Optimizations of atomic positions belong to the most commonly performed tasks in electronic structure calculations. Many simulations like global minimum searches or characterizations of chemical reactions require performing hundreds or thousands of minimizations or saddle computations. To automatize these tasks, optimization algorithms must not only be efficient but also very reliable. Unfortun...

Judged by whole body dynamics, walking and running in humans clearly differ. When walking, potential and kinetic energy fluctuate out-of-phase and energy is partially recovered in a pendulum-like fashion. In contrast, running involves in-phase fluctuations of the mechanical energy components of the body centre of mass, allowing elastic energy recovery. We show that, when constantly accelerating...

We describe fully quantum, time-independent scattering calculations of the F+H2-->HF+H reaction, concentrating on the HF product rotational distributions in v'=3. The calculations involved two new sets of ab initio potential energy surfaces, based on large basis set, multireference configuration-interaction calculations, which are further scaled to reproduce the experimental exoergicity of the ...

The role of electron-hole pair excitations in the dynamics of N(2) on W(100) and W(110) is evaluated using a theoretical model that accounts for the six-dimensionality of the problem in the whole calculation. The six-dimensional potential energy surface is determined in each case from an extensive grid of energies calculated with density functional theory. Dissipative effects due to electron-ho...

Molecular beam electric deflection measurements have been used to determine electric susceptibilities for small unsolvated alanine-based peptides. The electric susceptibility provides information about the charge distribution within the peptide and can be used to distinguish between zwitterionic and canonical forms. Measured electric susceptibilities for WAn peptides (n = 1-5) are similar to th...

The cyclopropene radical cation (c-C3H₄⁺) is an important but poorly characterized three-membered-ring hydrocarbon. We report on a measurement of the high-resolution photoelectron and photoionization spectra of cyclopropene and several deuterated isotopomers, from which we have determined the rovibrational energy level structure of the X⁺ (2)B2 ground electronic state of c-C3H₄⁺ at low energies...

N-alkoxyheterocycles can act as powerful one-electron acceptors in photochemical electron-transfer reactions. One-electron reduction of these species results in formation of a radical that undergoes N-O bond fragmentation to form an alkoxy radical and a neutral heterocycle. The kinetics of this N-O bond fragmentation reaction have been determined for a series of radicals with varying substituen...

An improved density matrix functional [correction to Buijse and Baerends functional (BBC)] is proposed, in which a hierarchy of physically motivated repulsive corrections is employed to the strongly overbinding functional of Buijse and Baerends (BB). The first correction C1 restores the repulsive exchange-correlation (xc) interaction between electrons in weakly occupied natural orbitals (NOs) a...

To understand the tribological properties of Ne and Kr on Pb(111), the potential energy surfaces for sliding motion of Ne, Kr, and Xe monolayers on the Pb(111) surface are examined through density functional calculations, using either local density or self-consistent nonlocal van der Waals functionals. The calculated adsorption energy for Xe/Pb(111) agrees well with experiment, validating the p...