A remarkably simple dispersion damping scheme and the DH24 double hybrid density functional.

In recent papers, Becke et al. [J. Chem.

Doubling down on density-functional theory.

In a recent paper, Becke et al. [J. Chem.

A double-hybrid density functional based on good local physics with outstanding performance on the GMTKN55 database.

In two recent papers [A. D. Becke, J.

Density-functional theory vs density-functional fits: The best of both.

In a recent paper [A. D. Becke, J.

Density-functional theory vs density-functional fits.

Kohn-Sham density-functional theory (DFT), the predominant framework for electronic structure computations in chemistry today, has undergone considerable evolution in the past few decades. The earliest DFT approximations were based on uniform electron gas models completely free of empirical parameters. Tremendous improvements were made by incorporating density gradients and a small number of parameters, typically one or two, obtained from fits to atomic data.

Computational modeling of piezochromism in molecular crystals.

Piezochromic materials, whose luminescence responds to external pressure, have recently garnered much experimental attention. Computational modeling of piezochromism is of high theoretical interest, yet currently lacking. Herein, we present a computational effort to predict the piezochromism for a selection of molecular crystals.

Quantum Chemical Methods for Modeling Covalent Modification of Biological Thiols.

Targeted covalent inhibitor drugs require computational methods that go beyond simple molecular-mechanical force fields in order to model the chemical reactions that occur when they bind to their targets. Here, several semiempirical and density-functional theory (DFT) methods are assessed for their ability to describe the potential energy surface and reaction energies of the covalent modification of a thiol by an electrophile. Functionals such as PBE and B3LYP fail to predict a stable enolate intermediate.

Dependence of the virial exciton model on basis set and exact-exchange fraction.

The exchange-only (uncorrelated) singlet-triplet energy difference in one-electron excited configurations is 2K, where K is the Coulomb self-energy of the product of the transition orbitals. A nonempirical, virial-theorem argument was presented by Becke [J. Chem.

Communication: Becke's virial exciton model gives accurate charge-transfer excitation energies.

First singlet (S) excitations are of primary importance in the photoluminescence spectra of organic chromophores. However, due to the multi-determinantal nature of the singlet excited states, standard Kohn-Sham density-functional theory (DFT) is not applicable. While linear-response time-dependent DFT is the method of choice for the computation of excitation energies, it fails severely for excitations with charge-transfer character.

Density-functional description of alkalides: introducing the alkalide state.

Alkalides are crystalline salts in which the anion is a negatively charged alkali metal. A systematic investigation of the electronic structure of thirteen alkalides, with known crystal structures, is conducted using density-functional theory. For each alkalide, a high-lying valence state is identified that is localised on the alkali anions and is consistent with the low band gap and strong reducing power characteristic of these materials.

Pervasive Delocalisation Error Causes Spurious Proton Transfer in Organic Acid-Base Co-Crystals.

Dispersion-corrected density-functional theory (DFT-D) methods have become the workhorse of many computational protocols for molecular crystal structure prediction due to their efficiency and convenience. However, certain limitations of DFT, such as delocalisation error, are often overlooked or are too expensive to remedy in solid-state applications. This error can lead to artificial stabilisation of charge transfer and, in this work, it is found to affect the correct identification of the protonation site in multicomponent acid-base crystals.

Communication: Optical gap in polyacetylene from a simple quantum chemistry exciton model.

A recent virial-theorem-based model of the singlet-triplet splitting in singly excited configurations [A. D. Becke, J.

Communication: Correct charge transfer in CT complexes from the Becke'05 density functional.

It has been known for over twenty years that density functionals of the generalized-gradient approximation (GGA) type and exact-exchange-GGA hybrids with low exact-exchange mixing fraction yield enormous errors in the properties of charge-transfer (CT) complexes. Manifestations of this error have also plagued computations of CT excitation energies. GGAs transfer far too much charge in CT complexes.

Singlet-triplet splittings from the virial theorem and single-particle excitation energies.

The zeroth-order (uncorrelated) singlet-triplet energy difference in single-particle excited configurations is 2K, where K is the Coulomb self-energy of the product of the transition orbitals. Here we present a non-empirical, virial-theorem argument that the correlated singlet-triplet energy difference should be half of this, namely, K. This incredibly simple result gives vertical HOMO-LUMO excitation energies in small-molecule benchmarks as good as the popular TD-B3LYP time-dependent approach to excited states.

Interrogating the Becke'05 density functional for non-locality information.

In two papers, Becke [J. Chem. Phys.

Communication: DFT treatment of strong correlation in 3d transition-metal diatomics.

Bonds between, and to, transition-metal atoms often involve strong electron correlation which cannot be handled by conventional density-functional-theory approximations. The recent "B13" functional of Becke [J. Chem.

Vertical excitation energies from the adiabatic connection.

Vertical single-particle excitations from closed-shell ground states are complicated by the fact that the singlet open-shell states are, even in the first approximation, two-determinantal. Thus two-electron integrals come into play and standard time-independent DFT (density-functional theory) does not apply. In this work, we use the "adiabatic connection" to analyse the role of the two-electron integrals, obtaining a time-independent DFT approach to excitation-energy calculations that is new and simple.

Perspective: Fifty years of density-functional theory in chemical physics.

Since its formal inception in 1964-1965, Kohn-Sham density-functional theory (KS-DFT) has become the most popular electronic structure method in computational physics and chemistry. Its popularity stems from its beautifully simple conceptual framework and computational elegance. The rise of KS-DFT in chemical physics began in earnest in the mid 1980s, when crucial developments in its exchange-correlation term gave the theory predictive power competitive with well-developed wave-function methods.

Communication: Two-determinant mixing with a strong-correlation density functional.

In recent papers [A. D. Becke, J.

Communication: Calibration of a strong-correlation density functional on transition-metal atoms.

In recent work [A. D. Becke, J.

Density functionals for static, dynamical, and strong correlation.

In this work, our exact-exchange-based static + dynamical correlation density functional [A. D. Becke, J.

Assessment of the PW86+PBE+XDM density functional on van der Waals complexes at non-equilibrium geometries.

The deficiency of conventional density-functional theory (DFT) in properly describing van der Waals (vdW) (especially dispersion-bound) complexes has been extensively addressed in the past decade. There are now several new methods published in the literature that are capable of accurately capturing weak dispersion interactions in complexes at equilibrium geometries. However, the performance of these new methods at non-equilibrium geometries remains to be assessed.

Atomic volumes and polarizabilities in density-functional theory.

Becke and Johnson introduced an ad hoc definition of atomic volume [J. Chem. Phys.

A density-functional approximation for relativistic kinetic energy.

A density-functional approximation for the relativistic kinetic energy of a many-electron system is introduced, depending on the total particle density and the (nonrelativistic) kinetic energy density. The resulting scalar variational orbital equation is similar to Schrodinger's nonrelativistic equation, but includes relativistic mass-velocity effects to all orders in p. We test the theory by computing relativistic orbitals in the uranium atom and comparing their energies and mean radii with Dirac and zeroth-order regular approximation results.

Oscillations in meta-generalized-gradient approximation potential energy surfaces for dispersion-bound complexes.

Meta-generalized-gradient approximations (meta-GGAs) in density-functional theory are exchange-correlation functionals whose integrands depend on local density, density gradient, and also the kinetic-energy density. It has been pointed out by Johnson et al. [Chem.