JCP Nameplate
  • Volume/Page
  • Keyword
  • DOI
  • Citation
  • Advanced
   
 
 
 

You Tube Flickr Twitter iResearch App Facebook

BROWSE VOLUMES

Year Range: 
Search Issue | RSS Feeds RSS
Previous Issue

28 Jun 2012

Volume 136, Issue 24, Articles (24xxxx)

Issue Cover Spotlight Figure

J. Chem. Phys. 136, 245101 (2012); http://dx.doi.org/10.1063/1.4729604 (10 pages)

Jacob I. Lewis, Devin J. Moss, and Thomas A. Knotts, IV
Enlarge Image | Read More
Page 1 of 3 Pages Next Page | Jump to Page
back to top
RSS Feeds
FREE

Communication: Probing non-equilibrium vibrational relaxation pathways of highly excited C≡N stretching modes following ultrafast back-electron transfer

Michael S. Lynch, Karla M. Slenkamp, and Munira Khalil

J. Chem. Phys. 136, 241101 (2012); http://dx.doi.org/10.1063/1.4731882 (4 pages)

Online Publication Date: 27 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Fifth-order nonlinear visible-infrared spectroscopy is used to probe coherent and incoherent vibrational energy relaxation dynamics of highly excited vibrational modes indirectly populated via ultrafast photoinduced back-electron transfer in a trinuclear cyano-bridged mixed-valence complex. The flow of excess energy deposited into four C≡N stretching (νCN) modes of the molecule is monitored by performing an IR pump-probe experiment as a function of the photochemical reaction (τvis). Our results provide experimental evidence that the nuclear motions of the molecule are both coherently and incoherently coupled to the electronic charge transfer process. We observe that intramolecular vibrational relaxation dynamics among the highly excited νCN modes change significantly en route to equilibrium. The experiment also measures a 7 cm−1 shift in the frequency of a ∼57 cm−1 oscillation reflecting a modulation of the coupling between the probed high-frequency νCN modes for τvis < 500 fs.
Show PACS
33.20.Tp Vibrational analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Ea Infrared spectra
33.20.Kf Visible spectra
FREE

Communication: Vibrational spectroscopy of atmospherically relevant acid cluster anions: Bisulfate versus nitrate core structures

Tara I. Yacovitch, Nadja Heine, Claudia Brieger, Torsten Wende, Christian Hock, Daniel M. Neumark, and Knut R. Asmis

J. Chem. Phys. 136, 241102 (2012); http://dx.doi.org/10.1063/1.4732148 (4 pages) | Cited 1 time

Online Publication Date: 28 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Infrared multiple photon dissociation spectra for the smallest atmospherically relevant anions of sulfuric and nitric acid allow us to characterize structures and distinguish between clusters with a bisulfate or a nitrate core. We find that bisulfate is the main charge carrier for HSO4−·H2SO4·HNO3 but not for NO3−·H2SO4·HNO3. For the mixed dimer anion, we find evidence for the presence of two isomers: HSO4−·HNO3 and NO3−·H2SO4. Density functional calculations accompany the experimental results and provide support for these observations.
Show PACS
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.80.Rv Multiphoton ionization and excitation to highly excited states (e.g., Rydberg states)
31.15.E- Density-functional theory
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)
33.20.Ea Infrared spectra
33.20.Tp Vibrational analysis
back to top
RSS Feeds
back to top Theoretical Methods and Algorithms

Investigation of the full configuration interaction quantum Monte Carlo method using homogeneous electron gas models

James J. Shepherd, George H. Booth, and Ali Alavi

J. Chem. Phys. 136, 244101 (2012); http://dx.doi.org/10.1063/1.4720076 (14 pages) | Cited 4 times

Online Publication Date: 22 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Using the homogeneous electron gas (HEG) as a model, we investigate the sources of error in the “initiator” adaptation to full configuration interaction quantum Monte Carlo (i-FCIQMC), with a view to accelerating convergence. In particular, we find that the fixed-shift phase, where the walker number is allowed to grow slowly, can be used to effectively assess stochastic and initiator error. Using this approach we provide simple explanations for the internal parameters of an i-FCIQMC simulation. We exploit the consistent basis sets and adjustable correlation strength of the HEG to analyze properties of the algorithm, and present finite basis benchmark energies for N = 14 over a range of densities 0.5 ⩽ rs ⩽ 5.0 a.u. A single-point extrapolation scheme is introduced to produce complete basis energies for 14, 38, and 54 electrons. It is empirically found that, in the weakly correlated regime, the computational cost scales linearly with the plane wave basis set size, which is justifiable on physical grounds. We expect the fixed-shift strategy to reduce the computational cost of many i-FCIQMC calculations of weakly correlated systems. In addition, we provide benchmarks for the electron gas, to be used by other quantum chemical methods in exploring periodic solid state systems.
Show PACS
71.10.Ca Electron gas, Fermi gas
71.45.Gm Exchange, correlation, dielectric and magnetic response functions, plasmons

