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28 Feb 2012

Volume 136, Issue 8, Articles (08xxxx)

Issue Cover Spotlight Figure

J. Chem. Phys. 136, 084102 (2012); http://dx.doi.org/10.1063/1.3685604 (13 pages)

Junchao Xia, Chen Huang, Ilgyou Shin, and Emily A. Carter
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Communication: Fundamental measure theory for hard disks: Fluid and solid

Roland Roth, Klaus Mecke, and Martin Oettel

J. Chem. Phys. 136, 081101 (2012); http://dx.doi.org/10.1063/1.3687921 (4 pages)

Online Publication Date: 22 February 2012

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Two-dimensional hard-particle systems are rather easy to simulate but surprisingly difficult to treat by theory. Despite their importance from both theoretical and experimental points of view, theoretical approaches are usually qualitative or at best semi-quantitative. Here, we present a density functional theory based on the ideas of fundamental measure theory for two-dimensional hard-disk mixtures, which allows for the first time an accurate description of the structure of the dense fluid and the equation of state for the solid phase within the framework of density functional theory. The properties of the solid phase are obtained by freely minimizing the functional.
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64.10.+h General theory of equations of state and phase equilibria
71.15.Mb Density functional theory, local density approximation, gradient and other corrections
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Communication: Identical temperature dependence of the time scales of several linear-response functions of two glass-forming liquids

Bo Jakobsen, Tina Hecksher, Tage Christensen, Niels Boye Olsen, Jeppe C. Dyre, and Kristine Niss

J. Chem. Phys. 136, 081102 (2012); http://dx.doi.org/10.1063/1.3690083 (4 pages)

Online Publication Date: 24 February 2012

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The frequency-dependent dielectric constant, shear and adiabatic bulk moduli, longitudinal thermal expansion coefficient, and longitudinal specific heat have been measured for two van der Waals glass-forming liquids, tetramethyl-tetraphenyl-trisiloxane (DC704) and 5-polyphenyl-4-ether. Within the experimental uncertainties the loss-peak frequencies of the measured response functions have identical temperature dependence over a range of temperatures, for which the Maxwell relaxation time varies more than nine orders of magnitude. The time scales are ordered from fastest to slowest as follows: Shear modulus, adiabatic bulk modulus, dielectric constant, longitudinal thermal expansion coefficient, and longitudinal specific heat. The ordering is discussed in light of the recent conjecture that van der Waals liquids are strongly correlating, i.e., approximate single-parameter liquids.
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64.70.pm Liquids
65.20.Jk Studies of thermodynamic properties of specific liquids
62.10.+s Mechanical properties of liquids
77.22.Ch Permittivity (dielectric function)
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back to top Theoretical Methods and Algorithms

Mapping quantum-classical Liouville equation: Projectors and trajectories

Aaron Kelly, Ramses van Zon, Jeremy Schofield, and Raymond Kapral

J. Chem. Phys. 136, 084101 (2012); http://dx.doi.org/10.1063/1.3685420 (14 pages)

Online Publication Date: 22 February 2012

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The evolution of a mixed quantum-classical system is expressed in the mapping formalism where discrete quantum states are mapped onto oscillator states, resulting in a phase space description of the quantum degrees of freedom. By defining projection operators onto the mapping states corresponding to the physical quantum states, it is shown that the mapping quantum-classical Liouville operator commutes with the projection operator so that the dynamics is confined to the physical space. It is also shown that a trajectory-based solution of this equation can be constructed that requires the simulation of an ensemble of entangled trajectories. An approximation to this evolution equation which retains only the Poisson bracket contribution to the evolution operator does admit a solution in an ensemble of independent trajectories but it is shown that this operator does not commute with the projection operators and the dynamics may take the system outside the physical space. The dynamical instabilities, utility, and domain of validity of this approximate dynamics are discussed. The effects are illustrated by simulations on several quantum systems.
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03.65.Ta Foundations of quantum mechanics; measurement theory
03.65.Ud Entanglement and quantum nonlocality (e.g. EPR paradox, Bell's inequalities, GHZ states, etc.)
05.45.Xt Synchronization; coupled oscillators
02.30.Rz Integral equations

Can orbital-free density functional theory simulate molecules?

