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The Journal of Chemical Physics Collection (48 Books)


 
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The Journal of Chemical Physics : Precision shooting: Sampling lon...

By: Michael Grünwald, Christoph Dellago, and Phillip L. Geissler

Description: The kinetics of collective rearrangements in solution, such as protein folding and nanocrystal phase transitions, often involve free energy barriers that are both long and rough. Applying methods of transition path sampling to harvest simulated trajectories that exemplify such processes is typically made difficult by a very low acceptance rate for newly generated trajectories. We address this problem by introducing a new generation algorithm based on the lin...

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The Journal of Chemical Physics : Optimized effective potentials f...

By: Tim Heaton-Burgess and Weitao Yang

Description: We investigate the use of a regularized optimized effective potential (OEP) energy functional and L-curve procedure [ T. Heaton-Burgess, F. A. Bulat, and W. Yang, Phys. Rev. Lett. 98, 256401 (2007) ] for determining physically meaningful OEPs from arbitrary combinations of finite orbital and potential basis sets. The important issue of the manner in which the optimal regularization parameter is determined from the L-curve perspective is reconsidered with the...

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The Journal of Chemical Physics : Optimal alignment control of a n...

By: Kazuyuki Nakagami, Yoshihiko Mizumoto, and Yukiyoshi Ohtsuki

Description: Alignment control of an ensemble of nonpolar molecules is numerically studied by means of optimal control simulation. A nitrogen molecule that is modeled by a quantum rigid rotor is adopted. Controlled rotational wave packets are created through nonresonant optical transitions induced by polarizability coupling. Optimal pulses are designed to achieve the alignment control at a specified time in the absence/presence of external static fields in zero- and fini...

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The Journal of Chemical Physics : Coarse grained open system quant...

By: Ioannis Thanopulos, Paul Brumer, and Moshe Shapiro

Description: We show that the quantum dynamics of a system comprised of a subspace Q coupled to a larger subspace P can be recast as a reduced set of “coarse grained” ordinary differential equations with constant coefficients. These equations can be solved by a single diagonalization of a general complex matrix. The method makes no assumptions about the strength of the couplings between the Q and the P subspaces, nor is there any limitation on the initial population in P...

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The Journal of Chemical Physics : A noniterative perturbative trip...

By: Prashant U. Manohar and Anna I. Krylov

Description: A noniterative N 7 triples correction for the equation-of-motion coupled-cluster method with single and double substitutions (CCSD) is presented. The correction is derived by second-order perturbation treatment of the similarity-transformed CCSD Hamiltonian. The spin-conserving variant of the correction is identical to the triples correction of Piecuch and co-workers [Mol. Phys. 104, 2149 (2006) ] derived within method-of-moments framework and is not size in...

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The Journal of Chemical Physics : Perturbative calculation of spin...

By: Kerstin Klein and Jürgen Gauss

Description: Spin-orbit splittings for 2Π states are calculated within coupled-cluster (CC) theory via first-order degenerate perturbation theory. Using the equation-of-motion CC variant for ionization potentials (EOMIP-CC), the two components of the considered 2Π state are treated in a balanced way by generating both radical states via annihilation of one electron out of the CC wave function of the corresponding anion. We report on the implementation of the described ap...

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The Journal of Chemical Physics : Magnetic exchange couplings from...

By: Juan E. Peralta and Veronica Barone

Description: We propose a method for the evaluation of magnetic exchange couplings based on noncollinear spin density functional calculations. The method employs the second derivative of the total Kohn–Sham energy of a single reference state, in contrast to approximations based on Kohn–Sham total energy differences. The advantage of our approach is twofold: It provides a physically motivated picture of the transition from a low-spin to a high-spin state, and it utilizes ...

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The Journal of Chemical Physics : Optical absorption of small silv...

By: M. Harb, F. Rabilloud, D. Simon, A. Rydlo, S. Lecoultre et al

Description: We present a joint theoretical and experimental investigation of the absorption spectra of silver clusters Agn (4 ≤ n ≤ 22). The experimental spectra of clusters isolated in an Ar matrix are compared with the calculated ones in the framework of the time-dependent density functional theory. The analysis of the molecular transitions indicates that the s-electrons are responsible for the optical response of small clusters (n ≤ 8) while the d-electrons play a cr...

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The Journal of Chemical Physics : An efficient implementation for ...

By: Marius J. Vilkas and Chang-Guo Zhan

Description: An efficient algorithm of the surface and volume polarization for electrostatics (SVPE) method in self-consistent reaction field (SCRF) theory, denoted by SV(1)PE, has been proposed to simulate direct volume polarization potential with a single layer of point charges outside the solute cavity while the indirect effects of volume polarization on surface polarization are still simulated with multiple layers of point charges. The free energies of solvation calc...

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The Journal of Chemical Physics : First-principles study of therma...

By: Jun-Ho Lee, Ji Young Lee, and Jun-Hyung Cho

Description: Using first-principles density-functional calculations, we investigate the reaction of acetone on the Si(001) surface, which exhibits the conversion from a kinetically controlled reaction to thermodynamically controlled one by means of thermal anneal or the highly confined electron beam of the scanning tunneling microscopy (STM) tip. We identified the four different reaction pathways forming not only two kinds of di-σ structures on top of a single Si dimer (...

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The Journal of Chemical Physics : On the accuracy of density-funct...

