"Chemists familiar with conventional quantum mechanics will applaud and benefit greatly from this particularly instructive, thorough and clearly written exposition of density functional theory: its basis, concepts, terms, implementation, and performance in diverse applications. Users of DFT for structure, energy, and molecular property computations, as well as reaction mechanism studies, are guided to the optimum choices of the most effective methods. Well done!" Paul von RaguE Schleyer "A conspicuous hole in the computational chemist's library is nicely filled by this book, which provides a wide-ranging and pragmatic view of the subject.[...It] should justifiably become the favorite text on the subject for practioneers who aim to use DFT to solve chemical problems." J. F. Stanton, J. Am. Chem. Soc. "The authors' aim is to guide the chemist through basic theoretical and related technical aspects of DFT at an easy-to-understand theoretical level. They succeed admirably." P. C. H. Mitchell, Appl. Organomet. Chem. "The authors have done an excellent service to the chemical community. [...] A Chemist's Guide to Density Functional Theory is exactly what the title suggests. It should be an invaluable source of insight and knowledge for many chemists using DFT approaches to solve chemical problems." M. Kaupp, Angew. Chem.

A Chemist's Guide to Density Functional Theory

A scheme that reduces the calculations of ground-state properties of systems of interacting particles exactly to the solution of single-particle Hartree-type equations has obvious advantages. It is not surprising, then, that the density functional formalism, which provides a way of doing this, has received much attention in the past two decades. The quality of the energy surfaces calculated using a simple local-density approximation for exchange and correlation exceeds by far the original expectations. In this work, the authors survey the formalism and some of its applications (in particular to atoms and small molecules) and discuss the reasons for the successes and failures of the local-density approximation and some of its modifications.

The density functional formalism, its applications and prospects

The halogen bond occurs when there is evidence of a net attractive interaction between an electrophilic region associated with a halogen atom in a molecular entity and a nucleophilic region in another, or the same, molecular entity. In this fairly extensive review, after a brief history of the interaction, we will provide the reader with a snapshot of where the research on the halogen bond is now, and, perhaps, where it is going. The specific advantages brought up by a design based on the use of the halogen bond will be demonstrated in quite different fields spanning from material sciences to biomolecular recognition and drug design.

The Halogen Bond

The detection methods and generation mechanisms of the intrinsic reactive oxygen species (ROS), i.e., superoxide anion radical (•O2–), hydrogen peroxide (H2O2), singlet oxygen (1O2), and hydroxyl radical (•OH) in photocatalysis, were surveyed comprehensively. Consequently, the major photocatalyst used in heterogeneous photocatalytic systems was found to be TiO2. However, besides TiO2 some representative photocatalysts were also involved in the discussion. Among the various issues we focused on the detection methods and generation reactions of ROS in the aqueous suspensions of photocatalysts. On the careful account of the experimental results presented so far, we proposed the following apprehension: adsorbed •OH could be regarded as trapped holes, which are involved in a rapid adsorption–desorption equilibrium at the TiO2–solution interface. Because the equilibrium shifts to the adsorption side, trapped holes must be actually the dominant oxidation species whereas •OH in solution would exert the reactivity...

Generation and Detection of Reactive Oxygen Species in Photocatalysis

: The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Ab initio calculation of vibrational absorption and circular dichroism spectra using density functional force fields

Iodine vapor was suspended in Ar, Kr, Xe and N2 matrices at 16K using several dilutions (Ar/I2=400/1, 1000/1, 2500/1) and the Raman spectra were studied using krypton and argon plasma exciting lines. Two progressions were observed in the Ar/I2=400 samples: a weak one beginning at 212±1 cm−1, which has the gas-phase I2 spacing, and extending out to 11ν using 5145 A excitation, and a very strong series beginning at 180 ± 1 cm−1 and extending out to 11ν with vibrational intervals near solid I2 values. The two progressions exhibited comparable intensities in the Ar/I2=1000 experiment. In the Ar/I2=2500 experiments, the gas-phase-like series was intense and the 180 cm−1 interval spectrum was absent. The very strong I2 fundamental and regular overtone progressions increased in length and in intensity as the exciting wavelength decreased 6471 to 5145 A, reaching the absorption band maximum, and then decreased in length and intensity using 4880 and 4579 A excitation. These observations are characteristic of resonance Raman spectra.