Local unitary transformation method for large-scale two-component relativistic calculations: Case for a one-electron Dirac Hamiltonian

Junji Seino and Hiromi Nakai

J. Chem. Phys. 136, 244102 (2012); http://dx.doi.org/10.1063/1.4729463 (13 pages) | Cited 3 times

Online Publication Date: 22 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
An accurate and efficient scheme for two-component relativistic calculations at the spin-free infinite-order Douglas-Kroll-Hess (IODKH) level is presented. The present scheme, termed local unitary transformation (LUT), is based on the locality of the relativistic effect. Numerical assessments of the LUT scheme were performed in diatomic molecules such as HX and X2 (X = F, Cl, Br, I, and At) and hydrogen halide clusters, (HX)n (X = F, Cl, Br, and I). Total energies obtained by the LUT method agree well with conventional IODKH results. The computational costs of the LUT method are drastically lower than those of conventional methods since in the former there is linear-scaling with respect to the system size and a small prefactor.
Show PACS
31.30.jc Relativistic corrections to atomic structure and properties
36.90.+f Other topics in exotic atoms and molecules; macromolecules; clusters (restricted to new topics in section 36)

A long-range electrostatic potential based on the Wolf method charge-neutral condition

Yasushige Yonezawa

J. Chem. Phys. 136, 244103 (2012); http://dx.doi.org/10.1063/1.4729748 (8 pages) | Cited 3 times

Online Publication Date: 22 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Molecular simulations rely heavily on a long range electrostatic Coulomb interaction. The Coulomb potential decays inversely with distance, indicating infinite effective range. In practice, molecular simulations do not directly take into account such an infinite interaction. Therefore, the Ewald, fast multipole, and cutoff methods are frequently used. Although cutoff methods are implemented easily and the calculations are fast, it has been pointed out that they produce serious artifacts. Wolf and coworkers recently discovered one source of the artifacts. They found that when the total charge in a cutoff sphere disappeared, the cutoff error is dramatically suppressed. The Wolf method uses the charge-neutral principle combined with a potential damping that is realized using a complementary error function. To date, many molecular simulation studies have demonstrated the accuracy and reliability of the Wolf method. We propose a novel long-range potential that is constructed only from the charge-neutral condition of the Wolf method without potential damping. We also show that three simulation systems, in which involve liquid sodium-chloride, TIP3P water, and a charged protein in explicit waters with neutralized ions using the new potential, provide accurate statistical and dielectric properties when compared with the particle mesh Ewald method.
Show PACS
34.20.Cf Interatomic potentials and forces

Hierarchical transformation of Hamiltonians with linear and quadratic couplings for nonadiabatic quantum dynamics: Application to the ππ*/nπ* internal conversion in thymine

David Picconi, Alessandro Lami, and Fabrizio Santoro

J. Chem. Phys. 136, 244104 (2012); http://dx.doi.org/10.1063/1.4729049 (17 pages) | Cited 5 times

Online Publication Date: 25 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We face with the general problem of defining a reduced number of effective collective coordinates to describe accurately the short-time nonadiabatic dynamics of large semirigid systems, amenable to a description in terms of coupled harmonic potential energy surfaces. We present a numeric iterative protocol to define a hierarchical representation of the Hamiltonian taking into account both linear and quadratic intra- and inter-state couplings (QVC, quadratic vibronic coupling model), thus generalizing the method introduced recently in the literature [E. Gindensperger, H. Köppel, and L. S. Cederbaum, J. Chem. Phys. 126, 034106 (2007)]10.1063/1.2426342 for the linear vibronic coupling (LVC) model. This improvement allows to take into account the effect of harmonic frequency changes and Duschinsky mixings among the different electronic states, providing a route to upgrade the models for nonadiabatic harmonic systems to those nowadays routinely used for the simulation of vibronic spectra of adiabatic systems (negligible nonadiabatic couplings). We apply our method to the study of ππ* → nπ* internal conversion in thymine, analysing the differences in LVC and QVC predictions both for the absorption spectrum and the dynamics of electronic populations.
Show PACS
33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
31.50.-x Potential energy surfaces

Assessing the accuracy of quantum Monte Carlo and density functional theory for energetics of small water clusters

M. J. Gillan, F. R. Manby, M. D. Towler, and D. Alfè

J. Chem. Phys. 136, 244105 (2012); http://dx.doi.org/10.1063/1.4730035 (14 pages) | Cited 6 times

Online Publication Date: 25 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a detailed study of the energetics of water clusters (H2O)n with n ⩽ 6, comparing diffusion Monte Carlo (DMC) and approximate density functional theory (DFT) with well converged coupled-cluster benchmarks. We use the many-body decomposition of the total energy to classify the errors of DMC and DFT into 1-body, 2-body and beyond-2-body components. Using both equilibrium cluster configurations and thermal ensembles of configurations, we find DMC to be uniformly much more accurate than DFT, partly because some of the approximate functionals give poor 1-body distortion energies. Even when these are corrected, DFT remains considerably less accurate than DMC. When both 1- and 2-body errors of DFT are corrected, some functionals compete in accuracy with DMC; however, other functionals remain worse, showing that they suffer from significant beyond-2-body errors. Combining the evidence presented here with the recently demonstrated high accuracy of DMC for ice structures, we suggest how DMC can now be used to provide benchmarks for larger clusters and for bulk liquid water.
Show PACS
36.40.Sx Diffusion and dynamics of clusters
31.15.bw Coupled-cluster theory
31.15.E- Density-functional theory
33.15.Bh General molecular conformation and symmetry; stereochemistry