Junchao Xia, Chen Huang, Ilgyou Shin, and Emily A. Carter

J. Chem. Phys. 136, 084102 (2012); http://dx.doi.org/10.1063/1.3685604 (13 pages)

Online Publication Date: 22 February 2012

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Orbital-free density functional theory (OFDFT), with its attractive linearly scaling computation cost and low prefactor, is one of the most powerful first principles methods for simulating large systems (∼104–106 atoms). However, approximating the electron kinetic energy with density functionals limits the accuracy and generality of OFDFT compared to Kohn-Sham density functional theory (KSDFT). In this work, we test whether the Huang-Carter (HC) kinetic energy density functional (KEDF), which contains the physics to properly describe covalently bonded semiconductor materials, can also be used to describe covalent bonds in molecules. In particular, we calculate a variety of homonuclear diatomic molecules with the HC functional within OFDFT. The OFDFT bond dissociation energy, equilibrium bond length, and vibrational frequency of these dimers are in remarkably good agreement with benchmark KSDFT results, given the lack of orbitals in the calculation. We vary the two parameters λ (controlling the reduced density gradient contribution to the nonlocal kernel) and β (the exponent of the density in the nonlocal term) present in the HC KEDF and find that the optimal λ correlates with the magnitude of the highest occupied molecular orbital - lowest unoccupied molecular orbital energy gap. Although the HC KEDF represents a significant improvement over previous KEDFs in describing covalent systems, deficiencies still exist. Despite the similar overall shape of the KSDFT and OFDFT ground state electron densities, the electron density within the bonding region is still quite different. Furthermore, OFDFT is not yet able to give reasonable description of magnetic states. The energy orderings of the triplet and singlet states of Si2 and Al family dimers are not consistent with KSDFT or experimental results and the spin polarization distributions also differ widely between the two theories.
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31.15.E- Density-functional theory
33.20.Tp Vibrational analysis
33.15.Fm Bond strengths, dissociation energies
33.15.Dj Interatomic distances and angles
31.15.ae Electronic structure and bonding characteristics

Non-Born-Oppenheimer electronic and nuclear densities for a Hooke-Calogero three-particle model: Non-uniqueness of density-derived molecular structure

E. V. Ludeña, L. Echevarría, X. Lopez, and J. M. Ugalde

J. Chem. Phys. 136, 084103 (2012); http://dx.doi.org/10.1063/1.3682244 (12 pages)

Online Publication Date: 24 February 2012

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We consider the calculation of non-Born-Oppenheimer, nBO, one-particle densities for both electrons and nuclei. We show that the nBO one-particle densities evaluated in terms of translationally invariant coordinates are independent of the wavefunction describing the motion of center of mass of the whole system. We show that they depend, however, on an arbitrary reference point from which the positions of the vectors labeling the particles are determined. We examine the effect that this arbitrary choice has on the topology of the one-particle density by selecting the Hooke-Calogero model of a three-body system for which expressions for the one-particle densities can be readily obtained in analytic form. We extend this analysis to the one-particle densities obtained from full Coulomb interaction wavefunctions for three-body systems. We conclude, in view of the fact that there is a close link between the choice of the reference point and the topology of one-particle densities that the molecular structure inferred from the topology of these densities is not unique. We analyze the behavior of one-particle densities for the Hooke-Calogero Born-Oppenheimer, BO, wavefunction and show that topological transitions are also present in this case for a particular mass value of the light particles even though in the BO regime the nuclear masses are infinite. In this vein, we argue that the change in topology caused by variation of the mass ratio between light and heavy particles does not constitute a true indication in the nBO regime of the emergence of molecular structure.
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03.65.Ta Foundations of quantum mechanics; measurement theory
03.65.Ge Solutions of wave equations: bound states

Reduced density matrix hybrid approach: Application to electronic energy transfer

Timothy C. Berkelbach, Thomas E. Markland, and David R. Reichman

J. Chem. Phys. 136, 084104 (2012); http://dx.doi.org/10.1063/1.3687342 (11 pages)

Online Publication Date: 27 February 2012

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Electronic energy transfer in the condensed phase, such as that occurring in photosynthetic complexes, frequently occurs in regimes where the energy scales of the system and environment are similar. This situation provides a challenge to theoretical investigation since most approaches are accurate only when a certain energetic parameter is small compared to others in the problem. Here we show that in these difficult regimes, the Ehrenfest approach provides a good starting point for a dynamical description of the energy transfer process due to its ability to accurately treat coupling to slow environmental modes. To further improve on the accuracy of the Ehrenfest approach, we use our reduced density matrix hybrid framework to treat the faster environmental modes quantum mechanically, at the level of a perturbative master equation. This combined approach is shown to provide an efficient and quantitative description of electronic energy transfer in a model dimer and the Fenna-Matthews-Olson complex and is used to investigate the effect of environmental preparation on the resulting dynamics.
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71.35.-y Excitons and related phenomena
82.50.-m Photochemistry

Basis set convergence of molecular correlation energy differences within the random phase approximation

