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 removal of trace acetylene from ethylene is performed industrially by palladium hydrogenation catalysts (often modified with silver) that avoid the hydrogenation of ethylene to ethane. In an effort to identify catalysts based on less expensive and more available metals, density functional calculations were performed that identified relations in heats of adsorption of hydrocarbon molecules and fragments on metal surfaces. This analysis not only verified the facility of known catalysts but identified nickel-zinc alloys as alternatives. Experimental studies demonstrated that these alloys dispersed on an oxide support were selective for acetylene hydrogenation at low pressures.

https://science.sciencemag.org/content/sci/320/5881/1320.full.pdf

Identification of non-precious metal alloy catalysts for selective hydrogenation of acetylene

A detailed chemical kinetic mechanism has been developed to describe the oxidation of small hydrocarbon and oxygenated hydrocarbon species. The reactivity of these small fuels and intermediates is of critical importance in understanding and accurately describing the combustion characteristics, such as ignition delay time, flame speed, and emissions of practical fuels. The chosen rate expressions have been assembled through critical evaluation of the literature, with minimum optimization performed. The mechanism has been validated over a wide range of initial conditions and experimental devices, including flow reactor, shock tube, jet-stirred reactor, and flame studies. The current mechanism contains accurate kinetic descriptions for saturated and unsaturated hydrocarbons, namely methane, ethane, ethylene, and acetylene, and oxygenated species; formaldehyde, methanol, acetaldehyde, and ethanol.

A Hierarchical and Comparative Kinetic Modeling Study of C1 − C2 Hydrocarbon and Oxygenated Fuels

https://hal.archives-ouvertes.fr/hal-00848875/document

A comprehensive detailed chemical kinetic reaction mechanism for combustion of n-alkane hydrocarbons from n-octane to n-hexadecane

New experimental profiles of stable species concentrations are reported for formaldehyde oxidation in a variable pressure flow reactor at initial temperatures of 850–950 K and at constant pressures ranging from 1.5 to 6.0 atm. These data, along with other data published in the literature and a previous comprehensive chemical kinetic model for methanol oxidation, are used to hierarchically develop an updated mechanism for CO/H2O/H2/O2, CH2O, and CH3OH oxidation. Important modifications include recent revisions for the hydrogen–oxygen submechanism (Li et al., Int J Chem Kinet 2004, 36, 565), an updated submechanism for methanol reactions, and kinetic and thermochemical parameter modifications based upon recently published information. New rate constant correlations are recommended for CO + OH = CO2 + H (R23) and HCO + M = H + CO + M (R24), motivated by a new identification of the temperatures over which these rate constants most affect laminar flame speed predictions (Zhao et al., Int J Chem Kinet 2005, 37, 282). The new weighted least-squares fit of literature experimental data for (R23) yields k23 = 2.23 × 105T1.89exp(583/T) cm3/mol/s and reflects significantly lower rate constant values at low and intermediate temperatures in comparison to another recently recommended correlation and theoretical predictions. The weighted least-squares fit of literature results for (R24) yields k24 = 4.75 × 1011T0.66exp(−7485/T) cm3/mol/s, which predicts values within uncertainties of both prior and new (Friedrichs et al., Phys Chem Chem Phys 2002, 4, 5778; DeSain et al., Chem Phys Lett 2001, 347, 79) measurements. Use of either of the data correlations reported in Friedrichs et al. (2002) and DeSain et al. (2001) for this reaction significantly degrades laminar flame speed predictions for oxygenated fuels as well as for other hydrocarbons. The present C1/O2 mechanism compares favorably against a wide range of experimental conditions for laminar premixed flame speed, shock tube ignition delay, and flow reactor species time history data at each level of hierarchical development. Very good agreement of the model predictions with all of the experimental measurements is demonstrated. © 2007 Wiley Periodicals, Inc. 39: 109–136, 2007

A comprehensive kinetic mechanism for CO, CH2O, and CH3OH combustion

The time-resolved formation of OH from ethyl + O2 and propyl + O2 reactions has been measured by OH laser-induced fluorescence in pulsed-photolytic Cl-initiated oxidation of ethane and propane between 296 and 700 K. The propane oxidation produces more OH at each temperature than does ethane oxidation. Above 600 K, the peak amplitudes of the OH signals from both reactions increase sharply with increasing temperature. Solutions to the time-dependent master equation for the C2H5 + O2, i-C3H7 + O2, and n-C3H7 + O2 reactions, employing previously published ab initio characterizations of the stationary points of the systems, have been used to produce temperature-dependent parameterizations that predict the rate constants for formation of all of the products (R + O2, RO2, QOOH, OH + aldehydes, OH + O-heterocycles, HO2 + alkene). These parameterizations are utilized in rate equation models to compare to experimental results for HO2 and OH formation in Cl-initiated ethane and propane oxidation. The models accurate...