Complete nuclear motion Hamiltonian in the irreducible normal mode tensor operator formalism for the methane molecule

Michaël Rey, Andrei V. Nikitin, and Vladimir G. Tyuterev

J. Chem. Phys. 136, 244106 (2012); http://dx.doi.org/10.1063/1.4730030 (14 pages) | Cited 3 times

Online Publication Date: 26 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A rovibrational model based on the normal-mode complete nuclear Hamiltonian is applied to methane using our recent potential energy surface [A. V. Nikitin, M. Rey, and Vl. G. Tyuterev, Chem. Phys. Lett. 501, 179 (2011)10.1016/j.cplett.2010.11.008]. The kinetic energy operator and the potential energy function are expanded in power series to which a new truncation-reduction technique is applied. The vibration-rotation Hamiltonian is transformed systematically to a full symmetrized form using irreducible tensor operators. Each term of the Hamiltonian expansion can be thus cast in the tensor form whatever the order of the development. This allows to take full advantage of the symmetry properties for doubly and triply degenerate vibrations and vibration-rotation states. We apply this model to variational computations of energy levels for 12CH4, 13CH4, and 12CD4.
Show PACS
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
34.50.Ez Rotational and vibrational energy transfer
31.15.xt Variational techniques
31.50.-x Potential energy surfaces
33.15.Mt Rotation, vibration, and vibration-rotation constants

The dispersion interaction between quantum mechanics and effective fragment potential molecules

Quentin A. Smith, Klaus Ruedenberg, Mark S. Gordon, and Lyudmila V. Slipchenko

J. Chem. Phys. 136, 244107 (2012); http://dx.doi.org/10.1063/1.4729535 (12 pages) | Cited 2 times

Online Publication Date: 26 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
A method for calculating the dispersion energy between molecules modeled with the general effective fragment potential (EFP2) method and those modeled using a full quantum mechanics (QM) method, e.g., Hartree-Fock (HF) or second-order perturbation theory, is presented. C6 dispersion coefficients are calculated for pairs of orbitals using dynamic polarizabilities from the EFP2 portion, and dipole integrals and orbital energies from the QM portion of the system. Dividing by the sixth power of the distance between localized molecular orbital centroids yields the first term in the commonly employed London series expansion. A C8 term is estimated from the C6 term to achieve closer agreement with symmetry adapted perturbation theory values. Two damping functions for the dispersion energy are evaluated. By using terms that are already computed during an ordinary HF or EFP2 calculation, the new method enables accurate and extremely rapid evaluation of the dispersion interaction between EFP2 and QM molecules.
Show PACS
31.15.xp Perturbation theory
31.70.Dk Environmental and solvent effects
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
34.20.Gj Intermolecular and atom-molecule potentials and forces
Author Select

Local relativistic exact decoupling

Daoling Peng and Markus Reiher

J. Chem. Phys. 136, 244108 (2012); http://dx.doi.org/10.1063/1.4729788 (11 pages) | Cited 3 times

Online Publication Date: 27 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We present a systematic hierarchy of approximations for local exact decoupling of four-component quantum chemical Hamiltonians based on the Dirac equation. Our ansatz reaches beyond the trivial local approximation that is based on a unitary transformation of only the atomic block-diagonal part of the Hamiltonian. Systematically, off-diagonal Hamiltonian matrix blocks can be subjected to a unitary transformation to yield relativistically corrected matrix elements. The full hierarchy is investigated with respect to the accuracy reached for the electronic energy and for selected molecular properties on a balanced test molecule set that comprises molecules with heavy elements in different bonding situations. Our atomic (local) assembly of the unitary exact-decoupling transformation—called local approximation to the unitary decoupling transformation (DLU)—provides an excellent local approximation for any relativistic exact-decoupling approach. Its order-N2 scaling can be further reduced to linear scaling by employing a neighboring-atomic-blocks approximation. Therefore, DLU is an efficient relativistic method well suited for relativistic calculations on large molecules. If a large molecule contains many light atoms (typically hydrogen atoms), the computational costs can be further reduced by employing a well-defined nonrelativistic approximation for these light atoms without significant loss of accuracy. We also demonstrate that the standard and straightforward transformation of only the atomic block-diagonal entries in the Hamiltonian—denoted diagonal local approximation to the Hamiltonian (DLH) in this paper—introduces an error that is on the order of the error of second-order Douglas–Kroll–Hess (i.e., DKH2) when compared with exact-decoupling results. Hence, the local DLH approximation would be pointless in an exact-decoupling framework, but can be efficiently employed in combination with the fast to evaluate DKH2 Hamiltonian in order to speed up calculations for which ultimate accuracy is not the major concern.
Show PACS
31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
31.15.E- Density-functional theory
33.15.Bh General molecular conformation and symmetry; stereochemistry

