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22 Dec 2004

Volume 121, Issue 24, pp. 12135-12773

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Solvation states of HCl in mixed ether:acid crystals: A computational study

V. Buch, F. Mohamed, Mathias Krack, J. Sadlej, J. P. Devlin, and M. Parrinello

J. Chem. Phys. 121, 12135 (2004); http://dx.doi.org/10.1063/1.1839051 (4 pages) | Cited 6 times

Online Publication Date: 13 December 2004

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Acid solvation states are investigated in the recently discovered mixed ether:acid crystalline solids. The solids are simulated using on-the-fly molecular dynamics as implemented in the density functional code QUICKSTEP employing Gaussian basis sets. The solids are shown to display a remarkably broad range of acid solvation states, depending on the ether:acid ratio, including proton sharing in the 1:1 case, proton transfer to the ether in 1:2, and perturbed molecular acid in 1:6. The observed variation of the infrared spectra with the composition is accounted for qualitatively with the help of the calculations. © 2004 American Institute of Physics.
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82.30.Nr Association, addition, insertion, cluster formation
61.66.Hq Organic compounds
82.30.Hk Chemical exchanges (substitution, atom transfer, abstraction, disproportionation, and group exchange)
78.30.Jw Organic compounds, polymers

Energy controlled insertion of polar molecules in dense fluids

Gianni De Fabritiis, Rafael Delgado-Buscalioni, and Peter V. Coveney

J. Chem. Phys. 121, 12139 (2004); http://dx.doi.org/10.1063/1.1835957 (4 pages) | Cited 14 times

Online Publication Date: 13 December 2004

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We present a method to search low energy configurations of polar molecules in the complex potential energy surfaces associated with dense fluids. The search is done in the configurational space of the translational and rotational degrees of freedom of the molecule, combining steepest-descent and Newton–Raphson steps which embed information on the average sizes of the potential energy wells obtained from prior inspection of the liquid structure. We perform a molecular dynamics simulation of a liquid water shell which demonstrates that the method enables fast and energy-controlled water molecule insertion in aqueous environments. The algorithm finds low energy configurations of incoming water molecules around three orders of magnitude faster than direct random insertion. This method represents an important step towards dynamic simulations of open systems and it may also prove useful for energy-biased ensemble average calculations of the chemical potential.© 2004 American Institute of Physics.
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61.20.Ja Computer simulation of liquid structure
02.60.-x Numerical approximation and analysis

Vibrational relaxation of the H2O bending mode in liquid water

Olaf F. A. Larsen and Sander Woutersen

J. Chem. Phys. 121, 12143 (2004); http://dx.doi.org/10.1063/1.1839175 (3 pages) | Cited 21 times

Online Publication Date: 13 December 2004

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We have studied the vibrational relaxation of the H2O bending mode in an H2O:HDO:D2O isotopic mixture using infrared pump–probe spectroscopy. The transient spectrum and its delay dependence reveal an anharmonic shift of 55±10 cm−1 for the H2O bending mode, and a value of 400±30 fs for its vibrational lifetime.© 2004 American Institute of Physics.
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78.30.C- Liquids
34.50.Ez Rotational and vibrational energy transfer
33.70.Jg Line and band widths, shapes, and shifts
31.30.Gs Hyperfine interactions and isotope effects
64.75.-g Phase equilibria
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back to top Theoretical Methods and Algorithms

Convergence of triples energy in CCSD(T) and CC3 calculations with correlation-consistent basis sets

Eduardo Fischli Laschuk and Paolo Roberto Livotto

J. Chem. Phys. 121, 12146 (2004); http://dx.doi.org/10.1063/1.1821495 (5 pages) | Cited 5 times

Online Publication Date: 13 December 2004

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The convergence behavior of connected triples correlation energy in CCSD(T) and CC3 calculations with (aug-)cc-pVXZ basis sets has been accurately described in terms of a power law of the type EX = E∞+AX−4. Calculations ranging from double-Z through septuple-Z attest the validity of this X−4 convergence model. Extrapolations generated from (X−1,X)-Z calculations yield energies of nearly (X+1)-Z quality. Typically, the fraction of triples correlation energy recovered is 0.92±0.05 in (D,T) extrapolations; 0.98±0.01 in (T,Q) extrapolations; 1.0002±0.0012 in (Q,5) extrapolations; and 0.9995±0.0005 in (5,6) extrapolations. © 2004 American Institute of Physics.
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31.15.bw Coupled-cluster theory
31.15.vj Electron correlation calculations for atoms and ions: excited states

Exchange-correlation potentials for high-electron-density ions in the Be isoelectronic series

