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Journal of Chemical Physics

Wenhui Mi, Alessandro Genova, Michele Pavanello
Since the seminal studies of Thomas and Fermi, researchers in the Density-Functional Theory (DFT) community are searching for accurate electron density functionals. Arguably, the toughest functional to approximate is the noninteracting kinetic energy, Ts [ρ], the subject of this work. The typical paradigm is to first approximate the energy functional and then take its functional derivative, δTs [ρ]δρ(r), yielding a potential that can be used in orbital-free DFT or subsystem DFT simulations. Here, this paradigm is challenged by constructing the potential from the second-functional derivative via functional integration...
May 14, 2018: Journal of Chemical Physics
Roland R Netz
An exactly solvable, Hamiltonian-based model of many massive particles that are coupled by harmonic potentials and driven by stochastic non-equilibrium forces is introduced. The stationary distribution and the fluctuation-dissipation relation are derived in closed form for the general non-equilibrium case. Deviations from equilibrium are on one hand characterized by the difference of the obtained stationary distribution from the Boltzmann distribution; this is possible because the model derives from a particle Hamiltonian...
May 14, 2018: Journal of Chemical Physics
Roberto Luiz A Haiduke, Rodney J Bartlett
Some of the exact conditions provided by the correlated orbital theory are employed to propose new non-empirical parameterizations for exchange-correlation functionals from Density Functional Theory (DFT). This reparameterization process is based on range-separated functionals with 100% exact exchange for long-range interelectronic interactions. The functionals developed here, CAM-QTP-02 and LC-QTP, show mitigated self-interaction error, correctly predict vertical ionization potentials as the negative of eigenvalues for occupied orbitals, and provide nice excitation energies, even for challenging charge-transfer excited states...
May 14, 2018: Journal of Chemical Physics
Justin Provazza, David F Coker
The symmetrical quasi-classical approach for propagation of a many degree of freedom density matrix is explored in the context of computing linear spectra. Calculations on a simple two state model for which exact results are available suggest that the approach gives a qualitative description of peak positions, relative amplitudes, and line broadening. Short time details in the computed dipole autocorrelation function result in exaggerated tails in the spectrum.
May 14, 2018: Journal of Chemical Physics
Daniel S Kosov
We present a theoretical approach to solve the Markovian master equation for quantum transport with stochastic telegraph noise. Considering probabilities as functionals of a random telegraph process, we use Novikov's functional method to convert the stochastic master equation to a set of deterministic differential equations. The equations are then solved in the Laplace space, and the expression for the probability vector averaged over the ensemble of realisations of the stochastic process is obtained. We apply the theory to study the manifestations of telegraph noise in the transport properties of molecular junctions...
May 14, 2018: Journal of Chemical Physics
Dongzheng Yang, Jing Huang, Junxiang Zuo, Xixi Hu, Daiqian Xie
A full-dimensional ab initio potential energy surface for the H2 -HF van der Waals complex was constructed by employing the coupled-cluster singles and doubles with noniterative inclusion of connected triples with augmented correlation-consistent polarised valence quadruple-zeta basis set plus bond functions. Using the improved coupled-states approximation including the nearest neighbor Coriolis couplings, we calculated the state-to-state scattering dynamics for pure rotational and ro-vibrational energy transfer processes...
May 14, 2018: Journal of Chemical Physics
Minglang Wang, Hao Wang, Guangping Zhang, Yongfeng Wang, Stefano Sanvito, Shimin Hou
The relationship between the molecular structure and the electronic transport properties of molecular junctions based on thiol-terminated oligoethers, which are obtained by replacing every third methylene unit in the corresponding alkanethiols with an oxygen atom, is investigated by employing the non-equilibrium Green's function formalism combined with density functional theory. Our calculations show that the low-bias conductance depends strongly on the conformation of the oligoethers in the junction. Specifically, in the cases of trans-extended conformation, the oxygen-dominated transmission peaks are very sharp and well below the Fermi energy, EF , thus hardly affect the transmission around EF ; the Au-S interface hybrid states couple with σ-bonds in the molecular backbone forming the conduction channel at EF , resulting in a conductance decay against the molecular length close to that for alkanethiols...
May 14, 2018: Journal of Chemical Physics
Leah G Dodson, John D Savee, Samer Gozem, Linhan Shen, Anna I Krylov, Craig A Taatjes, David L Osborn, Mitchio Okumura
The absolute photoionization spectrum of the hydroxyl (OH) radical from 12.513 to 14.213 eV was measured by multiplexed photoionization mass spectrometry with time-resolved radical kinetics. Tunable vacuum ultraviolet (VUV) synchrotron radiation was generated at the Advanced Light Source. OH radicals were generated from the reaction of O(1 D) + H2 O in a flow reactor in He at 8 Torr. The initial O(1 D) concentration, where the atom was formed by pulsed laser photolysis of ozone, was determined from the measured depletion of a known concentration of ozone...
May 14, 2018: Journal of Chemical Physics
Daniel Finkelstein-Shapiro, Tõnu Pullerits, Thorsten Hansen
Fano interferences in nanostructures are influenced by dissipation effects as well as many-body interactions. Two-dimensional coherent spectroscopies have just begun to be applied to these systems where the spectroscopic signatures of a discrete-continuum structure are not known. In this article, we calculate the excited-state absorption contribution for different models of higher lying excited states. We find that the characteristic asymmetry of one-dimensional spectroscopies is recovered from the many-body contributions and that the higher lying excited manifolds have distorted lineshapes that are not anticipated from discrete-level Hamiltonians...