De-perturbative corrections for charge-stabilized double ionization potential equation-of-motion coupled-cluster method

Tomasz Kuś and Anna I. Krylov

J. Chem. Phys. 136, 244109 (2012); http://dx.doi.org/10.1063/1.4730296 (10 pages) | Cited 1 time

Online Publication Date: 27 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Charge stabilization improves the numeric performance of double ionization potential equation-of-motion (EOM-DIP) method when using unstable (autoionizing) dianion references. However, the stabilization potential introduces an undesirable perturbation to the target states’ energies. Here we introduce and benchmark two approaches for removing the perturbation caused by the stabilization. The benchmark calculations of excitation energies in selected diradicals illustrate that the so-called core correction based on evaluating the perturbation in a small basis set is robust and yields reliable EOM-DIP values, i.e., the errors of 0.0–0.3 eV against a similar-level coupled-cluster approach.
Show PACS
31.15.bw Coupled-cluster theory
33.80.Eh Autoionization, photoionization, and photodetachment
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Dynamical (e,2e) studies of tetrahydrofurfuryl alcohol

S. M. Bellm, J. D. Builth-Williams, D. B. Jones, Hari Chaluvadi, D. H. Madison, C. G. Ning, F. Wang, X. G. Ma, B. Lohmann, and M. J. Brunger

J. Chem. Phys. 136, 244301 (2012); http://dx.doi.org/10.1063/1.4729466 (7 pages) | Cited 1 time

Online Publication Date: 22 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Cross section data for electron scattering from DNA are important for modelling radiation damage in biological systems. Triply differential cross sections for the electron impact ionization of the highest occupied outer valence orbital of tetrahydrofurfuryl alcohol, which can be considered as an analogue to the deoxyribose backbone molecule in DNA, have been measured using the (e,2e) technique. The measurements have been performed with coplanar asymmetric kinematics at an incident electron energy of 250 eV, an ejected electron energy of 20 eV, and at scattered electron angles of −5°, −10°, and −15°. Experimental results are compared with corresponding theoretical calculations performed using the molecular 3-body distorted wave model. Some important differences are observed between the experiment and calculations.
Show PACS
34.80.Gs Molecular excitation and ionization
82.39.Jn Charge (electron, proton) transfer in biological systems
87.50.-a Effects of electromagnetic and acoustic fields on biological systems
87.14.gk DNA

Prediction of the existence of the N2H− molecular anion

François Lique, Philippe Halvick, Thierry Stoecklin, and Majdi Hochlaf

J. Chem. Phys. 136, 244302 (2012); http://dx.doi.org/10.1063/1.4730036 (5 pages) | Cited 1 time

Online Publication Date: 25 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We predict the existence of the N2H− anion from first principle calculations. We present the three-dimensional potential energy surface and the bound states of the N2H−/D− van der Waals anion. The electronic calculations were performed using state-of-the-art ab initio methods and the nuclear motions were solved using a quantum close-coupling scattering theory. A T-shaped equilibrium structure was found, with a well depth of 349.1 cm−1, where 18 bound states have been located for N2H− and 25 for N2D− for total angular momentum J = 0. We also present the absorption spectra of the N2H− complex. This anion could be formed after low energy collisions between N2 and H− through radiative association. The importance of this prediction in astrophysics and the possible use of N2H− as a tracer of N2 and H− in the interstellar medium is discussed.
Show PACS
31.15.ae Electronic structure and bonding characteristics
31.50.-x Potential energy surfaces
34.20.Cf Interatomic potentials and forces
34.50.Lf Chemical reactions
82.30.Nr Association, addition, insertion, cluster formation
95.30.Ft Molecular and chemical processes and interactions