Robert C. Morrison and Libero J. Bartolotti

J. Chem. Phys. 121, 12151 (2004); http://dx.doi.org/10.1063/1.1824877 (7 pages) | Cited 1 time

Online Publication Date: 13 December 2004

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Accurate reference wave functions and their densities have been used to obtain accurate exchange-correlation potentials for the beryllium isoelectronic sequence Be, Ne+6, Ar+14, and Kr+32. The exchange-correlation potentials for the four-electron cations with high Z in this sequence exhibit structure prior to the intershell peak that is not present in neutral atoms. The kinetic energy contribution to the exchange-correlation potential contributes to the early structure as well as to the intershell peak. The near degeneracy in this four-electron sequence plays a significant role in the structure prior to the intershell peak. Several of the quantities on which the Perdew–Burke–Ernzerhoff and Tao–Perdew–Staroverov–Scuseria functionals are dependent are examined. The generalized gradient approximations appear not to account for the near degeneracy in this series. © 2004 American Institute of Physics.
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31.15.E- Density-functional theory
31.15.ve Electron correlation calculations for atoms and ions: ground state
02.60.Ed Interpolation; curve fitting

Vibrational molecular quantum computing: Basis set independence and theoretical realization of the Deutsch–Jozsa algorithm

Carmen M. Tesch and Regina de Vivie-Riedle

J. Chem. Phys. 121, 12158 (2004); http://dx.doi.org/10.1063/1.1818131 (11 pages) | Cited 62 times

Online Publication Date: 13 December 2004

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The phase of quantum gates is one key issue for the implementation of quantum algorithms. In this paper we first investigate the phase evolution of global molecular quantum gates, which are realized by optimally shaped femtosecond laser pulses. The specific laser fields are calculated using the multitarget optimal control algorithm, our modification of the optimal control theory relevant for application in quantum computing. As qubit system we use vibrational modes of polyatomic molecules, here the two IR-active modes of acetylene. Exemplarily, we present our results for a Π gate, which shows a strong dependence on the phase, leading to a significant decrease in quantum yield. To correct for this unwanted behavior we include pressure on the quantum phase in our multitarget approach. In addition the accuracy of these phase corrected global quantum gates is enhanced. Furthermore we could show that in our molecular approach phase corrected quantum gates and basis set independence are directly linked. Basis set independence is also another property highly required for the performance of quantum algorithms. By realizing the Deutsch–Jozsa algorithm in our two qubit molecular model system, we demonstrate the good performance of our phase corrected and basis set independent quantum gates. © 2004 American Institute of Physics.
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03.67.Lx Quantum computation architectures and implementations
02.30.Yy Control theory
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Tp Vibrational analysis
03.65.-w Quantum mechanics

The numerical stability of leaping methods for stochastic simulation of chemically reacting systems

Yang Cao, Linda R. Petzold, Muruhan Rathinam, and Daniel T. Gillespie

J. Chem. Phys. 121, 12169 (2004); http://dx.doi.org/10.1063/1.1823412 (10 pages) | Cited 23 times

Online Publication Date: 13 December 2004

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Tau-leaping methods have recently been proposed for the acceleration of discrete stochastic simulation of chemically reacting systems. This paper considers the numerical stability of these methods. The concept of stochastic absolute stability is defined, discussed, and applied to the following leaping methods: the explicit tau, implicit tau, and trapezoidal tau.© 2004 American Institute of Physics.
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82.20.Uv Stochastic theories of rate constants
82.20.Wt Computational modeling; simulation
87.15.R- Reactions and kinetics
82.30.Qt Isomerization and rearrangement
02.60.Cb Numerical simulation; solution of equations

A study of the adiabatic connection for two-electron systems

Jacob Katriel, Sudip Roy, and Michael Springborg

J. Chem. Phys. 121, 12179 (2004); http://dx.doi.org/10.1063/1.1824879 (12 pages) | Cited 7 times

Online Publication Date: 13 December 2004

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Some aspects of the adiabatic connection method are studied for two-particle spherically symmetric systems. Ground-state wave functions that are constrained by means of a set of moments to have the same density as a corresponding fully interacting system are obtained for noninteracting or partially interacting systems. Local one-body potentials that support these constrained wave functions are generated using a simple method. We examine an interacting two-particle system with a parameter-dependent one-body potential, which for a particular value of that parameter exhibits an intersection between the 3S and the 3P states, whereas the 2s and 2p eigenvalues of the corresponding Kohn–Sham potentials do not intersect along with the total energies. These results show that there do exist cases where occupying the orbitals from below in energy may not lead to the ground state, and that the inherent assumptions behind the adiabatic connection can sometimes be violated.© 2004 American Institute of Physics.
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31.15.E- Density-functional theory

Time-dependent density functional theory based on a noncollinear formulation of the exchange-correlation potential

Fan Wang and Tom Ziegler

J. Chem. Phys. 121, 12191 (2004); http://dx.doi.org/10.1063/1.1821494 (6 pages) | Cited 71 times

Online Publication Date: 13 December 2004

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In this study we have introduced a formulation of time-dependent density functional theory (TDDFT) based on a noncollinear exchange-correlation potential. This formulation is a generalization of conventional TDDFT. The form of this formulation is exactly the same as that of the conventional TDDFT for the excitation energies of transitions that do not involve spin flips. In addition, this noncollinear TDDFT formulation allows for spin-flip transitions. This feature makes it possible to resolve more fully excited state spin multiplets, while for closed-shell systems, the spin-flip transitions will result in singlet-triplet excitations and this excitation energy calculated from this formulation of TDDFT is exactly the same as that from ordinary TDDFT. This formulation is applied to the dissociation of H2 in its 1Σg+ ground state and 1Σu+ and 3Σu− excited states with 3Σu− (Ms = +1) as the reference state and the multiplets splitting of some atoms.© 2004 American Institute of Physics.
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31.15.E- Density-functional theory
31.50.Df Potential energy surfaces for excited electronic states
82.37.Np Single molecule reaction kinetics, dissociation, etc.