Henk Eshuis and Filipp Furche

J. Chem. Phys. 136, 084105 (2012); http://dx.doi.org/10.1063/1.3687005 (6 pages)

Online Publication Date: 27 February 2012

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The basis set convergence of energy differences obtained from the random phase approximation (RPA) to the correlation energy is investigated for a wide range of molecular interactions. For dispersion bound systems the basis set incompleteness error is most pronounced, as shown for the S22 benchmark [P. Jurecka et al., Phys. Chem. Chem. Phys. 8, 1985 (2006)10.1039/b600027d]. The use of very large basis sets (> quintuple-zeta) or extrapolation to the complete basis set (CBS) limit is necessary to obtain a reliable estimate of the binding energy for these systems. Counterpoise corrected results converge to the same CBS limit, but counterpoise correction without extrapolation is insufficient. Core-valence correlations do not play a significant role. For medium- and short-range correlation, quadruple-zeta results are essentially converged, as demonstrated for relative alkane conformer energies, reaction energies dominated by intramolecular dispersion, isomerization energies, and reaction energies of small organic molecules. Except for weakly bound systems, diffuse augmentation almost universally slows down basis set convergence. For most RPA applications, quadruple-zeta valence basis sets offer a good balance between accuracy and efficiency.
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31.15.V- Electron correlation calculations for atoms, ions and molecules
82.30.Qt Isomerization and rearrangement
34.20.Gj Intermolecular and atom-molecule potentials and forces
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy

Temperature inhomogeneities simulated with multiparticle-collision dynamics

Daniel Lüsebrink and Marisol Ripoll

J. Chem. Phys. 136, 084106 (2012); http://dx.doi.org/10.1063/1.3687168 (9 pages)

Online Publication Date: 27 February 2012

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The mesoscopic simulation technique known as multiparticle collision dynamics is presented as a very appropriate method to simulate complex systems in the presence of temperature inhomogeneities. Three different methods to impose the temperature gradient are compared and characterized in the parameter landscape. Two methods include the interaction of the system with confining walls. The third method considers open boundary conditions by imposing energy fluxes. The transport of energy characterizing the thermal diffusivity is also investigated. The dependence of this transport coefficient on the method parameters and the accuracy of existing analytical theories is discussed.
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66.10.cd Thermal diffusion and diffusive energy transport
47.11.-j Computational methods in fluid dynamics

Canonical transcorrelated theory with projected Slater-type geminals

Takeshi Yanai and Toru Shiozaki

J. Chem. Phys. 136, 084107 (2012); http://dx.doi.org/10.1063/1.3688225 (9 pages)

Online Publication Date: 28 February 2012

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An effective Hamiltonian perturbed with explicit interelectronic correlation is derived from similarity transformation of Hamiltonian using a unitary operator with Slater-type geminals. The Slater-type geminal is projected onto the excitation (and deexcitation) component as in the F12 theory. Simplification is made by truncating higher-body operators, resulting in a correlated Hamiltonian which is Hermitian and has exactly the same complexity as the original Hamiltonian in the second quantized form. It can thus be easily combined with arbitrary correlation models proposed to date. The present approach constructs a singularity-free Hamiltonian a priori, similarly to the so-called transcorrelated theory, while the use of the canonical transformation assures that the effective Hamiltonian is two-body and Hermite. Our theory is naturally extensible to multireference calculations on the basis of the generalized normal ordering. The construction of the effective Hamiltonian is non-iterative. The numerical assessments demonstrate that the present scheme improves the basis set convergence of the post-mean-field calculations at a similar rate to the explicitly correlated methods proposed by others that couple geminals and conventional excitations.
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31.15.V- Electron correlation calculations for atoms, ions and molecules

Dynamic hyperpolarizability calculations of large systems: The linear-scaling divide-and-conquer approach

Masato Kobayashi, Tsuguki Touma, and Hiromi Nakai

J. Chem. Phys. 136, 084108 (2012); http://dx.doi.org/10.1063/1.3687341 (10 pages)

Online Publication Date: 29 February 2012

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We report a linear-scaling computation method for evaluating the dynamic first hyperpolarizability β based on the divide-and-conquer (DC) method. In the present scheme, we utilized the quasi-density-matrix expression derived from Wigner's (2n + 1) rule for β, where the quasi-density matrices are constructed from the solution obtained via the DC time-dependent self-consistent field (TD-SCF) method [T. Touma, M. Kobayashi, and H. Nakai, Chem. Phys. Lett. 485, 247 (2010)10.1016/j.cplett.2009.12.043]. Numerical evaluation of π-conjugated and saturated organic chain systems verified that the present scheme considerably reduces the computational time for the β evaluation with a slight loss of accuracy, even around the singular frequency appearing at the electronic excitation energy. This evaluation indicates that the present linear-scaling TD-SCF scheme can also be used to estimate the molecular excitation energy. Furthermore, we succeeded in accurately evaluating the macroscopic second-harmonic generation coefficient of the polyvinylidene fluoride from the molecular (hyper)polarizabilities.
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31.15.xr Self-consistent-field methods
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
42.65.Ky Frequency conversion; harmonic generation, including higher-order harmonic generation