Ab initio calculations of the lowest electronic states in the CuNO system

B. Murali Krishna and Roberto Marquardt

J. Chem. Phys. 136, 244303 (2012); http://dx.doi.org/10.1063/1.4728155 (12 pages)

Online Publication Date: 25 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The lowest singlet and triplet electronic levels of the A′ and A″ symmetry species of the neutral copper-nitrosyl (CuNO) system are calculated by ab initio methods at the multi-reference configuration interaction (MRCI) level of theory with single and double excitations, and at the coupled cluster level of theory with both perturbational (CCSD(T)) and full inclusion of triple excitations (CCSDT). Experimental data are difficult to obtain, hence the importance of carrying out calculations as accurate as possible to address the structure and dynamics of this system. This paper aims at validating a theoretical protocol to develop global potential energy surfaces for transition metal nitrosyl complexes. For the MRCI calculations, the comparison of level energies at linear structures and their values from C2v and Cs symmetry restricted calculations has allowed to obtain clear settings regarding atomic basis sizes, active orbital spaces and roots obtained at the multi-configurational self-consistent field (MCSCF) level of theory. It is shown that a complete active space involving 18 valence electrons, 11 molecular orbitals and the prior determination of 12 roots in the MCSCF calculation is needed for overall qualitatively correct results from the MRCI calculations. Atomic basis sets of the valence triple-zeta type are sufficient. The present calculations yield a bound singlet A′ ground state for CuNO. The CCSD(T) calculations give a quantitatively more reliable account of electronic correlation close to equilibrium, while the MRCI energies allow to ensure the qualitative assessment needed for global potential energy surfaces. Relativistic coupled cluster calculations using the Douglas-Kroll-Hess Hamiltonian yield a dissociation energy of CuNO into Cu and NO to be (59 ± 5) kJ mol−1 ((4940 ± 400) hc cm−1). Favorable comparison is made with some of previous theoretical results and a few known experimental data.
Show PACS
31.15.am Relativistic configuration interaction (CI) and many-body perturbation calculations
31.15.bw Coupled-cluster theory
31.15.xp Perturbation theory
31.15.xr Self-consistent-field methods
31.50.Df Potential energy surfaces for excited electronic states
31.50.Bc Potential energy surfaces for ground electronic states

Binary and ternary recombination of para-H3+ and ortho-H3+ with electrons: State selective study at 77–200 K

Petr Dohnal, Michal Hejduk, Jozef Varju, Peter Rubovič, Štěpán Roučka, Tomáš Kotrík, Radek Plašil, Juraj Glosík, and Rainer Johnsen

J. Chem. Phys. 136, 244304 (2012); http://dx.doi.org/10.1063/1.4730162 (14 pages) | Cited 3 times

Online Publication Date: 26 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Measurements in H3+ afterglow plasmas with spectroscopically determined relative abundances of H3+ ions in the para-nuclear and ortho-nuclear spin states provide clear evidence that at low temperatures (77–200 K) para-H3+ ions recombine significantly faster with electrons than ions in the ortho state, in agreement with a recent theoretical prediction. The cavity ring-down absorption spectroscopy used here provides an in situ determination of the para/ortho abundance ratio and yields additional information on the translational and rotational temperatures of the recombining ions. The results show that H3+ recombination with electrons occurs by both binary recombination and third-body (helium) assisted recombination, and that both the two-body and three-body rate coefficients depend on the nuclear spin states. Electron-stabilized (collisional-radiative) recombination appears to make only a small contribution.
Show PACS
34.80.Lx Recombination, attachment, and positronium formation
52.80.Hc Glow; corona
33.15.Mt Rotation, vibration, and vibration-rotation constants

From strong van der Waals complexes to hydrogen bonding: From CO⋯H2O to CS⋯H2O and SiO⋯H2O complexes

Yan Zhang, David S. Hollman, and Henry F. Schaeffer, III

J. Chem. Phys. 136, 244305 (2012); http://dx.doi.org/10.1063/1.4730298 (7 pages)

Online Publication Date: 26 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Structures and interaction energies of complexes valence isoelectronic to the important CO⋯H2O complex, namely SiO⋯H2O and CS⋯H2O, have been studied for the first time using high-level ab initio methods. Although CO, SiO, and CS are valence isoelectronic, the structures of their complexes with water differ significantly, owing partially to their widely varied dipole moments. The predicted dissociation energies D0 are 1.8 (CO⋯H2O), 2.7 (CS⋯H2O), and 4.9 (SiO⋯H2O) kcal/mol. The implications of these results have been examined in light of the dipole moments of the separate moieties and current concepts of hydrogen bonding. It is hoped that the present results will spark additional interest in these complexes and in the general non-covalent paradigms they represent.
Show PACS
34.20.Gj Intermolecular and atom-molecule potentials and forces
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
33.15.Fm Bond strengths, dissociation energies
31.15.ae Electronic structure and bonding characteristics

Ab initio determination of the ionization potentials of water clusters (H2O)n (n = 2−6)

Javier Segarra-Martí, Manuela Merchán, and Daniel Roca-Sanjuán

J. Chem. Phys. 136, 244306 (2012); http://dx.doi.org/10.1063/1.4730301 (11 pages) | Cited 3 times

Online Publication Date: 26 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High-level quantum-chemical ab initio coupled-cluster and multiconfigurational perturbation methods have been used to compute the vertical and adiabatic ionization potentials of several water clusters: dimer, trimer, tetramer, pentamer, hexamer book, hexamer ring, hexamer cage, and hexamer prism. The present results establish reference values at a level not reported before for these systems, calibrating different computational strategies and helping to discard less reliable theoretical and experimental data. The systematic study with the increasing size of the water cluster allows obtaining some clues on the structure and reductive properties of liquid water.
Show PACS
31.15.bw Coupled-cluster theory
36.40.Mr Spectroscopy and geometrical structure of clusters
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
31.15.am Relativistic configuration interaction (CI) and many-body perturbation calculations