Combined coupled-cluster and many-body perturbation theories

So Hirata, Peng-Dong Fan, Alexander A. Auer, Marcel Nooijen, and Piotr Piecuch

J. Chem. Phys. 121, 12197 (2004); http://dx.doi.org/10.1063/1.1814932 (11 pages) | Cited 66 times

Online Publication Date: 13 December 2004

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Various approximations combining coupled-cluster (CC) and many-body perturbation theories have been derived and implemented into the parallel execution programs that take into account the spin, spatial (real Abelian), and permutation symmetries and that are applicable to closed- and open-shell molecules. The implemented models range from the CCSD(T), CCSD[T], CCSD(2)T, CCSD(2)TQ, and CCSDT(2)Q methods to the completely renormalized (CR) CCSD(T) and CCSD[T] approaches, where CCSD (CCSDT) stands for the CC method with connected single and double (single, double, and triple) cluster operators, and subscripted or parenthesized 2, T, and Q indicate the perturbation order or the excitation ranks of the cluster operators included in the corrections. The derivation and computer implementation have been automated by the algebraic and symbolic manipulation program TENSOR CONTRACTION ENGINE (TCE). The TCE-synthesized subroutines generate the tensors with the highest excitation rank in a blockwise manner so that they need not be stored in their entirety, while enabling the efficient reuse of other precalculated intermediate tensors defined by prioritizing the memory optimization as well as operation minimization. Consequently, the overall storage requirements for the corrections due to connected triple and quadruple cluster operators scale as O(n4) and O(n6), respectively (n being a measure of the system size). For systems with modest multireference character of their wave functions, we found that the order of accuracy is CCSD<CR-CCSD(T) ≈ CCSD(2)T ≈ CCSD(T)<CCSDT ≈ CCSD(2)TQ<CCSDT(2)Q, whereas CR-CCSD(T) is more effective in cases of larger quasidegeneracy. The operation costs of the TCE-generated CCSD(2)TQ and CCSDT(2)Q codes scale as rather steep O(n9), while the TCE-generated CCSD(T), CCSD(2)T, and CR-CCSD(T) codes are near operation minimum [a noniterative O(n7)]. The perturbative correction part of the CCSD(T)/cc-pVDZ calculations for azulene exhibited a 45-fold speedup upon a 64-fold increase in the number of processors from 8 to 512.© 2004 American Institute of Physics.
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31.15.bw Coupled-cluster theory
31.15.xp Perturbation theory

Wavepacket propagation using time-sliced semiclassical initial value methods

Brett B. Wallace and Jeffrey R. Reimers

J. Chem. Phys. 121, 12208 (2004); http://dx.doi.org/10.1063/1.1825999 (9 pages) | Cited 1 time

Online Publication Date: 13 December 2004

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A new semiclassical initial value representation (SC-IVR) propagator and a SC-IVR propagator originally introduced by Kay [J. Chem. Phys. 100, 4432 (1994)], are investigated for use in the split-operator method for solving the time-dependent Schrödinger equation. It is shown that the SC-IVR propagators can be derived from a procedure involving modified Filinov filtering of the Van Vleck expression for the semiclassical propagator. The two SC-IVR propagators have been selected for investigation because they avoid the need to perform a coherent state basis set expansion that is necessary in other time-slicing propagation schemes. An efficient scheme for solving the propagators is introduced and can be considered to be a semiclassical form of the effective propagators of Makri [Chem. Phys. Lett. 159, 489 (1989)]. Results from applications to a one-dimensional, two-dimensional, and three-dimensional Hamiltonian for a double-well potential are presented.© 2004 American Institute of Physics.  
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03.65.Sq Semiclassical theories and applications
03.65.Ge Solutions of wave equations: bound states
02.30.-f Function theory, analysis

One-electron versus electron–electron interaction contributions to the spin–spin coupling mechanism in nuclear magnetic resonance spectroscopy: Analysis of basic electronic effects