Natural polarizability and flexibility via explicit valency: The case of water

Seyit Kale and Judith Herzfeld

J. Chem. Phys. 136, 084109 (2012); http://dx.doi.org/10.1063/1.3688228 (8 pages)

Online Publication Date: 29 February 2012

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As the dominant physiological solvent, water drives the folding of biological macromolecules, influences conformational changes, determines the ionization states of surface groups, actively participates in catalytic events, and provides “wires” for long-range proton transfer. Elucidation of all these roles calls for atomistic simulations. However, currently available methods do not lend themselves to efficient simulation of proton transfer events, or even polarizability and flexibility. Here, we report that an explicit account of valency can provide a unified description for the polarizability, flexibility, and dissociability of water in one intuitive and efficient setting. We call this approach LEWIS, after the chemical theory that inspires the use of valence electron pairs. In this paper, we provide details of the method, the choice of the training set, and predictions for the neat ambient liquid, with emphasis on structure, dynamics, and polarization. LEWIS water provides a good description of bulk properties, and dipolar and quadrupolar responses.
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87.15.rs Dissociation
33.15.Fm Bond strengths, dissociation energies
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
33.15.Mt Rotation, vibration, and vibration-rotation constants

Stochastic self-assembly of incommensurate clusters

M. R. D’Orsogna, G. Lakatos, and T. Chou

J. Chem. Phys. 136, 084110 (2012); http://dx.doi.org/10.1063/1.3688231 (10 pages)

Online Publication Date: 29 February 2012

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Nucleation and molecular aggregation are important processes in numerous physical and biological systems. In many applications, these processes often take place in confined spaces, involving a finite number of particles. Analogous to treatments of stochastic chemical reactions, we examine the classic problem of homogeneous nucleation and self-assembly by deriving and analyzing a fully discrete stochastic master equation. We enumerate the highest probability steady states, and derive exact analytical formulae for quenched and equilibrium mean cluster size distributions. Upon comparison with results obtained from the associated mass-action Becker-Döring equations, we find striking differences between the two corresponding equilibrium mean cluster concentrations. These differences depend primarily on the divisibility of the total available mass by the maximum allowed cluster size, and the remainder. When such mass “incommensurability” arises, a single remainder particle can “emulsify” the system by significantly broadening the equilibrium mean cluster size distribution. This discreteness-induced broadening effect is periodic in the total mass of the system but arises even when the system size is asymptotically large, provided the ratio of the total mass to the maximum cluster size is finite. Ironically, classic mass-action equations are fairly accurate in the coarsening regime, before equilibrium is reached, despite the presence of large stochastic fluctuations found via kinetic Monte-Carlo simulations. Our findings define a new scaling regime in which results from classic mass-action theories are qualitatively inaccurate, even in the limit of large total system size.
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82.20.Uv Stochastic theories of rate constants
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
02.50.Ey Stochastic processes
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Electromagnetically induced transparency with quantum interferometry

Anindita Bhattacharjee and Krishna Rai Dastidar

J. Chem. Phys. 136, 084301 (2012); http://dx.doi.org/10.1063/1.3685419 (6 pages)

Online Publication Date: 23 February 2012

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We have shown that electromagnetically induced transparency can be achieved by control-probe interferometry using two delayed phase-locked ultrashort pulses. Two vibrational wavepackets on the excited state, excited by two delayed phase-locked ultrashort pulses, interfere constructively or destructively leading to enhancement or suppression of absorption to a selective set of vibrational levels. Depending on the phase difference and the delay between the pulses with same carrier frequency, one can design different transparency windows between absorption peaks at consecutive even(odd) vibrational levels by eliminating absorption at odd(even) vibrational levels. We have shown that by switching the phase difference of two delayed femtosecond pulses, one can switch to complete elimination of absorption from enhanced absorption to a particular set of vibrational levels in the excited state. Thus, switching of transparency through window between odd vibrational levels to that between even vibrational levels is possible. By properly choosing the temporal width and the carrier frequency of the pulses, lossless transmission of complete or bands of frequencies of the pulses can be achieved through these transparency windows. Hence, designing of single- or multi-mode transparency windows in NaH molecule is feasible by control-probe quantum interferometry.
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42.50.Md Optical transient phenomena: quantum beats, photon echo, free-induction decay, dephasings and revivals, optical nutation, and self-induced transparency
42.50.-p Quantum optics
07.60.Ly Interferometers
42.60.Fc Modulation, tuning, and mode locking
42.15.Eq Optical system design
42.65.Re Ultrafast processes; optical pulse generation and pulse compression

