scispace - formally typeset
Search or ask a question
Author

Lester Andrews

Bio: Lester Andrews is an academic researcher from University of Virginia. The author has contributed to research in topics: Infrared spectroscopy & Molecule. The author has an hindex of 68, co-authored 888 publications receiving 24613 citations. Previous affiliations of Lester Andrews include Ames Research Center & Environmental Molecular Sciences Laboratory.


Papers
More filters
Journal ArticleDOI
TL;DR: Based on density functional theory calculations of structures and vibrational frequencies, the 2130.8 and 1274.4 cm−1 bands were assigned to the C2O4+ cation with C2h symmetry, and the 1852.4, 1189.2, and 679.2 cm− 1 bands were allocated to the (CO2−)(CO2)x(x=1,2) anion complexes.
Abstract: Laser ablation of transition metal targets with concurrent 4 K codeposition of CO2/Ne mixtures produces metal independent infrared absorptions at 1658.2 and 1421.6 cm−1 due to CO2− and CO2+. Additional metal independent absorptions at 2130.8 and 1274.4 cm−1, and at 1852.4, 1189.2, and 679.2 cm−1 increase on annealing to 8 K. Isotopic substitution shows that both band sets involve two equivalent CO2 subunits. Based on density functional theory calculations of structures and vibrational frequencies, the 2130.8 and 1274.4 cm−1 bands are assigned to the C2O4+ cation with C2h symmetry, and the 1852.4, 1189.2, and 679.2 cm−1 bands are assigned to the C2O4− anion with D2d symmetry. Evidence is also obtained for (CO2−)(CO2)x(x=1,2) anion complexes.

46 citations

Journal ArticleDOI
TL;DR: In this paper, laser-ablated vanadium and titanium atoms were reacted with CO molecules during condensation in excess neon, and the V(CO)x and Ti(COx)x (x = 1−6) molecules were formed during deposition or on annealing and photolysis.
Abstract: Laser-ablated vanadium and titanium atoms were reacted with CO molecules during condensation in excess neon. The V(CO)x and Ti(CO)x (x = 1−6) molecules are formed during deposition or on annealing and photolysis. The V(CO)x-, Ti(CO)x- (x = 1−6) anions and TiCO+ cation are also produced and identified on the basis of isotopic substitution and density functional calculations. Selective photolysis and CCl4 doping experiments strongly support the identification of the anions and cation.

46 citations

Journal ArticleDOI
TL;DR: In this article, infrared spectra have been observed for several group V base-HX (X=F, Cl) hydrogen bonded complexes formed by codeposition of Ar/base and Ar/HX samples.
Abstract: Infrared spectra have been observed for several group V base–HX (X=F, Cl) hydrogen bonded complexes formed by codeposition of Ar/base and Ar/HX samples. The decrease in displacement of the H–X stretching fundamentals for the heavier bases parallels a similar decrease in base proton affinities, indicating decreasing hydrogen bond strengths. A single, sharp degenerate librational mode was observed, which indicates C3v structures for the complexes. The decrease in librational fundamentals observed in the order PH3>AsH3>SbH3 and decreasing 2νl/νl ratios indicate increasing anharmonicity and less rigid structures for the heavier complexes. Polarization of the phosphine lone pair and concentration of the P‐H bonding electrons is suggested by blue‐shifted νc3 and νc1 complex modes. OFF

45 citations

Journal ArticleDOI
TL;DR: In this article, the electronic and geometrical structure of FenCO, FenCO−, and FenCO+ (n=2-6) were computed using density functional theory (DFT), and several hybrid and pure DFT methods were tested on FeCO and Fe2CO where experimental data were available.
Abstract: The electronic and geometrical structure of the ground and excited states of FenCO, FenCO−, and FenCO+ (n=2–6) are computed using density functional theory (DFT). Several hybrid and pure DFT methods are tested on FeCO and Fe2CO where experimental data are available. The pure DFT methods are superior to hybrid methods in reproduction of experimental spectroscopic data, except for the dissociation energy of FeCO. CO is twofold coordinated in Fe2CO, Fe3CO, and Fe4CO, threefold coordinated in Fe5CO, and fourfold in Fe6CO. While the Boudouard-type disproportionation reaction FenCO+CO→FenC+CO2 is endothermic by 1.59, 1.10, and 0.55 eV for FeCO, Fe2CO, and Fe3CO, respectively, it becomes exothermic beginning with n=4. The reaction barrier decreases from 3.5 eV for FeCO to 1.3 eV for Fe4CO. The most exothermic (by 0.42 eV) reaction is Fe6CO++CO→Fe6C++CO2. It is found that the catalytic ability increases with clusters size due to the decreasing FenC–O (or increasing Fen–C) bond strength. The Fen–CO binding energy ...

45 citations


Cited by
More filters
Book
01 Sep 2001
TL;DR: A Chemist's Guide to Density Functional Theory should be an invaluable source of insight and knowledge for many chemists using DFT approaches to solve chemical problems.
Abstract: "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.

3,550 citations

Journal ArticleDOI
TL;DR: In this paper, the authors survey the local density functional formalism and some of its applications and discuss the reasons for the successes and failures of the local-density approximation and some modifications.
Abstract: 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.

3,285 citations

Journal ArticleDOI
TL;DR: 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.
Abstract: 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.

2,582 citations

Journal ArticleDOI
TL;DR: The detection methods and generation mechanisms of the intrinsic reactive oxygen species (ROS) in photocatalysis were surveyed comprehensively and the major photocatalyst used in heterogeneous photocatalytic systems was found to be TiO2.
Abstract: 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...

2,249 citations

01 Feb 1995
TL;DR: In this paper, the unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio using DFT, MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set.
Abstract: : 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

1,652 citations