Matrix Raman spectra of the molecular halogens: Resonance Raman spectra of isolated and aggregated I2

Reactions of laser-ablated Ga atoms and normal hydrogen during co-deposition at 3.5 K give GaH as the major product and GaH2, GaH3, GaH2-, GaH4-, and Ga2H2 as minor products. Identifications are based on infrared spectra, isotopic substitution (D2, H2 + D2 mixtures, HD), comparisons to earlier work, and frequencies calculated by density functional theory. Mercury arc radiation destroyed the GaH2- and GaH4- anions, decreased GaH and increased GaH3, destroyed Ga2H2, and produced new bands due to Ga2H4, two Ga2H5 radical isomers, and Ga2H6. ArF laser irradiation at 193 nm was particularly effective in converting GaH to GaH3 and to Ga2H6. The GaH4- anion absorptions in solid hydrogen are compatible with solid NaGaH4 bands:  Near-ultraviolet excitation of GaD2- with D2 present increases GaD4- absorptions. Warming these samples to remove the H2 matrix replaced sharp gallium hydride molecular absorptions with broad 1800−2000, 1300−1700, and 600−700 cm-1 bands due to higher oligomers containing terminal and bridg...

Infrared Spectra of Gallium Hydrides in Solid Hydrogen: GaH1,2,3, Ga2H2,4,6, and the GaH2,4- Anions

FTIR spectra of Ar/CO/HF mixtures rapidly frozen at 12 and 5 K contained a weak new absorption at 3907 cm/sup -1/ in addition to the strong OC--HF complex band at 3789 cm/sup -1/. The DF counterpart absorbance at 2866 cm/sup -1/ was a larger fraction of the absorbance for OC--DF at 2781 cm/sup -1/. The former new bands were generally favored by slower spray-on rates and were destroyed on annealing that increased the latter bands. These weaker new bands are assigned to the reverse complexes CO--HF and CO--DF that calculations predict to be less stable than the carbon-bonded structures observed in the gas phase and in larger yield in matrices. An analogous situation was found for Ar/HCN/HF mixtures which revealed both HF--HCN and HCN--HF. Apparently matrix formation relaxes these molecules fast enough to trap the less stable complex structures that are not observed in supersonic nozzle expansion experiments.

Matrix trapping of two structural arrangements of weak complexes

Infrared Spectra of the Reaction Products of Laser-Ablated Titanium Atoms and Oxides with Carbon Monoxide in Solid Argon

The argon matrix Raman spectra of oxygen difluoride and oxygen‐18 difluoride at 16°K have been observed; frequencies within one wavenumber of analogous infrared studies were measured. Laser photo‐detachment of fluorine atoms has provided significant yields of the OF and 18OF free radicals; the Raman observations confirm the earlier infrared work. Temperature cycling operations and depolarization ratio measurements provide aid in identifying new chemical species and making vibrational assignments.

Lester Andrews

Papers

Matrix Raman spectra of the molecular halogens: Resonance Raman spectra of isolated and aggregated I2

Infrared Spectra of Gallium Hydrides in Solid Hydrogen: GaH1,2,3, Ga2H2,4,6, and the GaH2,4- Anions

Matrix trapping of two structural arrangements of weak complexes

Infrared Spectra of the Reaction Products of Laser-Ablated Titanium Atoms and Oxides with Carbon Monoxide in Solid Argon

Argon Matrix Raman Spectra of Oxygen Difluoride and the Oxygen Fluoride Free Radical