In search of the next Holy Grail of polyoxide chemistry: Explicitly correlated ab initio full quartic force fields for HOOH, HOOOH, HOOOOH, and their isotopologues

David S. Hollman and Henry F. Schaefer, III

J. Chem. Phys. 136, 084302 (2012); http://dx.doi.org/10.1063/1.3684231 (9 pages)

Online Publication Date: 24 February 2012

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Explicitly correlated ab initio methods have been used to compute full quartic force fields for the three chain minima for HOOOOH, which are found to lie within 1 kcal mol−1. The CCSD(T)-F12 method with the cc-pVTZ-F12 basis set was used to compute equilibrium structures, anharmonic vibrational frequencies, and rotational constants for HOOH, HOOOH, and three chain isomers of HOOOOH, with the two former force fields being used as benchmarks for the latter three. The full quartic force fields were computed in such a way as to yield fundamental frequencies for all isotopologues at once. The present research confirms the recent experimental identification of HOOOH and provides reliable force fields in support of future experimental work on the enigmatic bonding paradigms involved in the HOOOOH chain.
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82.20.Tr Kinetic isotope effects including muonium
82.30.Qt Isomerization and rearrangement
31.15.bw Coupled-cluster theory
33.20.Tp Vibrational analysis
33.15.Fm Bond strengths, dissociation energies

Collisional electron transfer to photoexcited acceptor radical anions

Jean Ann Wyer, Kristian Støchkel, and Steen Brøndsted Nielsen

J. Chem. Phys. 136, 084303 (2012); http://dx.doi.org/10.1063/1.3682245 (5 pages)

Online Publication Date: 24 February 2012

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In this article, we show that photoexcitation of radical anions facilitates electron transfer from sodium atoms in femtosecond encounters. Thus, excitation of 7,7,8,8-tetracyano-p-quinodimethane (TCNQ) and fluorinated TCNQ (TCNQ-F4) anions to the second optically active state at 478 nm led to increases in the yields of dianions of about 20% and 10%, respectively. Photoexcitation with a nanosecond-long laser pulse was done a few microseconds before the ions entered the sodium collision cell so that none of the ions would be in any of the initially reached doublet-excited states. We suggest an explanation for the higher electron capture cross section based on the formation of long-lived quartet state anions. Excitation of TCNQ anions within the lowest-energy absorption band, where there are no accessible quartet states, led instead to a lower yield of dianions. There are at least three explanations for the lower dianion yields: (1) Depletion of the monoanion beam due to photodetachment after the absorption of minimum two photons; (2) Formation of short-lived vibrationally excited dianions that decay by electron autodetachment prior to identification; and (3) Lower electron capture cross sections of vibrationally excited monoanions. Similar losses in dianion signal can occur at 478 nm so the actual yield of dianions at this wavelength due to the population of quartet states is therefore greater than that observed. Our methodology devises a more efficient route for the production of molecular dianions, and at the same time it may provide information on long-lived electronic states.
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33.80.Eh Autoionization, photoionization, and photodetachment
33.15.Mt Rotation, vibration, and vibration-rotation constants
34.70.+e Charge transfer
33.20.Kf Visible spectra
33.20.Ea Infrared spectra

Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). I. A theoretical study

E. Kamarchik, C. Rodrigo, J. M. Bowman, H. Reisler, and A. I. Krylov

J. Chem. Phys. 136, 084304 (2012); http://dx.doi.org/10.1063/1.3685891 (8 pages)

Online Publication Date: 24 February 2012

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The dissociation of the hydroxymethyl radical, CH2OH, and its isotopolog, CD2OH, following the excitation of high OH stretch overtones is studied by quasi-classical molecular dynamics calculations using a global potential energy surface (PES) fitted to ab initio calculations. The PES includes CH2OH and CH3O minima, dissociation products, and all relevant barriers. Its analysis shows that the transition states for OH bond fission and isomerization are both very close in energy to the excited vibrational levels reached in recent experiments and involve significant geometry changes relative to the CH2OH equilibrium structure. The energies of key stationary points are refined using high-level electronic structure calculations. Vibrational energies and wavefunctions are computed by coupled anharmonic vibrational calculations. They show that high OH-stretch overtones are mixed with other modes. Consequently, trajectory calculations carried out at energies about ∼3000 cm−1 above the barriers reveal that despite initial excitation of the OH stretch, the direct OH bond fission is relatively slow (10 ps) and a considerable fraction of the radicals undergoes isomerization to the methoxy radical. The computed dissociation energies are: D0(CH2OH → CH2O + H) = 10 188 cm−1, D0(CD2OH → CD2O + H) = 10 167 cm−1, D0(CD2OH → CHDO + D) = 10 787 cm−1. All are in excellent agreement with the experimental results. For CH2OH, the barriers for the direct OH bond fission and isomerization are: 14 205 and 13 839 cm−1, respectively.
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82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
82.30.Qt Isomerization and rearrangement
82.20.Kh Potential energy surfaces for chemical reactions
71.15.Pd Molecular dynamics calculations (Car-Parrinello) and other numerical simulations
63.50.-x Vibrational states in disordered systems

Overtone-induced dissociation and isomerization dynamics of the hydroxymethyl radical (CH2OH and CD2OH). II. Velocity map imaging studies

M. Ryazanov, C. Rodrigo, and H. Reisler

J. Chem. Phys. 136, 084305 (2012); http://dx.doi.org/10.1063/1.3685899 (9 pages)

Online Publication Date: 24 February 2012

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The dissociation of the hydroxymethyl radical, CH2OH, and its isotopolog, CD2OH, following excitation in the 4ν1 region (OH stretch overtone, near 13 600 cm−1) was studied using sliced velocity map imaging. A new vibrational band near 13 660 cm−1 arising from interaction with the antisymmetric CH stretch was discovered for CH2OH. In CD2OH dissociation, D atom products (correlated with CHDO) were detected, providing the first experimental evidence of isomerization in the CH2OH ↔ CH3O (CD2OH ↔ CHD2O) system. Analysis of the H (D) fragment kinetic energy distributions shows that the rovibrational state distributions in the formaldehyde cofragments are different for the OH bond fission and isomerization pathways. Isomerization is responsible for 10%–30% of dissociation events in all studied cases, and its contribution depends on the excited vibrational level of the radical. Accurate dissociation energies were determined: D0(CH2OH → CH2O + H) = 10 160 ± 70 cm−1, D0(CD2OH → CD2O + H) = 10 135 ± 70 cm−1, D0(CD2OH → CHDO + D) = 10 760 ± 60 cm−1.
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82.30.Cf Atom and radical reactions; chain reactions; molecule-molecule reactions
33.15.Mt Rotation, vibration, and vibration-rotation constants
82.30.Qt Isomerization and rearrangement
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)
33.15.Fm Bond strengths, dissociation energies

Surface temperature effect on the scattering of D2(v = 0, j = 0)-Cu(111) system

Tapas Sahoo, Saikat Mukherjee, and Satrajit Adhikari

J. Chem. Phys. 136, 084306 (2012); http://dx.doi.org/10.1063/1.3687175 (9 pages)

Online Publication Date: 24 February 2012

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We perform four-dimensional (4D⊗2D) as well as six-dimensional (6D) quantum dynamics on a parametrically time- and temperature-dependent effective Hamiltonian for D2(v, j)-Cu(111) system, where such effective potential has been derived through a mean-field approach between molecular degrees of freedom and surface modes with Bose-Einstein probability factor for their initial state distribution. We present the convergence of the theoretically calculated sticking probabilities employing 4D⊗2D quantum dynamics with increasing number of surface atoms as well as layers for rigid surface and the surface at a particular temperature, where the temperature-dependent sticking probabilities appear exclusively dictated by those surface modes directed along the Z-axis. The sticking and state-to-state transition probabilities obtained from 6D quantum dynamics are shown as a function of initial kinetic energy of the diatom at different surface temperature. Theoretically calculated sticking probabilities display the similar trend with the experimentally measured one.
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34.35.+a Interactions of atoms and molecules with surfaces
33.70.Ca Oscillator and band strengths, lifetimes, transition moments, and Franck-Condon factors
68.43.Mn Adsorption kinetics

