"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

Raman spectra of samples of sodium and potassium atoms codeposited at 16°K with oxygen molecules at high dilution in argon showed strong bands at 1094 and 1108 cm−1, respectively, which are assigned to the superoxide fundamentals in the Na+O2− and K+O2− molecules. These features were split into triplets using 16O2, 16O18O, 18O2 samples, which indicates isosceles triangular structures; absence of M+–O2− interionic modes confirms the ionic model for the alkali superoxide molecules. Infrared bands at 1079 and 1097–1104 cm−1 in Na and K atom −O2 reactions, respectively, are assigned to the dimeric species (M+O2−)2. The symmetric metal‐oxygen mode for O2KO2 was observed in the Raman at 305 cm−1, inferring more covalent character in the metal oxygen bonding in this species than in the alkali superoxides.

Raman Spectra of the Products of Na and K Atom Argon Matrix Reactions with O2 Molecules

Laser-ablated Ni atoms and electrons react with CO in excess argon during condensation to form the Ni(CO)1-4 complexes and Ni(CO)1-3- anions. Matrix infrared spectra of the neutral complexes with 12C16O, 13C16O, and 12C18O substitution are in agreement with earlier reports with thermal Ni atoms. In addition, new absorptions at 1847.0, 1801.7, and 1858.8 cm-1 exhibit isotopic spectra in excellent agreement with DFT calculations for the Ni(CO)1-3- anions. An experiment doped with the CCl4 electron-trapping molecule gave the same Ni(CO)1-4 spectrum without the corresponding anions, which strongly supports this identification of the molecular anions.

Matrix Infrared Spectra and Density Functional Calculations of Ni(CO)x-, x = 1−3

Sulfur vapor was seeded into a microwave-powered argon discharge and condensed at 12 K. Infrared spectra revealed sharp strong bands at 680.0, 676.2, 661.6, and 642.4 cm{sup {minus}1}, which were also observed by thermal dissociation of S{sub 8} flowing in a quartz tube heated to 400-900{degree}C. Increasing the sulfur concentration in the discharge favored the latter two relative to the former two absorptions. Enriched {sup 34}S samples gave isotopic shifts for pure sulfur fundamentals and isotopic multiplets that identify these species. Sample annealing produced a strong S{sub 2} chemiluminescence and a sharp new 674.5-cm{sup {minus}1} band. This feature revealed a sharp 1/2/1/1/2/1 sextet with 50/50 {sup 32}S/{sup 34}S, which confirms the observation of C{sub 2v} thiozone; similar multiplets were found for the 680.0- and 676.2-cm{sup {minus}1} bands. Calculations from four pairs of symmetrical isotopic v{sub 3} values gave 116 {plus minus} 2{degree} for the valence angle.

Infrared spectra and structures of isotopically enriched sulfur (S3 and S4) in solid argon

Gold is noble, but excited gold is reactive. Reactions of laser-ablated copper, silver, and gold with H(2) in excess argon, neon, and pure hydrogen during condensation at 3.5 K give the MH molecules and the (H(2))MH complexes as major products and the MH(2)(-) and AuH(4)(-) anions as minor products. These new molecular anions are identified from matrix infrared spectra with isotopic substitution (HD, D(2), and H(2) + D(2)) and comparison to frequencies calculated by density functional theory. The stable linear MH(2)(-) anions are unique in that their corresponding neutral MH(2) molecules are higher in energy than M + H(2) and thus unstable to M + H(2) decomposition. Infrared spectra are observed for the bending modes of AuH(2), AuHD, and AuD(2) in solid H(2), HD, and D(2), respectively. The observation of square-planar AuH(4)(-) attests the stability of the higher Au(III) oxidation state for gold. The synthesis of CuH(2)(-) in solid compounds has potential for use in hydrogen storage.

Infrared Spectra and Structures of the Stable CuH2-, AgH2-, AuH2-, and AuH4- Anions and the AuH2 Molecule

The hydrogen‐bonded complexes OC–HX (X=F, Cl, Br) has been prepared by condensing Ar/HX and Ar/CO reagent mixtures at 12 K. FTIR spectra of the complexes are characterized by strong H–X absorptions (νs) displaced below the isolated HX fundamental, strong C–O absorptions displaced above the isolated CO fundamental, and sharp degenerate librational modes (νl) in the far infrared. Observation of a single degenerate νl mode indicates linear structures for the complexes. The displacements Δνs and ΔνCO for the complexes decrease in magnitude in the series HF≳HCl≳HBr in direct relationship with the trend in hydrogen bonding strength for the hydrohalic acids.

Lester Andrews

Papers

Raman Spectra of the Products of Na and K Atom Argon Matrix Reactions with O2 Molecules

Matrix Infrared Spectra and Density Functional Calculations of Ni(CO)x-, x = 1−3

Infrared spectra and structures of isotopically enriched sulfur (S3 and S4) in solid argon

Infrared Spectra and Structures of the Stable CuH2-, AgH2-, AuH2-, and AuH4- Anions and the AuH2 Molecule

Infrared spectra of OC–HX hydrogen‐bonded complexes in solid argon