The I2 dissociation mechanisms in the chemical oxygen-iodine laser revisited

K. Waichman, B. D. Barmashenko, and S. Rosenwaks

J. Chem. Phys. 136, 244307 (2012); http://dx.doi.org/10.1063/1.4729948 (7 pages) | Cited 1 time

Online Publication Date: 27 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The recently suggested mechanism of I2 dissociation in the chemical oxygen-iodine laser (COIL) [K. Waichman, B. D. Barmashenko, and S. Rosenwaks, J. Appl. Phys. 106, 063108 (2009)10.1063/1.3213380; K. Waichman, B. D. Barmashenko, and S. Rosenwaks, J. Chem. Phys. 133, 084301 (2010)]10.1063/1.3480397 was largely based on the suggestion of V. N. Azyazov, S. Yu. Pichugin, and M. C. Heaven [J. Chem. Phys. 130, 104306 (2009)]10.1063/1.3081454 that the vibrational population of O2(a) produced in the chemical generator is high enough to play an essential role in the dissociation. The results of model calculations based on this mechanism agreed very well with measurements of the small signal gain g, I2 dissociation fraction F, and temperature T in the COIL. This mechanism is here revisited, following the recent experiments of M. V. Zagidullin [Quantum Electron. 40, 794 (2010)]10.1070/QE2010v040n09ABEH014357 where the observed low population of O2(b, v = 1) led to the conclusion that the vibrational population of O2(a) at the outlet of the generator is close to thermal equilibrium value. This value corresponds to a very small probability, ∼0.05, of O2(a) energy pooling to the states O2(X,a,b, v > 0). We show that the dissociation mechanism can reproduce the experimentally observed values of g, F, and T in the COIL only if most of the energy released in the processes of O2(a) energy pooling and O2(b) quenching by H2O ends up as vibrational energy of the products, O2(X,a,b), where the vibrational states v = 2 and 3 are significantly populated. We discuss possible reasons for the differences in the suggested vibrational population and explain how these differences can be reconciled.
Show PACS
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.15.Fm Bond strengths, dissociation energies
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Tp Vibrational analysis
33.50.Hv Radiationless transitions, quenching

Stark coefficients for highly excited rovibrational states of H2O

M. Grechko, O. Aseev, T. R. Rizzo, N. F. Zobov, L. Lodi, J. Tennyson, O. L. Polyansky, and O. V. Boyarkin

J. Chem. Phys. 136, 244308 (2012); http://dx.doi.org/10.1063/1.4730295 (8 pages)

Online Publication Date: 27 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Quantum beat spectroscopy is combined with triple-resonance vibrational overtone excitation to measure the Stark coefficients (SCs) of the water molecule for 28 rovibrational levels lying from 27 600 to 41 000 cm−1. These data provide a stringent test for assessing the accuracy of the available potential energy surfaces (PESs) and dipole moment surfaces (DMSs) of this benchmark molecule in this energy region, which is inaccessible by direct absorption. SCs, calculated using the combination of a high accuracy, spectroscopically determined PES and a recent ab initio DMS, are within the 1% accuracy of available experimental data for levels below 25 000 cm−1, and within 4.5% for coefficients associated with levels up to 35 000 cm−1. However, the error in the computed coefficients is over 60% for the very high rovibrational states lying just below the lowest dissociation threshold, due, it seems, to lack of a high accuracy PES in this region. The comparative analysis suggests further steps, which may bring the theoretical predictions closer to the experimental accuracy.
Show PACS
33.57.+c Magneto-optical and electro-optical spectra and effects
33.20.Vq Vibration-rotation analysis
33.15.Mt Rotation, vibration, and vibration-rotation constants
31.50.Df Potential energy surfaces for excited electronic states
33.15.Fm Bond strengths, dissociation energies
33.20.Tp Vibrational analysis