By: Biswajit Santra, Angelos Michaelides, Martin Fuchs, Alexandre Tkatchenko, Claudia Filippi et al

Description: Second order Møller–Plesset perturbation theory at the complete basis set limit and diffusion quantum Monte Carlo are used to examine several low energy isomers of the water hexamer. Both approaches predict the so-called prism to be the lowest energy isomer, followed by cage, book, and cyclic isomers. The energies of the four isomers are very similar, all being within 10–15 meV/H2O. These reference data are then used to evaluate the performance of several de...

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The Journal of Chemical Physics : Quantum trajectory calculations ...

By: Kisam Park, Bill Poirier, and Gérard Parlant

Description: Quantum trajectory methods (QTMs) hold great promise as a potential means of obtaining dynamical insight and computational scaling similar to classical trajectory simulations but in an exact quantum dynamical context. To date, the development of QTMs has been stymied by the “node problem”—highly nonclassical and numerically unstable trajectories that arise when the wavepacket density |ψ|2 exhibits substantial interference oscillations. In a recent paper, how...

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The Journal of Chemical Physics : Nonlinear quantum time correlati...

By: Francesco Paesani and Gregory A. Voth

Description: A new approach for the calculation of nonlinear quantum time correlation functions within the path-integral centroid dynamics formalism is presented. This approach combines information on the real-time dynamics obtained from centroid molecular dynamics with classical operators with information on the corresponding imaginary-time dynamics obtained from path-integral molecular dynamics. Nonlinear quantum correlation functions in the high and low temperature re...

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The Journal of Chemical Physics : Exact integral constraint requir...

By: N. H. March and Á. Nagy

Description: Following some studies of ∫ n(r)∇V(r)dr by earlier workers for the density functional theory (DFT) one-body potential V(r) generating the exact ground-state density, we consider here the special case of spherical atoms. The starting point is the differential virial theorem, which is used, as well as the Hiller–Sucher–Feinberg [ Phys. Rev. A 18, 2399 (1978) ] identity to show that the scalar quantity paralleling the above vector integral, namely, ∫ n(r)∂V(r)/...

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The Journal of Chemical Physics : The CCSD(T) complete basis set l...

By: Ericka C. Barnes, George A. Petersson, David Feller, and Kirk A. Peterson

Description: Recent estimates of the CCSD(T)(FC) limit for the neon atom (−128.8690±0.001 and −128.8687±0.0005 hartree) are refined. Re-examination of the basis set convergence of the separate self-consistent field, MP2-αβ, MP2-αα, CCSD–MP2, and (T) components of the valence CCSD(T) energy gives a complete basis set limit of −128.869 236±0.000 02 hartree. This can now be used as an improved benchmark to calibrate more approximate calculations.

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The Journal of Chemical Physics : Analysis of polyatomic molecules...

By: Peter C. Chen and Kamilah Mitchell

Description: The peak-sorting capabilities of high resolution coherent two-dimensional (2D) spectroscopy provide a new way of dealing with severe rotational congestion. This paper describes the application of this technique to the polyatomic molecule, NO2. NO2 is a primary component of photochemical smog and has a notoriously complex and congested spectrum that extends from the infrared to the ultraviolet regions. This spectrum is infamous for having an unusually high de...

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The Journal of Chemical Physics : Melting scenario in metallic clu...

By: P. J. Hsu, J. S. Luo, S. K. Lai, J. F. Wax, and J.-L. Bretonnet

Description: The isothermal Brownian-type molecular dynamics simulation has been applied to study the melting behavior of bimetallic clusters. It was found that the specific heat and Lindermann-like parameter customarily used in bulk system to describe solid-liquid transition show incongruity in the predicted melting temperature Tmelt. The underlying mechanisms that lead to the incompatibility of Tmelt separately deduced from these two quantities were analyzed further. T...

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The Journal of Chemical Physics : Kinetic and theoretical study of...

By: Andrés Garzón, José Albaladejo, Alberto Notario, Tomás Peña-Ruiz, and Manuel Fernández-Gómez

Description: The reactions of Cl with a series of linear thiols: 1-propanethiol (k1), 1-butanethiol (k2), and 1-pentanethiol (k3) were investigated as a function of temperature (in the range of 268–379 K) and pressure (in the range of 50–200 Torr) by laser photolysis-resonance fluorescence. Only 1-propanethiol has previously been studied, but at 1 Torr of total pressure. The derived Arrhenius expressions obtained using our kinetic data were as follows: k1 = (3.97±0.44)×1...

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The Journal of Chemical Physics : Photodissociation dynamics of me...

By: Shih-Huang Lee

Description: We investigated the photodissociation dynamics of methyl formate-d (CH3OC(O)D) at 193.3 nm in a molecular-beam apparatus using undulator radiation as an ionization source. We measured kinetic-energy distributions, spatial angular anisotropies, and branching ratios of all photofragments. Fractions of energy release into product translation were calculated from the kinetic-energy distributions. Four primary dissociation pathways to asymptotes CH3O( 2E)+DCO( 2A...

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The Journal of Chemical Physics : The multiconfigurational-referen...

By: Jirí Czernek and Oldrich Živný

Description: The multiconfigurational-reference internally contracted configuration interaction (MRCI)/aug-cc-pVQZ-based computational protocol was employed to search for the minima of the potential energy surface of the low-lying singlet and triplet electronic states of the trifluoride anion F3− in the D∞h, C∞v, C2v, and Cs symmetry groups. The 2 bound state was located (re = 1.8777 Å and θ = 103.39°), which was predicted to lie less than 1 eV above the X g+ ground stat...

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