https://pubs.acs.org/doi/pdf/10.1021/jp040467m

Measurements, theory, and modeling of OH formation in ethyl + O2 and propyl + O2 reactions

The production of HO2 from the reaction of C3H7 and O2 has been investigated as a function of temperature (296−683 K) using laser photolysis/CW infrared frequency-modulation spectroscopy. The HO2 yield is derived by comparison with the Cl2/CH3OH/O2 system and is corrected to account for HO2 signal loss due to competing reactions involving HO2 radical and the adduct C3H7O2. The time behavior of the HO2 signal following propyl radical formation was observed to have two separate components. The first component is a prompt production of HO2, which increases with temperature and is the only HO2 production observed between 296 and 550 K. This prompt yield increases from less than 1% at 296 K to ∼16% at 683 K. At temperatures above 550 K, a second, slower rise in the HO2 signal is also observed. The production of HO2 on a slower time scale is attributable to propylperoxy radical decomposition. The total HO2 yield, including the contribution from the slower rise, increases rapidly with temperature from 5% at 500 ...

Infrared Frequency-Modulation Probing of Product Formation in Alkyl + O2 Reactions: II. The Reaction of C3H7 with O2 between 296 and 683 K

The time-resolved production of HO2 in the Cl-initiated oxidation of iso- and n-butane is measured using continuous-wave (CW) infrared frequency modulation spectroscopy between 298 and 693 K. The yield of HO2 is determined relative to the Cl2/CH3OH/O2 system. As in studies of smaller alkanes, the branching fraction to HO2
+ alkene in butyl + O2 displays a dramatic rise with increasing temperature between about 550 and 700 K (the “transition region”) which is accompanied by a qualitative change in the time behavior of the HO2 production. At low temperatures the HO2 is formed promptly; a second, slower production of HO2 is responsible for the bulk of the increased yield in the transition temperature region. In contrast to reactions of smaller alkyl radicals with O2, the total HO2 yield
in the butyl radical reactions appears to remain significantly below 1 up to 700 K, implying a significant role for OH-producing channels. The slower HO2 production in butane oxidation displays an apparent activation energy similar to that measured for smaller alkyl + O2 reactions, suggesting that the energetics of the HO2 elimination transition state are similar for a broad range of R + O2 systems. A combination of QCISD(T) based characterizations of the propyl and butyl + O2 potential energy surfaces and master equation based characterization of the propyl + O2 kinetics provide the framework for explanation of the experimentally observed HO2 production in Cl-initiated propane and butane oxidation. These calculations suggest that the HO2 elimination channel is similar in all reaction systems, and that hydroperoxyalkyl (QOOH) species produced by internal H-atom
abstraction in RO2 can provide a path to OH formation. However, the QOOH formed by the energetically favorable 1,5 isomerization (ia a six-membered ring transition state) generally experiences significant barriers (relative to the radical + O2 reactants) to the production of an oxetane + OH. In contrast, the barriers to forming OH + an oxirane or an oxolane, ia 1,4 or 1,6 isomerizations, respectively, are generally below reactants.

Infrared frequency-modulation probing of product formation in alkyl + O2 reactions. Part IV. Reactions of propyl and butyl radicals with O2.

The tensile strength, elastic modulus and percent elongation of paraffin wax doped with small concentrations of low density polyethylene (LDPE) where measured. The centrifugal casting process was used to create paraffin wax / LDPE wax hybrid rocket motors. Tensile tests were then performed on samples taken from these test motors. Concentrations from 0 % to 4 % LDPE added to the paraffin wax were tested. The tensile strength, and elastic modulus increased with increasing concentration of LDPE. The results show that paraffin wax motors can be created that have a greater elastic modulus and similar tensile strengths compared to current solid rocket motors based on HTPB rubber motors. However the paraffin wax motors were found to be less elastic than HTPB with a much lower percent elongation. Void formation, tiny bubbles in the paraffin wax created during the casting process, were found to affect the tensile properties measured.

John D. DeSain

Papers

Measurements, theory, and modeling of OH formation in ethyl + O2 and propyl + O2 reactions

Infrared Frequency-Modulation Probing of Product Formation in Alkyl + O2 Reactions: II. The Reaction of C3H7 with O2 between 296 and 683 K

Infrared frequency-modulation probing of product formation in alkyl + O2 reactions. Part IV. Reactions of propyl and butyl radicals with O2.

Tensile Tests of Paraffin Wax for Hybrid Rocket Fuel Grains

High-resolution diode laser absorption spectroscopy of the O-H stretch overtone band (2, 0, 0) ← (0, 0, 0) of the HO2 radical