Jürgen Gräfenstein and Dieter Cremer

J. Chem. Phys. 121, 12217 (2004); http://dx.doi.org/10.1063/1.1825993 (16 pages) | Cited 4 times

Online Publication Date: 13 December 2004

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For the first time, the nuclear magnetic resonance (NMR) spin–spin coupling mechanism is decomposed into one-electron and electron–electron interaction contributions to demonstrate that spin-information transport between different orbitals is not exclusively an electron-exchange phenomenon. This is done using coupled perturbed density-functional theory in conjunction with the recently developed J-OC-PSP [=J-OC-OC-PSP: Decomposition of J into orbital contributions using orbital currents and partial spin polarization)] method. One-orbital contributions comprise Ramsey response and self-exchange effects and the two-orbital contributions describe first-order delocalization and steric exchange. The two-orbital effects can be characterized as external orbital, echo, and spin transport contributions. A relationship of these electronic effects to zeroth-order orbital theory is demonstrated and their sign and magnitude predicted using simple models and graphical representations of first order orbitals. In the case of methane the two NMR spin–spin coupling constants result from totally different Fermi contact coupling mechanisms. 1J(C,H) is the result of the Ramsey response and the self-exchange of the bond orbital diminished by external first-order delocalization external one-orbital effects whereas 2J(H,H) spin–spin coupling is almost exclusively mitigated by a two-orbital steric exchange effect. From this analysis, a series of prediction can be made how geometrical deformations, electron lone pairs, and substituent effects lead to a change in the values of 1J(C,H) and 2J(H,H), respectively, for hydrocarbons. © 2004 American Institute of Physics.
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33.25.+k Nuclear resonance and relaxation
31.15.E- Density-functional theory

Vibrational spectra from atomic fluctuations in dynamics simulations. I. Theory, limitations, and a sample application

Matthias Schmitz and Paul Tavan

J. Chem. Phys. 121, 12233 (2004); http://dx.doi.org/10.1063/1.1822914 (14 pages) | Cited 25 times

Online Publication Date: 13 December 2004

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Hybrid molecular dynamics (MD) simulations, which combine density functional theory (DFT) descriptions of a molecule with a molecular mechanics (MM) modeling of its solvent environment, have opened the way towards accurate computations of solvation effects in the vibrational spectra of molecules. Recently, Wheeler et al. [ChemPhysChem 4, 382 (2002)] have suggested to compute these spectra from DFT/MM-MD trajectories by diagonalizing the covariance matrix of atomic fluctuations. This so-called principal mode analysis (PMA) allegedly can replace the well-established approaches, which are based on Fourier transform methods or on conventional normal mode analyses. By scrutinizing and revising the PMA approach we identify five conditions, which must be guaranteed if PMA is supposed to render exact vibrational frequencies. Besides specific choices of (a) coordinates and (b) coordinate systems, these conditions cover (c) a harmonic intramolecular potential, (d) a complete thermal equilibrium within the molecule, and (e) a molecular Hamiltonian independent of time. However, the PMA conditions [(c)–(d)] and [(c)–(e)] are generally violated in gas phase DFT-MD and liquid phase DFT/MM-MD trajectories, respectively. Based on a series of simple analytical model calculations and on the analysis of MD trajectories calculated for the formaldehyde molecule in the gas phase (DFT) and in liquid water (DFT/MM) we show that in both phases the violation of condition (d) can cause huge errors in PMA frequency computations, whereas the inevitable violations of conditions (c) and (e), the latter being generic to the liquid phase, imply systematic and sizable underestimates of the vibrational frequencies by PMA. We demonstrate that the huge errors, which are caused by an incomplete thermal equilibrium violating (d), can be avoided if one introduces mode-specific temperatures Tj and calculates the frequencies from a “generalized virial” (GV) expression instead from PMA. Concerning ways to additionally remove the remaining errors, which GV still shares with PMA, we refer to Paper II of this work [M. Schmitz and P. Tavan, J. Chem. Phys. 121, 12247 (2004)]. © 2004 American Institute of Physics.
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33.20.Tp Vibrational analysis
31.15.E- Density-functional theory
31.70.Dk Environmental and solvent effects
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)

Vibrational spectra from atomic fluctuations in dynamics simulations. II. Solvent-induced frequency fluctuations at femtosecond time resolution