Accurate theoretical study of PSq (q = 0,+1,−1) in the gas phase

Saida Ben Yaghlane, Joseph S. Francisco, and Majdi Hochlaf

J. Chem. Phys. 136, 244309 (2012); http://dx.doi.org/10.1063/1.4730303 (11 pages) | Cited 1 time

Online Publication Date: 27 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
Highly correlated ab initio methods were used in order to generate the potential energy curves and spin-orbit couplings of electronic ground and excited states of PS and PS+. We also computed those of the bound parts of the electronic states of the PS− anion. We used standard coupled cluster CCSD(T) level with augmented correlation-consistent basis sets, internally contacted multi-reference configuration interaction, and the newly developed CCSD(T)-F12 methods in connection with the explicitly correlated basis sets. Core-valence correction and scalar relativistic effects were examined. Our data consist of a set of spectroscopic parameters (equilibrium geometries, harmonic vibrational frequencies, rotational constants, spin-orbit, and spin-spin constants), adiabatic ionization energies, and electron affinities. For the low laying electronic states, our calculations are consistent with previous works whereas the high excited states present rather different shapes. Based on these new computations, the earlier ultraviolet bands of PS and PS+ were reassigned. For PS− and in addition to the already known anionic three bound electronic states (i.e., X3Σ−, 1Δ, and 11Σ+), our calculations show that the 1Σ−, 3Σ+, and the 3Δ states are energetically below their quartet parent neutral state (a4Π). The depletion of the J = 3 component of PS−(3Δ) will mainly occur via weak interactions with the electron continuum wave.
Show PACS
31.15.aj Relativistic corrections, spin-orbit effects, fine structure; hyperfine structure
31.15.am Relativistic configuration interaction (CI) and many-body perturbation calculations
31.50.Bc Potential energy surfaces for ground electronic states
31.50.Df Potential energy surfaces for excited electronic states
31.15.bw Coupled-cluster theory
33.15.Bh General molecular conformation and symmetry; stereochemistry

The microwave and millimeter spectrum of ZnCCH (math2Σ+): A new zinc-containing free radical

J. Min (闵洁), D. T. Halfen, M. Sun, B. Harris, and L. M. Ziurys

J. Chem. Phys. 136, 244310 (2012); http://dx.doi.org/10.1063/1.4729943 (10 pages) | Cited 2 times

Online Publication Date: 28 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The pure rotational spectrum of the ZnCCH (math2Σ+) radical has been measured using Fourier transform microwave (FTMW) and millimeter direct-absorption methods in the frequency range of 7–260 GHz. This work is the first study of ZnCCH by any type of spectroscopic technique. In the FTMW system, the radical was synthesized in a mixture of zinc vapor and 0.05% acetylene in argon, using a discharge assisted laser ablation source. In the millimeter-wave spectrometer, the molecule was created from the reaction of zinc vapor, produced in a Broida-type oven, with pure acetylene in a dc discharge. Thirteen rotational transitions were recorded for the main species, 64ZnCCH, and between 4 and 10 for the 66ZnCCH, 68ZnCCH, 64ZnCCD, and 64Zn13C13CH isotopologues. The fine structure doublets were observed in all the data, and in the FTMW spectra, hydrogen, deuterium, and carbon-13 hyperfine splittings were resolved. The data have been analyzed with a 2Σ Hamiltonian, and rotational, spin-rotation, and H, D, and 13C hyperfine parameters have been established for this radical. From the rotational constants, an rm(1) structure was determined with rZn-C = 1.9083 Å, rC-C = 1.2313 Å, and rC-H = 1.0508 Å. The geometry suggests that ZnCCH is primarily a covalent species with the zinc atom singly bonded to the C≡C—H moiety. This result is consistent with the hyperfine parameters, which suggest that the unpaired electron is localized on the zinc nucleus. The spin-rotation constant indicates that an excited 2Π state may exist ∼19 000 cm−1 in energy above the ground state.
Show PACS
33.20.Bx Radio-frequency and microwave spectra
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.15.Fm Bond strengths, dissociation energies
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.15.Pw Fine and hyperfine structure

Theoretical study of the spectroscopically relevant parameters for the detection of HNPq and HPNq (q = 0, +1, −1) in the gas phase

Majdi Hochlaf, Roberto Linguerri, Shakeel S. Dalal, and Joseph S. Francisco

J. Chem. Phys. 136, 244311 (2012); http://dx.doi.org/10.1063/1.4730299 (10 pages) | Cited 2 times

Online Publication Date: 28 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
High level ab initio electronic structure calculations at different levels of theory have been performed on HNP and HPN neutrals, anions, and cations. This includes standard coupled cluster CCSD(T) level with augmented correlation-consistent basis sets, internally contacted multi-reference configuration interaction, and the newly developed CCSD(T)-F12 methods in connection with the explicitly correlated basis sets. Core–valence correction and scalar relativistic effects were examined. We present optimized equilibrium geometries, harmonic vibrational frequencies, rotational constants, adiabatic ionization energies, electron affinities, vertical detachment energies, and relative energies. In addition, the three-dimensional potential energy surfaces of HNP−1,0,+1 and of HPN−1,0,+1 were generated at the (R)CCSD(T)-F12b/cc-pVTZ-F12 level. The anharmonic terms and fundamentals were derived using second order perturbation theory. For HNP, our best estimate for the adiabatic ionization energy is 7.31 eV, for the adiabatic electron affinity is 0.47 eV. The higher energy isomer, HPN, is 23.23 kcal/mol above HNP. HPN possesses a rather large adiabatic electron affinity of 1.62 eV. The intramolecular isomerization pathways were computed. Our calculations show that HNP− to HPN− reaction is subject to electron detachment.
Show PACS
31.15.am Relativistic configuration interaction (CI) and many-body perturbation calculations
31.15.bw Coupled-cluster theory
31.50.-x Potential energy surfaces
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
31.30.J- Relativistic and quantum electrodynamic (QED) effects in atoms, molecules, and ions
34.50.Gb Electronic excitation and ionization of molecules