Low-energy electron collisions with glycine

Josué S. dos Santos, Romarly F. da Costa, and Márcio T. do N. Varella

J. Chem. Phys. 136, 084307 (2012); http://dx.doi.org/10.1063/1.3687345 (7 pages)

Online Publication Date: 27 February 2012

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We report cross sections for elastic electron scattering by gas phase glycine (neutral form), obtained with the Schwinger multichannel method. The present results are the first obtained with a new implementation that combines parallelization with OpenMP directives and pseudopotentials. The position of the well known π* shape resonance ranged from 2.3 eV to 2.8 eV depending on the polarization model and conformer. For the most stable isomer, the present result (2.4 eV) is in fair agreement with electron transmission spectroscopy assignments (1.93 ± 0.05 eV) and available calculations. Our results also point out a shape resonance around 9.5 eV in the A′ symmetry that would be weakly coupled to vibrations of the hydroxyl group. Since electron attachment to a broad and lower lying σ* orbital located on the OH bond has been suggested the underlying mechanism leading to dissociative electron attachment at low energies, we sought for a shape resonance around ∼4 eV. Though we obtained cross sections with the target molecule at the equilibrium geometry and with stretched OH bond lengths, least-squares fits to the calculated eigenphase sums did not point out signatures of this anion state (though, in principle, it could be hidden in the large background). The low energy (∼1 eV) integral cross section strongly scales as the bond length is stretched, and this could indicate a virtual state pole, since dipole supported bound states are not expected at the geometries addressed here.
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87.15.B- Structure of biomolecules
87.15.mk Photodissociation
87.64.ks Electron and photoelectron
33.15.Dj Interatomic distances and angles
34.80.Ht Dissociation and dissociative attachment
87.14.E- Proteins

Ab initio study of dynamical E × e Jahn-Teller and spin-orbit coupling effects in the transition-metal trifluorides TiF3, CrF3, and NiF3

Padmabati Mondal, Daniel Opalka, Leonid V. Poluyanov, and Wolfgang Domcke

J. Chem. Phys. 136, 084308 (2012); http://dx.doi.org/10.1063/1.3687001 (12 pages)

Online Publication Date: 27 February 2012

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Multiconfiguration ab initio methods have been employed to study the effects of Jahn-Teller (JT) and spin-orbit (SO) coupling in the transition-metal trifluorides TiF3, CrF3, and NiF3, which possess spatially doubly degenerate excited states (ME) of even spin multiplicities (M = 2 or 4). The ground states of TiF3, CrF3, and NiF3 are nondegenerate and exhibit minima of D3h symmetry. Potential-energy surfaces of spatially degenerate excited states have been calculated using the state-averaged complete-active-space self-consistent-field method. SO coupling is described by the matrix elements of the Breit-Pauli operator. Linear and higher order JT coupling constants for the JT-active bending and stretching modes as well as SO-coupling constants have been determined. Vibronic spectra of JT-active excited electronic states have been calculated, using JT Hamiltonians for trigonal systems with inclusion of SO coupling. The effect of higher order (up to sixth order) JT couplings on the vibronic spectra has been investigated for selected electronic states and vibrational modes with particularly strong JT couplings. While the weak SO couplings in TiF3 and CrF3 are almost completely quenched by the strong JT couplings, the stronger SO coupling in NiF3 is only partially quenched by JT coupling.
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31.15.A- Ab initio calculations
31.50.Df Potential energy surfaces for excited electronic states
33.20.Wr Vibronic, rovibronic, and rotation-electron-spin interactions
31.15.xr Self-consistent-field methods

Nuclear spin selective laser control of rotational and torsional dynamics

J. Floß, T. Grohmann, M. Leibscher, and T. Seideman

J. Chem. Phys. 136, 084309 (2012); http://dx.doi.org/10.1063/1.3687343 (11 pages)

Online Publication Date: 28 February 2012

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We explore the possibility of controlling rotational-torsional dynamics of non-rigid molecules with strong, non-resonant laser pulses and demonstrate that transient, laser-induced torsional alignment depends on the nuclear spin of the molecule. Consequently, nuclear spin isomers can be manipulated selectively by a sequence of time-delayed laser pulses. We show that two pulses with different polarization directions can induce either overall rotation or internal torsion, depending on the nuclear spin. Nuclear spin selective control of the angular momentum distribution may open new ways to separate and explore nuclear spin isomers of polyatomic molecules.
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33.80.-b Photon interactions with molecules
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)
33.15.Mt Rotation, vibration, and vibration-rotation constants

A new ab initio intermolecular potential energy surface and predicted rotational spectra of the Ar−H2S complex