Matthias Schmitz and Paul Tavan

J. Chem. Phys. 121, 12247 (2004); http://dx.doi.org/10.1063/1.1822915 (12 pages) | Cited 18 times

Online Publication Date: 13 December 2004

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The midinfrared (MIR) spectra of molecules in polar solvents exhibit inhomogeneously broadened bands whose spectral positions are shifted as compared to the gas phase. The shifts are caused by interactions with structured solvation shells and the broadenings by fluctuations of these interactions. The MIR spectra can be calculated from hybrid molecular dynamics (MD) simulations, which treat the solute molecule by density functional theory and the solvent by molecular mechanics by the so-called instantaneous normal mode analysis (INMA) or by Fourier transforming the time correlation function (FTTCF) of the molecular dipole moment. In Paper I of this work [M. Schmitz and P. Tavan, J. Chem. Phys. 121, 12233 (2004)] we explored an alternative method based on generalized virial (GV) frequencies noting, however, that GV systematically underestimates frequencies. As shown by us these artifacts are caused by solvent-induced fluctuations of the (i) equilibrium geometry, (ii) force constants, and (iii) normal mode directions as well as by (iv) diagonal and (v) off-diagonal anharmonicities. Here we now show, by analyzing the time scales of fluctuations and sample MD trajectories of formaldehyde in the gas phase and in water, that all these sources of computational artifacts can be made visible by a Fourier analysis of the normal coordinates. Correspondingly, the error sources (i) and (iii)–(v) can be removed by bandpass filtering, as long as the spectral signatures of the respective effects are well separated from the fundamental band. Furthermore, the artifacts arising from effect (ii) can be strongly diminished by a time-resolved version of the GV approach (TF-GV). The TF-GV method then yields for each mode j a trajectory of the vibrational frequency ωj(t∣τ) at a time resolution τ>τj, which is only limited by the corresponding oscillation time τj = 2π/ωj and, thus, is in the femtosecond range. A correlation analysis of these trajectories clearly separates the librational motions from the conformational dynamics of the solvation shells and yields the inhomogeneously broadened MIR spectra, if the theory of motional narrowing is properly included. The MIR spectrum of formaldehyde in solution obtained by TF-GV agrees very well with the FTTCF result, if one applies the so-called “harmonic approximation” quantum correction factor and a temperature scaling to the FTTCF intensities. Also for INMA an excellent agreement is achieved if one disregards a slight INMA overestimate of linewidths.© 2004 American Institute of Physics.
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33.20.Tp Vibrational analysis
31.15.E- Density-functional theory
31.70.Dk Environmental and solvent effects
33.20.Ea Infrared spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.70.Jg Line and band widths, shapes, and shifts
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
back to top Gas Phase Dynamics and Structure: Spectroscopy, Molecular Interactions, Scattering, and Photochemistry

Homogeneous nucleation rates of 1-pentanol

Kristina Iland, Jan Wedekind, Judith Wölk, Paul E. Wagner, and Reinhard Strey

J. Chem. Phys. 121, 12259 (2004); http://dx.doi.org/10.1063/1.1809115 (6 pages) | Cited 18 times

Online Publication Date: 13 December 2004

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We have measured isothermal homogeneous nucleation rates J for 1-pentanol vapor in two different carrier-gases, argon, and helium, using a two-valve nucleation pulse chamber. The nucleation rates cover a range of 105<J/cm−3 s−1<109 at temperatures between 235<T/K<265. We observed no influence of the carrier gas on location and slope of the nucleation rate isotherms. These measurements are part of an international effort to examine 1-pentanol using various experimental techniques, which was initiated in Prague in 1995. In the present paper nucleation rate data obtained by several groups are compared to each other and to the classical nucleation theory. As expected, the classical theory is not able to quantitatively predict the experimental results. Nevertheless, relating the experimental data to the classical theory provides a suitable way to compare data of widely differing nucleation rates obtained by different experimental techniques. This comparison helps judging mutual support of the data and, at the same time, provides a rather interesting insight into the accuracy of the individual experimental techniques. © 2004 American Institute of Physics.  
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64.60.Q- Nucleation
64.70.F- Liquid-vapor transitions

Structural and electronic properties of TaSin (n = 1–13) clusters: A relativistic density functional investigation

Ping Guo, Zhao-Yu Ren, Fan Wang, Jiang Bian, Ju-Guang Han, and Guang-Hou Wang

J. Chem. Phys. 121, 12265 (2004); http://dx.doi.org/10.1063/1.1809609 (11 pages) | Cited 32 times

Online Publication Date: 13 December 2004

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The TaSin (n = 1–13) clusters with doublet, quartet, and sextet spin configurations have been systematically investigated by a relativistic density functional theory with the generalized gradient approximation available in Amsterdam density functional program. The total bonding energies, equilibrium geometries, Mulliken populations as well as Hirshfeld charges of TaSin (n = 1–13) clusters are calculated and presented. The emphasis on the stabilities and electronic properties is discussed. The most stable structures of the small TaSin (n = 1–6) clusters and the evolutional rule of low-lying geometries of the larger TaSin (n = 7–13) clusters are obtained. Theoretical results indicate that the most stable structure of TaSin (n = 1–6) clusters keeps the similar framework as the most stable structure of Sin+1 clusters except for TaSi3 cluster. The Ta atom in the lowest-energy TaSin (n = 1–13) isomers occupies a gradual sinking site, and the site moves from convex, to flatness, and to concave with the number of Si atom varying from 1 to 13. When n = 12, the Ta atom in TaSi12 cluster completely falls into the center of the Si frame, and a cagelike TaSi12 geometry is formed. Meanwhile, the net Mulliken and Hirsheld populations of the Ta atom in the TaSin (n = 1–13) clusters vary from positive to negative, manifesting that the charges in TaSin (n ≥ 12) clusters transfer from Si atoms to Ta atom. Additionally, the contribution of Si–Si and Si–Ta interactions to the stability of TaSin clusters is briefly discussed. Furthermore, the investigations on atomic averaged binding energies and fragmentation energies show that the TaSin (n = 2,3,5,7,10,11,12) clusters have enhanced stabilities. Compared with pure silicon clusters, a universal narrowing of highest occupied molecular orbital—lowest unoccupied molecular orbital gap in TaSin clusters is found. © 2004 American Institute of Physics.
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31.15.E- Density-functional theory
36.40.Cg Electronic and magnetic properties of clusters
36.40.Qv Stability and fragmentation of clusters
36.40.Mr Spectroscopy and geometrical structure of clusters
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy
33.15.Bh General molecular conformation and symmetry; stereochemistry