Collision-induced dissociation in (He, H2+(v = 0–2; j = 0–3)) system: A time-dependent quantum mechanical investigation

Sujitha Kolakkandy, Kousik Giri, and N. Sathyamurthy

J. Chem. Phys. 136, 244312 (2012); http://dx.doi.org/10.1063/1.4729255 (5 pages) | Cited 1 time

Online Publication Date: 29 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The collision-induced process He +H2+(v = 0–2;j = 0–3)→ He +H+H+ has been investigated using a time-dependent quantum mechanical wave packet approach, within the centrifugal sudden approximation. The exchange reaction He + H2+ → HeH+ + H, which has a lower threshold, dominates over the dissociation process over the entire energy range considered in this study. The reaction cross section for both the exchange and dissociation channels and the branching ratio between the two channels have been computed on the McLaughlin-Thompson-Joseph-Sathyamurthy potential-energy surface and compared with the available experimental and quasiclassical trajectory results.
Show PACS
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
34.50.Ez Rotational and vibrational energy transfer
34.50.Lf Chemical reactions
82.20.Kh Potential energy surfaces for chemical reactions
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)

Can density functional theory describe the NO(X2Π)-Ar and NO(A2Σ+)-Ar van der Waals complexes?

Olga V. Ershova and Nicholas A. Besley

J. Chem. Phys. 136, 244313 (2012); http://dx.doi.org/10.1063/1.4730302 (9 pages) | Cited 2 times

Online Publication Date: 29 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
The interaction of nitric oxide (NO) in its ground state X2Π and the first excited Rydberg state A2Σ+ with an argon (Ar) atom has been studied using density functional theory. A number of exchange-correlation functionals that account for dispersion interactions have been considered, including functionals with both empirical and non-empirical treatments of dispersion. To study NO in the excited state, the recently developed maximum overlap method was used. Potential energy surfaces for interaction of NO with Ar have been constructed and parameters describing their minima, such as NO-Ar distance, orientation angle, and binding energy, have been determined. A comparison with combined experimental and accurate theoretical data has been made in terms of these parameters and the overall shape of the surfaces. For the ground state, several of the functionals give very good results. Treatment of the excited state is more problematic. None of the functionals considered provides completely satisfactory results. Several reasons for this failure have been identified: an incorrect description of the non-dispersion component of the interaction and the damping of the dispersion interaction at small interatomic distances.
Show PACS
31.15.eg Exchange-correlation functionals (in current density functional theory)
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
34.20.Gj Intermolecular and atom-molecule potentials and forces
31.50.Df Potential energy surfaces for excited electronic states
34.50.Cx Elastic; ultracold collisions
back to top Condensed Phase Dynamics, Structure, and Thermodynamics: Spectroscopy, Reactions, and Relaxation

Ionic liquids as oxidic media for electron transfer studies

Kazuhide Ueno and C. Austen Angell

J. Chem. Phys. 136, 244501 (2012); http://dx.doi.org/10.1063/1.4729306 (7 pages)

Online Publication Date: 25 June 2012

Full Text: Read Online (HTML) | Download PDF

Show Abstract
We review the basic ideas underlying the electron free energy level diagrams that have been found useful in considering the thermodynamics of redox processes in molten silicates and related high temperature ionic liquid (IL) solvents, and then show how closely they link to behavior observable in ambient temperature ionic liquids. Much of the information available on redox levels in molten oxides has been gleaned from chemical analysis and spectroscopic species distribution studies, but it is simpler to obtain the data electrochemically. Here, we report some cyclic voltammetry measurements of the Fe(II)/Fe(III) redox equilibrium in aprotic ionic liquids whose anions provide oxide environments for the redox species that are of different electronic polarizability character from the high temperature solvents, and relate the observations to those of the earlier studies. Quasi-reversible behavior is found in each of the cases studied. As might be expected, the Fe(II)/Fe(III) equilibrium experiences a more basic environment in an acetate IL than it experiences in any of the common glassforming oxide media, while triflate anions contrast by providing a more acid environment than does the most acid of the molten oxide glassformers studied (an alkali phosphate). The difference can amount to well over 1 V, suggesting the possibility of a “basicity cell” where the same redox couple locates in anode and cathode compartments of the cell, and only the anion environment is different.
Show PACS
82.45.Rr Electroanalytical chemistry
82.60.Hc Chemical equilibria and equilibrium constants
31.70.Dk Environmental and solvent effects
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
82.20.Yn Solvent effects on reactivity
82.45.Fk Electrodes
Page 1 of 3 Pages Next Page | Jump to Page
Close

Google Calendar

ADVERTISEMENT

Go to AIP Home   © AIP Publishing LLC
close