The high concentrations of Cl and ClO over Antarctica during the austral spring is now well known to be due to the catalytic cycle for the destruction of ozone for which these species are participants. The equilibrium structures, vibrational spectra, and heats of formation for CH{sub 3}OCl and CH{sub 3}ClO have been estimated using high levels of ab initio molecular orbital theory. The lowest energy isomer is found to be CH{sub 3}OCl, and its heat of formation is estimated to be {minus}13.5 {+-} 2 kcal mol{sup {minus}1}, in good agreement with bond additivity estimates. Results for the CH{sub 3}ClO isomer are presented for the first time, and it is found to be 40.5 kcal mol{sup {minus}1} higher in energy relative to CH{sub 3}OCl.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTStructural and spectral consequences of ion pairing. 4. Theoretical study of alkali metal tetrafluoroborates (M+BF4-; M = lithium, sodium, potassium, and rubidium)Joseph S. Francisco and Ian H. WilliamsCite this: J. Phys. Chem. 1990, 94, 23, 8522–8529Publication Date (Print):November 1, 1990Publication History Published online1 May 2002Published inissue 1 November 1990https://pubs.acs.org/doi/10.1021/j100386a008https://doi.org/10.1021/j100386a008research-articleACS PublicationsRequest reuse permissionsArticle Views171Altmetric-Citations39LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts
The HOCO radical has a ground (X 2A′) and two lowest A″2 excited states that are located using the CCSD(T) level of theory with the cc-pVDZ and cc-pVTZ basis sets. The harmonic frequencies are calculated at the CCSD(T) level of theory with the cc-pVDZ basis set. The vertical excitation energies for the 2 2A′, 3 2A′, 1 2A″, and 2 2A″ states of HOCO are obtained at the MRCI level of theory with the cc-pVTZ and aug-cc-pVTZ basis sets. The first excited state (1 2A″) is calculated to be 70.7 kcal mol−1 above the ground state for trans-HOCO. Comparisons are made between the excited states of HOCO and HCO. It is demonstrated that the HOCO states are not similar to those of HCO.
ABSTRACT Using both standard and explicitly correlated ab initio methods in conjunction with several atomic basis sets, the ground state of AlO(X 2 Σ + ) and the two lowest electronic states of AlO + ( 1 Σ + and 3 Π) are investigated. Potential energy curves for these species are mapped, which are incorporated later to solve the nuclear motion problem. Benchmark computations on AlO(X 2 Σ + ) are used to determine the reliability of the theoretical methods and basis sets used for an accurate description of aluminum oxide compounds. The electronic ground state of AlO + is X 1 Σ + , followed by the low-lying 1 3 Π state. For both cationic electronic states, a set of spectroscopic parameters are recommended that may help in the identification of this ion in laboratory and astrophysical media. An accurate estimation of the adiabatic ionization energy of AlO, AIE = 9.70 eV, is also reported.
NiFe-layered double hydroxide (LDH) is thought of as a promising bifunctional water-splitting catalyst, owing to its excellent performances for alkaline oxygen evolution reactions (OERs). However, it shows extremely poor activity toward hydrogen evolution reactions (HERs) due to the weak hydrogen adsorption. We demonstrated that the integration of Rh species and NiFe-LDH can dramatically improve its HER kinetics without sacrificing the OER performance. The Rh species were initially integrated into NiFe-LDH as oxidized dopants and metallic clusters (< 1 nm). In 1 M KOH electrolyte, an overpotential of 58 mV is needed to catalyze 10 mA cm–2 HER current density. Furthermore, this catalyst only requires 1.46 V to drive an electrolyzer at 10 mA cm–2. A strong interaction between metallic Rh clusters and NiFe hydroxide during the HER process is revealed. The theoretical calculation shows the Rh ions replace Fe ions as the major active sites that are responsible for OERs.
ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTInfrared multiphoton decomposition and energy-dependent absorption cross section of chloroethaneJoseph S. Francisco, Warren D. Lawrance, Jeffrey I. Steinfeld, and Robert G. GilbertCite this: J. Phys. Chem. 1982, 86, 5, 724–728Publication Date (Print):March 1, 1982Publication History Published online1 May 2002Published inissue 1 March 1982https://pubs.acs.org/doi/10.1021/j100394a027https://doi.org/10.1021/j100394a027research-articleACS PublicationsRequest reuse permissionsArticle Views45Altmetric-Citations7LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail Other access options Get e-Alerts
Surfaces that exhibit both superhydrophobic and superoleophobic properties have recently been demonstrated. Specifically, remarkable designs based on overhanging/inverse-trapezoidal microstructures enable water droplets to contact these surfaces only at the tips of the micro-pillars, in a state known as the Cassie state. However, the Cassie state may transition into the undesirable Wenzel state under certain conditions. Herein, we show from large-scale molecular dynamics simulations that the transition between the Cassie and Wenzel states can be controlled via precisely designed trapezoidal nanostructures on a surface. Both the base angle of the trapezoids and the intrinsic contact angle of the surface can be exploited to control the transition. For a given base angle, three regimes can be achieved: the Wenzel regime, in which water droplets can exist only in the Wenzel state when the intrinsic contact angle is less than a certain critical value; the Cassie regime, in which water droplets can exist only in the Cassie state when the intrinsic contact angle is greater than another critical value; and the bistable Wenzel-Cassie regime, in which both the Wenzel and Cassie states can exist when the intrinsic contact angle is between the two critical values. A strong base-angle dependence of the first critical value is revealed, whereas the second critical value shows much less dependence on the base angle. The stability of the Cassie state for various base angles (and intrinsic contact angles) is quantitatively evaluated by computing the free-energy barrier for the Cassie-to-Wenzel state transition.
A new aluminum-bearing species, OAlNO, which has the potential to impact the chemistry of the Earth's upper atmosphere, is characterized via high-level, ab initio, spectroscopic methods. Meteor-ablated aluminum atoms are quickly oxidized to aluminum oxide (AlO) in the mesosphere and lower thermosphere (MLT), where a steady-state layer of AlO then builds up. Concurrent formation of nitric oxide (NO) in the same region of the atmosphere will lead to the bimolecular formation of the OAlNO molecule. Molecular orbital analysis provides fundamental insights into the chemical bonding and energetic arrangement of the triplet (1 3A″) ground state and singlet (1 1A') excited-state species of OAlNO. Additionally, unpaired electrons on the terminal oxygen atom of triplet (1 3A″) OAlNO cause it to be reactive to atmospheric species, potentially impacting climate science and high-altitude chemistry. The triplet (1 3A″) ground-state species exhibits a large permanent dipole moment useful for rotational spectroscopic detection; however, similar rotational constants to the singlet (1 1A') excited-state species will hamper differentiation in a spectrum. Strong infrared intensities will assist in detection and discrimination of the different spin states and isomers. Repulsive electronic excited states of OAlNO will lead to photolysis of the Al-N bond and formation of various electronic states of AlO + NO through nonadiabatic pathways. Reaction through the OAlNO intermediate represents a means for the production of electronically excited AlO, leading to new chemistry in the atmosphere. Excitation to higher-lying electronic states will lead to fluorescence with a minor Stokes shift, useful for laboratory investigation. Such physical properties of this molecule will allow for new, unexplored chemical pathways in the MLT to be considered.
Abstract We obtained accurate vibrational frequencies, rotational constants, and vertical transition energy for AlNH 2 (X 1 A 1 ) and HAlNH(X 1 A′) isomers using ab initio calculations at various levels of theory. These two isomers are potential candidates for astronomical observation. AlNH 2 and HAlNH are thermodynamically stable, with Al-NH 2 and HAl-NH bond dissociation energies predicted to be 4.39 and 3.60 eV, respectively. The two isomers are characterized by sizable dipole moments of 1.211 and 3.64 D, respectively. The anharmonic frequencies and spectroscopic constants reported for the two isomers should facilitate their experimental differentiation. In addition, we evaluated the evolution of the low-lying electronic states along the stretching coordinates, as well as the absorption cross sections. AlNH 2 absorbs strongly around 287, 249, and 200 nm, whereas the HAlNH absorption is centered around 370 and 233 nm.
Tandem mass spectrometry is used to show that low energy collisions of ionized halocarbenes, including CBr2•+ and CBrCl•+, with molecular oxygen lead to (i) decarbonation with formation of the dihalogen molecular cation and (ii) oxygenolysis yielding BrCO+. Both reactions may occur via the same ion−molecule addition product of molecular oxygen and the ionized carbene. Reaction is favored at low collision energies, such as are encountered in an ion trap. Insights into the energetics of the reactions of CBr2•+ with O2 are obtained from ab initio molecular orbital theory. Other aspects of the positive ion chemistry of dioxygen with various halogen-containing ions are also discussed. Dioxygen activation by halocarbon ions suggests additional channels that might affect the fate of halocarbons and the ozone balance in the atmosphere.
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