Infrared spectrum of the I−–D2 anion complex

D. A. Wild and E. J. Bieske

J. Chem. Phys. 121, 12276 (2004); http://dx.doi.org/10.1063/1.1822920 (6 pages) | Cited 5 times

Online Publication Date: 13 December 2004

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The infrared spectrum of the I−–D2 anion complex is measured in the D2 stretch region by monitoring production of I− photofragments. The rotationally resolved spectrum consists of two overlapping Σ-Σ subbands, redshifted by ≈58 cm−1 from the free D2 fundamental vibrational band. These subbands are associated with absorptions by I−–D2 complexes containing ortho and para forms of D2. The measured rotational constants are consistent with a 3.79 Å separation between I− and the D2 center of mass, contracting by 0.08 Å when the D2 subunit is vibrationally excited. Spectroscopic data are used to generate effective radial potential energy curves describing the interaction of ortho and para D2 with I− from which the dissociation energies of I−–D2(ortho) and I−–D2(para) are estimated as D0 = 236 and 297 cm−1, respectively. © 2004 American Institute of Physics.
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33.20.Ea Infrared spectra
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)
33.15.Mt Rotation, vibration, and vibration-rotation constants
33.20.Sn Rotational analysis
33.70.Jg Line and band widths, shapes, and shifts
33.20.Tp Vibrational analysis
33.80.Gj Diffuse spectra; predissociation, photodissociation

The effects of isotope substitution and nuclear spin modifications on the spectra of complexes of tetracene with hydrogen molecules in ultracold 0.37 K He droplets

A. Lindinger, J. P. Toennies, and A. F. Vilesov

J. Chem. Phys. 121, 12282 (2004); http://dx.doi.org/10.1063/1.1819878 (11 pages) | Cited 4 times

Online Publication Date: 13 December 2004

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The van der Waals complexes consisting of single tetracene chromophore molecules with an attached H2, HD, or a D2 molecule have been assembled inside cold (0.37 K), large ( ≈ 1.5×104 atoms) helium droplets. Their laser-induced fluorescence spectra exhibit typically three well isolated fairly sharp [δν(full width at half maximum) ≈ 0.5 cm−1] bands in the spectral region 22220–22300 cm−1. Their positions differ for each isotopomer and also are different for each of the ortho- and para-spin modifications. The common feature (except for D2) with the largest redshift at about 30 cm−1, found also in other related free complexes, is attributed to a strongly bound site above one of the two central benzene rings. The other major features come in pairs spaced 3 cm−1 apart and are not found in similar gas phase studies. This doublet is assigned to a less tightly bound peripheral site with either slightly different configurations or states of the aduct or possibly the He atoms which are stabilized by the surrounding helium bath. The common feature and one branch of the doublet exhibit a pronounced narrow fine structure with spacings of only 0.1 cm−1, which is nearly the same for all complexes as well as for the bare chromophore, and maybe be due to partially resolved rotational structure of the bands. © 2004 American Institute of Physics.
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31.30.Gs Hyperfine interactions and isotope effects
33.50.Dq Fluorescence and phosphorescence spectra
33.20.Sn Rotational analysis
33.70.Jg Line and band widths, shapes, and shifts
33.15.Pw Fine and hyperfine structure
37.10.Mn Slowing and cooling of molecules
37.10.Pq Trapping of molecules

Gas-phase diatomic trications of Se23+, Te23+, and LaF3+

K. Franzreb, J. Hrušák, M. E. Alikhani, J. Lörinčík, R. C. Sobers, and P. Williams

J. Chem. Phys. 121, 12293 (2004); http://dx.doi.org/10.1063/1.1821496 (10 pages) | Cited 12 times

Online Publication Date: 13 December 2004

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Three gas-phase diatomic trications Se23+, Te23+, and LaF3+ have been produced by Ar+ ion beam sputtering of Se, Te, and LaF3 surfaces, respectively. These exotic molecular ions were detected at noninteger m/z values in a magnetic sector mass spectrometer for ion flight times of ⩾13 μs that correspond to lower limits of their respective lifetimes. Se23+ and Te23+ were unambiguously identified by their characteristic isotopic abundances. Ab initio calculations of the electronic structures of Se23+, Te23+, and LaF3+ show that these molecular trications are metastable with respect to dissociation into fragment ions of Se2++Se+, Te2++Te+, and La2++F+, respectively. Their barrier heights are about 0.49, 0.29, and 0.53 eV, and the equilibrium internuclear distances (bond lengths) are about 0.23, 0.27, and 0.26 nm, respectively. The gas-phase diatomic dications Se22+ and Te22+ were also observed and unambiguously identified. They were found to be long-lived metastable molecules as well, whereas LaF2+ is thermochemically stable. © 2004 American Institute of Physics.
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31.15.A- Ab initio calculations
33.15.Ta Mass spectra
33.15.Dj Interatomic distances and angles
82.30.Lp Decomposition reactions (pyrolysis, dissociation, and fragmentation)

