr2, Sc-Cr, and Sc-Kr.

The high-spin van der Waals states are examined for the following dimers: Cr(2) ((13)Sigma(g)(+)), Sc-Cr ((8)Sigma(+), (8)Pi, (8)Delta), and Sc-Kr ((2)Sigma(+), (2)Pi, (2)Delta). These three systems offer a wide range of van der Waals interactions: anomalously strong, intermediate, and typically weak. The single-reference [coupled cluster with single, double, and noniterative triple excitations, RCCSD(T)] method is used in the calculations for all three systems.

Interactions in open-shell clusters: ab initio study of pre-reactive complex O(3P) + HCl.

Van der Waals interactions between the ground-state triplet O(3P) atom and the closed-shell HCl molecule are investigated in the pre-reactive region. Three adiabatic (two of A'' symmetry and one of A' symmetry) and four non-relativistic diabatic potential energy surfaces are obtained by combining a restricted open-shell coupled cluster approach with the multireference configuration interaction method. The lower A'' adiabatic potential surface has a single minimum (D(e) = 589 cm(-1)) for a linear O.