Jinping Lei, Yanzi Zhou, and Daiqian Xie

J. Chem. Phys. 136, 084310 (2012); http://dx.doi.org/10.1063/1.3689443 (7 pages)

Online Publication Date: 28 February 2012

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We report a reliable three-dimensional ab initio intermolecular potential energy surface for the Ar−H2S complex with H2S monomer fixed at its experimental average structure. The potential energies were evaluated using the supermolecular approach at the coupled-cluster level with a large basis set including bond functions. The full counterpoise procedure was used to correct the basis set superposition error. The potential has a planar T-shaped global minimum with a well depth of 177.48 cm−1 at the intermolecular distance of 3.72 Å. An additional planar local minimum is also found and is separated from the global minimum with an energy barrier with a height of 47.46 cm−1. The combined radial discrete variable representation/angular finite basis representation method and the Lanczos algorithm were employed to calculate the rovibrational energy levels for three isotopic species of Ar−H2S complexes (Ar−H232S, Ar−H233S, and Ar−H234S). The rotational transition frequencies and structural parameters for the three isotopomers were also determined for the ground and the first excited states, which are all in good agreement with the available experimental values.
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31.15.ae Electronic structure and bonding characteristics
31.15.bw Coupled-cluster theory
31.30.Gs Hyperfine interactions and isotope effects
31.50.Bc Potential energy surfaces for ground electronic states
31.50.Df Potential energy surfaces for excited electronic states
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)

Ab initio properties of MgAlk (Alk = Li, Na, K, Rb, Cs)

L. Augustovičová and P. Soldán

J. Chem. Phys. 136, 084311 (2012); http://dx.doi.org/10.1063/1.3690459 (4 pages)

Online Publication Date: 29 February 2012

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High level ab initio calculations are performed on the ground electronic state of diatomic molecules MgAlk (Alk = Li, Na, K, Rb, Cs). Potential energy curves and dipole moment functions are determined making use of the single-reference unrestricted and restricted coupled-cluster methods with large basis sets. Basic spectroscopic properties of the ground electronic states are derived from ro-vibrational bound state calculations.
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31.15.bw Coupled-cluster theory
31.50.Bc Potential energy surfaces for ground electronic states
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
33.20.Vq Vibration-rotation analysis
back to top Condensed Phase Dynamics, Structure, and Thermodynamics: Spectroscopy, Reactions, and Relaxation

A set of molecular models for alkali and halide ions in aqueous solution

Stephan Deublein, Jadran Vrabec, and Hans Hasse

J. Chem. Phys. 136, 084501 (2012); http://dx.doi.org/10.1063/1.3687238 (10 pages)

Online Publication Date: 22 February 2012

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This work presents new molecular models for alkali and halide ions in aqueous solution. The force fields were parameterized with respect to the reduced liquid solution density at 293.15 K and 1 bar, considering all possible ion combinations simultaneously. The experimental target data are reproduced with a high accuracy over a wide range of salinity. The ion models predict structural properties of electrolyte solutions well, such as pair correlation functions and hydration numbers. The force fields provide good predictions of the properties studied here in combination with different models for water.
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61.20.Ne Structure of simple liquids
61.20.Gy Theory and models of liquid structure
82.30.Nr Association, addition, insertion, cluster formation

The effect of the spatial nonlocality of the Kirkwood g-factor on the determination of the long wavelength dielectric functions in dipolar fluids

Robert L. Fulton

J. Chem. Phys. 136, 084502 (2012); http://dx.doi.org/10.1063/1.3687239 (9 pages)

Online Publication Date: 23 February 2012

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The Kirkwood g-factor that determines the long wavelength dielectric constant of a simple, isotropic, translationally invariant dipolar fluid is given by an integral of a dipole-dipole correlation function over a spherical region of a nonzero radius RK chosen such that any further increase in the radius leads to no change in the value of the integral, thereby defining a Kirkwood correlation length RK. For radii less than the correlation length the integral defines a radius dependent (nonlocal) Kirkwood g-factor, implying a nonlocal dielectric function. The nonlocal nature of these quantities has important consequences for the determination of the long wavelength dielectric function from dipole fluctuations via the Kirkwood-Fröhlich connection. The dipole-dipole correlation function (the volume dipole auto-correlation function) commonly used in this determination involves particles residing solely within a sphere of radius R, unlike the correct correlation function which involves either a single particle with those particles in a spherical volume of radius RK or those particles in a spherical volume of radius R with those residing within a spherical volume of radius R+RK. A procedure is suggested for extracting the infinite system dipole-dipole correlation function from results of simulations performed on finite spherical samples. Using some results reported in the recent literature, relative to the accurate correlation function the commonly used correlation function ranges from 27% too small for a sphere having a radius comparable to the Kirkwood correlation length to 4% too small at a radius of seven times that correlation length. As a result, the apparent dielectric constants, as determined by the conventional procedure of using the fluctuations of the sum of dipoles in a finite fixed volume, are also too small. This suggests that a dielectric constant extracted from computer simulations using a total dipole-total dipole correlation function in a given volume with other geometries and/or boundary conditions will result in similar errors.
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77.22.Ch Permittivity (dielectric function)
05.40.-a Fluctuation phenomena, random processes, noise, and Brownian motion
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