The permanent electric dipole moments of iron monoxide, FeO

T. C. Steimle, Jamie Gengler, and Philip J. Hodges

J. Chem. Phys. 121, 12303 (2004); http://dx.doi.org/10.1063/1.1822923 (5 pages) | Cited 5 times

Online Publication Date: 13 December 2004

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The Q(4) and R(4) branch features of the (0,0)D 5Δ4-X 5Δ4 band system and the Q(3) and R(3) branch features of the (0,0)D 5Δ3-X 5Δ3 band system of iron monoxide FeO have been studied by optical Stark spectroscopy. The Stark splittings in the high resolution laser induced fluorescence spectra were analyzed to produce values for the magnitude of the permanent electric dipole moments ∣μ∣ of 4.50±0.03, 4.29±0.05, 2.53±0.04, and 2.58±0.06 D for the X 5Δ4 (v = 0), X 5Δ3 (v = 0), D 5Δ4 (v = 0), and D 5Δ3 (v = 0) states, respectively. The results are compared to several ab initio predictions and to FeC. The qualitative trends are explained in terms of a molecular orbital correlation picture. © 2004 American Institute of Physics.
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33.57.+c Magneto-optical and electro-optical spectra and effects
33.50.Dq Fluorescence and phosphorescence spectra
33.15.Pw Fine and hyperfine structure
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility

Rotational spectrum, potential energy surface, and bound states of the weakly bound complex He–N2O

XiaoGeng Song, Yunjie Xu, Pierre-Nicholas Roy, and Wolfgang Jäger

J. Chem. Phys. 121, 12308 (2004); http://dx.doi.org/10.1063/1.1819875 (7 pages) | Cited 25 times

Online Publication Date: 13 December 2004

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Pure rotational transitions of the weakly bound complex He–N2O and three minor isotopomers (He–14N15NO, He–15N14NO, and He–15N15NO) were measured in the frequency region from 6 to 20 GHz. Predictions for the microwave transition frequencies were based on the infrared work by Tang and McKellar [J. Chem. Phys. 117, 2586 (2002)]. In the case of 14N containing isotopomers, nuclear quadrupole hyperfine structure of the rotational transitions was observed and analyzed. The resulting spectroscopic parameters were used to determine geometrical and dynamical information about the complex. An ab initio potential energy surface was calculated at the coupled cluster level of theory with single and double excitations and perturbative inclusion of triple excitations. This surface was constructed using the augmented correlation consistent polarized valence triple zeta basis set for all atoms with the inclusion of bond functions for the van der Waals bond. Bound state calculations were done to determine the energies of low-lying rovibrational levels that are supported by the potential energy surface. The resulting transition energies agree with the experimental values to 1% or better.© 2004 American Institute of Physics.
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31.15.A- Ab initio calculations
31.15.bw Coupled-cluster theory
33.20.Bx Radio-frequency and microwave spectra
33.15.Mt Rotation, vibration, and vibration-rotation constants
31.50.-x Potential energy surfaces
33.15.Fm Bond strengths, dissociation energies
31.30.Gs Hyperfine interactions and isotope effects
33.15.Pw Fine and hyperfine structure
33.15.Hp Barrier heights (internal rotation, inversion, rotational isomerism, conformational dynamics)

Lowest-energy structures of (C60)nX (X = Li+,Na+,K+,Cl−) and (C60)nYCl (Y = Li,Na,K) clusters for n ⩽ 13

