We present the theoretical and technical foundations of the Amsterdam Density Functional (ADF) program with a survey of the characteristics of the code (numerical integration, density fitting for the Coulomb potential, and STO basis functions). Recent developments enhance the efficiency of ADF (e.g., parallelization, near order-N scaling, QM/MM) and its functionality (e.g., NMR chemical shifts, COSMO solvent effects, ZORA relativistic method, excitation energies, frequency-dependent (hyper)polarizabilities, atomic VDD charges). In the Applications section we discuss the physical model of the electronic structure and the chemical bond, i.e., the Kohn–Sham molecular orbital (MO) theory, and illustrate the power of the Kohn–Sham MO model in conjunction with the ADF-typical fragment approach to quantitatively understand and predict chemical phenomena. We review the “Activation-strain TS interaction” (ATS) model of chemical reactivity as a conceptual framework for understanding how activation barriers of various types of (competing) reaction mechanisms arise and how they may be controlled, for example, in organic chemistry or homogeneous catalysis. Finally, we include a brief discussion of exemplary applications in the field of biochemistry (structure and bonding of DNA) and of time-dependent density functional theory (TDDFT) to indicate how this development further reinforces the ADF tools for the analysis of chemical phenomena. © 2001 John Wiley & Sons, Inc. J Comput Chem 22: 931–967, 2001

Chemistry with ADF

The Gaussian‐2 theoretical procedure (G2 theory), based on a b i n i t i o molecular orbital theory, for calculation of molecular energies (atomization energies, ionization potentials,electron affinities, and proton affinities) of compounds containing first‐ (Li–F) and second‐row atoms (Na–Cl) is presented. This new theoretical procedure adds three features to G1 theory [J. Chem. Phys. 9 0, 5622 (1989)] including a correction for nonadditivity of diffuse‐s p and 2d f basis set extensions, a basis set extension containing a third d function on nonhydrogen and a second p function on hydrogen atoms, and a modification of the higher level correction. G2 theory is a significant improvement over G1 theory because it eliminates a number of deficiencies present in G1 theory. Of particular importance is the improvement in atomization energies of ionic molecules such as LiF and hydrides such as C2H6, NH3, N2H4, H2O2, and CH3SH. The average absolute deviation from experiment of atomization energies of 39 first‐row compounds is reduced from 1.42 to 0.92 kcal/mol. In addition, G2 theory gives improved performance for hypervalent species and electron affinities of second‐row species (the average deviation from experiment of electron affinities of second‐row species is reduced from 1.94 to 1.08 kcal/mol). Finally, G2 atomization energies for another 43 molecules, not previously studied with G1 theory, many of which have uncertain experimental data, are presented and differences with experiment are assessed.

Gaussian-2 theory for molecular energies of first- and second-row compounds

In this Account we have compiled a list of reliable bond energies that are based on a set of critically evaluated experiments. A brief description of the three most important experimental techniques for measuring bond energies is provided. We demonstrate how these experimental data can be applied to yield the heats of formation of organic radicals and the bond enthalpies of more than 100 representative organic molecules.

Bond Dissociation Energies of Organic Molecules

Bond dissociation energies of organic molecules

I. Introduction and Scope 231A. Definitions of Atomic Electron Affinities 233B. Definitions of Molecular Electron Affinities 233II. Experimental Photoelectron Electron Affinities 235A. Historical Background 235B. The Photoeffect 236C. Experimental Methods 237D. Time-of-Flight Negative Ion PhotoelectronSpectroscopy239E. Some Thermochemical Uses of ElectronAffinities241F. Layout of Table 10: ExperimentalPhotoelectron Electron Affinities242III. Theoretical Determination of Electron Affinities 242A. Historical Background 2421. Theoretical Predictions of Atomic ElectronAffinities2422. Theoretical Predictions of MolecularElectron Affinities243B. Present Status of Theoretical Electron AffinityPredictions243C. Basis Sets and Theoretical Electron Affinities 244D. Density Functional Theory (DFT) andElectron Affinities245E. Layout of Tables 8 and 9: Theoretical DFTElectron Affinities247F. Details of Density Functional MethodsEmployed in Tables 8 and 9247IV. Discussion and Observations 248A. Statistical Analysis of DFT Results ThroughComparisons to Experiment and OtherTheoretical Methods248B. Theoretical EAs for Species with UnknownExperimental EAs251C. On the Applicability of DFT to Anions and theFuture of DFT EA Predictions251D. Specific Theoretical Successes 251E. Interesting Problems 2521. C

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Atomic and molecular electron affinities: photoelectron experiments and theoretical computations.

: The reactions of trimethyl phosphite were investigated with a series of nucleophiles. Products, branching ratios, and reaction rate constants are reported. Reactions generally proceed through an ion-dipole complex (Z-. (CH3O) 3P), to a phosphoranide anion intermediate, (CH3O)3PZ-), to displacement of methoxide to form a new ion-dipole complex (CH3O-(CH3O)2PZ). If an additional acidic hydrogen is available on the nucleophile, the major products result from proton abstraction by methoxide: (CH3O-.(CH30)2PYH) yield (CH30)2PY-+CH3OH. While the displacement of methoxide from phosphorus is sufficiently endothermic, a competing attack at carbon by the original nucleophile occurs: (HY-.(CH3O)3P) yields CH3YH+ (CH3O)2Po-. Nucleophiles without an additional acidic hydrogen react similarly, but the final reaction products result from 1) SN2 reaction of methoxide, 2) SN2 reaction of the original nucleophile, and 3) stabilization of the phosphoranide intermediate, and 4) expulsion of methoxide from the ion- dipole complex. Reaction mechanisms are discussed in terms of the nature of the nucleophiles, the observed products, and the thermodynamics of the displacement reaction. Originator-supplied keywords include: Flowing afterglow; Trimethyl phosphite; Reaction mechanisms; Phosphorous; and Nucleophilic displacement.

Gas-phase chemistry of trimethyl phosphite

Siloxide ions undergo O/S exchange reactions with suitable sulfur-containing neutrals, e.g. H3SiO-+CS2 → H3SiS-+COS. Silamide ions similarly undergo NR/O and NR/S exchange reactions together with nucleophilic displacement reactions, e.g. Me3SiNMe + CO2 → Me3SiO-+MeNCO →No simple correlation between rate and mechanism is observed for all the studied reactions.

Charles H. DePuy

Papers

Gas-phase chemistry of trimethyl phosphite

Gas Phase Ion Chemistry of Siloxide and Silamide Ions by Using the Flowing Afterglow. Unusual Rearrangements Involving SiO and SiS Bond Formation.