J. Hernández-Rojas, J. Bretón, J. M. Gomez Llorente, and D. J. Wales

J. Chem. Phys. 121, 12315 (2004); http://dx.doi.org/10.1063/1.1819894 (8 pages) | Cited 6 times

Online Publication Date: 13 December 2004

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Basin-hopping global optimization is used to find likely candidates for the lowest minima on the potential energy surface of (C60)nX (X = Li+,Na+,K+,Cl−) and (C60)nYCl (Y = Li,Na,K) clusters with n ⩽ 13. The energy is evaluated using the Girifalco form for the C60 intermolecular potential along with a polarization potential, which depends on the first few nonvanishing C60 multipole polarizabilities. We find that the ions occupy interstitial sites of a (C60)n cluster, the coordination shell being triangular for Li+, tetrahedral for Na+ and K+, and octahedral for Cl−. When the required coordination site does not exist in the corresponding (C60)n global minimum, the lowest minimum of the doped system may be based on an alternative geometry. This situation is particularly common in the Cl− complexes, where the (C60)n global minima with icosahedral packing change into decahedral or closed-packed forms for the ions. In all the ions we find a significant binding energy for the doped cluster. In the alkali chloride complexes the preferred coordination for the diatomic moiety is octahedral and is basically determined by the Cl− ion. However, the smaller polarization energies in this case mean that a change in structure from the (C60)n global minimum does not necessarily occur if there is no octahedral site.© 2004 American Institute of Physics.
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36.40.Mr Spectroscopy and geometrical structure of clusters
34.20.Gj Intermolecular and atom-molecule potentials and forces
33.15.Bh General molecular conformation and symmetry; stereochemistry
33.15.Kr Electric and magnetic moments (and derivatives), polarizability, and magnetic susceptibility
33.15.Ry Ionization potentials, electron affinities, molecular core binding energy

Simulation of x-ray absorption near edge spectra of electronically excited ruthenium tris-2,2′-bipyridine

Luke Campbell and Shaul Mukamel

J. Chem. Phys. 121, 12323 (2004); http://dx.doi.org/10.1063/1.1814101 (11 pages) | Cited 10 times

Online Publication Date: 13 December 2004

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The L3 edge x-ray absorption near edge spectrum (XANES) of the ground electronic state and the metal to ligand charge transfer state of ruthenium tris-2,2′-bipyridine is calculated. The final valence states and energies in the presence of the photoelectron and core hole, and the corresponding transition intensities are computed using time dependent density functional theory with the Becke three-parameter density functional with the Lee-Yang-Parr correlation functional. Calculations show a valence shift of the primary XANES peak and the appearance of the new XANES transition to the hole created by the optical excitation, in agreement with experiment [M. Saes, C. Bressler, R. Abela, D. Grolimund, S. L. Johnson, P. A. Heimann, and M. Chergui, Phys. Rev. Lett. 90, 047403 (2003)]. © 2004 American Institute of Physics.
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33.20.Rm X-ray spectra
33.60.+q Photoelectron spectra
31.15.E- Density-functional theory
31.15.vj Electron correlation calculations for atoms and ions: excited states

Towards benchmark second-order correlation energies for large atoms: Zn2+ revisited

J. R. Flores, R. Słupski, K. Jankowski, and P. Malinowski

J. Chem. Phys. 121, 12334 (2004); http://dx.doi.org/10.1063/1.1821493 (11 pages) | Cited 5 times

Online Publication Date: 13 December 2004

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To provide very accurate reference results for the second-order Møller–Plesset (MP2) energy and its various components for Zn2+, which plays for 3d-electron systems a similar role as Ne for smaller atoms and molecules, we have performed extensive calculation by two completely different implementations of the MP2 method: the finite element method (FEM) and the variation-perturbation (VP) method. The FEM and VP calculations yield partial wave contributions up to lmax = 45 and 12, respectively. Detailed comparison of all FEM and VP energy components for lmax = 12 has disclosed an extraordinary similarity, which justifies using the present results as benchmarks. The present correlation energies are compared with other works. The dependability of an earlier version of FEM, already applied to very large closed-shell atoms, is confirmed. It has been found that for larger atoms the accuracy of the analytical Hartree–Fock results has an impact on the accuracy of the MP2 energies greater than for smaller atoms. Fields of applications of the present results in studies of various electron correlation effects in 3d-electron atoms and molecules are indicated. © 2004 American Institute of Physics.
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31.15.xp Perturbation theory
31.15.V- Electron correlation calculations for atoms, ions and molecules
31.15.xr Self-consistent-field methods

Infrared spectrum and predissociation dynamics of H2O+–Ar

O. Dopfer and V. Engel

J. Chem. Phys. 121, 12345 (2004); http://dx.doi.org/10.1063/1.1825998 (8 pages) | Cited 2 times

Online Publication Date: 13 December 2004

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The infrared (IR) spectrum and vibrational predissociation of the proton-bound H2O+–Ar ionic complex are investigated within an ab initio and quantum dynamical study. For this purpose, a two-dimensional potential energy surface (2D PES) is determined as a function of the HO–H and OH–Ar coordinates. This PES is then employed in a wave-packet calculation to determine spectral properties of the system and to calculate the IR absorption spectrum. The vibrational energy levels and relative IR intensities agree well with the experimental spectrum reported earlier. On the other hand, the predissociation lifetimes in the nanosecond regime derived from the 2D PES are in disagreement with the experimental observations, indicating the importance of the neglected degrees of freedom for a correct description of the dynamics of the complex. © 2004 American Institute of Physics.
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33.20.Ea Infrared spectra
33.80.Gj Diffuse spectra; predissociation, photodissociation
33.20.Tp Vibrational analysis
31.15.A- Ab initio calculations
34.20.-b Interatomic and intermolecular potentials and forces, potential energy surfaces for collisions
33.70.Fd Absolute and relative line and band intensities
33.15.Fm Bond strengths, dissociation energies
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