May 14, 2018: Journal of Chemical Physics
Ying Yuan, Jicun Li, Xin-Zheng Li, Feng Wang
The development of effective centroid potentials (ECPs) is explored with both the constrained-centroid and quasi-adiabatic force matching using liquid water as a test system. A trajectory integrated with the ECP is free of statistical noises that would be introduced when the centroid potential is approximated on the fly with a finite number of beads. With the reduced cost of ECP, challenging experimental properties can be studied in the spirit of centroid molecular dynamics. The experimental number density of H2 O is 0...
May 14, 2018: Journal of Chemical Physics
Thomas M Miller, Albert A Viggiano, Nicholas S Shuman
The kinetics of thermal electron attachment to methyl thiocyanate (CH3 SCN), methyl isothiocyanate (CH3 NCS), and ethyl thiocyanate (C2 H5 SCN) were measured using flowing afterglow-Langmuir probe apparatuses at temperatures between 300 and 1000 K. CH3 SCN and C2 H5 SCN undergo inefficient dissociative attachment to yield primarily SCN- at 300 K (k = 2 × 10-10 cm3 s-1 ), with increasing efficiency as temperature increases. The increase is well described by activation energies of 0.17 eV (CH3 SCN) and 0.14 eV (C2 H5 SCN)...
May 14, 2018: Journal of Chemical Physics
Abhishek K Sharma, Fernando A Escobedo
Classical Nucleation Theory (CNT) has recently been used in conjunction with a seeding approach to simulate nucleation phenomena at small-to-moderate supersaturation conditions when large free-energy barriers ensue. In this study, the conventional seeding approach [J. R. Espinosa et al., J. Chem. Phys. 144, 034501 (2016)] is improved by a novel, more robust method to estimate nucleation barriers. Inspired by the interfacial pinning approach [U. R. Pedersen, J. Chem. Phys. 139, 104102 (2013)] used before to determine conditions where two phases coexist, the seed of the incipient phase is pinned to a preselected size to iteratively drive the system toward the conditions where the seed becomes a critical nucleus...
May 14, 2018: Journal of Chemical Physics
Pavlos S Stephanou, Martin Kröger
The steady-state extensional viscosity of dense polymeric liquids in elongational flows is known to be peculiar in the sense that for entangled polymer melts it monotonically decreases-whereas for concentrated polymer solutions it increases-with increasing strain rate beyond the inverse Rouse time. To shed light on this issue, we solve the kinetic theory model for concentrated polymer solutions and entangled melts proposed by Curtiss and Bird, also known as the tumbling-snake model, supplemented by a variable link tension coefficient that we relate to the uniaxial nematic order parameter of the polymer...
May 14, 2018: Journal of Chemical Physics
Min Li, Qi Wei
The Electric Stark effect of a Kramers-Henneberger (KH) state of hydrogen atoms in both linearly and circularly polarized laser fields is studied. For the ground KH state of H atoms with a small quiver amplitude, the quadratic Stark effect is observed. For a large quiver amplitude, the Stark effect is quadratic only in a weak electric field and quickly changes to linear as the electric field increases. The atomic structure of the KH state is very sensitive to the electric field and can be easily polarized. The huge polarizability and induced dipole moment are comparable to those of Rydberg atoms...
May 14, 2018: Journal of Chemical Physics
É Pópity-Tóth, G Schuszter, D Horváth, Á Tóth
Complex structures in nature are often formed by self-assembly. In order to mimic the formation, to enhance the production, or to modify the structures, easy-to-use methods are sought to couple engineering and self-assembly. Chemical-garden-like precipitation reactions are frequently used to study such couplings because of the intrinsic chemical and hydrodynamic interplays. In this work, we present a simple method of applying periodic pressure fluctuations given by a peristaltic pump which can be used to achieve regularly banded precipitate membranes in the copper-phosphate system...
May 14, 2018: Journal of Chemical Physics
Mario Motta, Shiwei Zhang
We propose an algorithm for accurate, systematic, and scalable computation of interatomic forces within the auxiliary-field quantum Monte Carlo (AFQMC) method. The algorithm relies on the Hellmann-Feynman theorem and incorporates Pulay corrections in the presence of atomic orbital basis sets. We benchmark the method for small molecules by comparing the computed forces with the derivatives of the AFQMC potential energy surface and by direct comparison with other quantum chemistry methods. We then perform geometry optimizations using the steepest descent algorithm in larger molecules...
May 14, 2018: Journal of Chemical Physics
Chao Liu, Yangyang Zhang, Jian Zhang, Jun Wang, Wenfei Li, Wei Wang
Understanding the microscopic mechanism of water molecular translational diffusion is a challenging topic in both physics and chemistry. Here, we report an investigation on the interplay between the translational diffusion and the large-amplitude angular jumps of water molecules in bulk water using molecular dynamics simulations. We found that large-amplitude angular jumps are tightly coupled to the translational diffusions. Particularly, we revealed that concurrent rotational jumps of spatially neighboring water molecules induce inter-basin translational jumps, which contributes to the fast component of the water translational diffusion...
May 14, 2018: Journal of Chemical Physics
Nadia Ben Amor, Sophie Hoyau, Daniel Maynau, Valérie Brenner
A benchmark set of relevant geometries of a model protein, the N-acetylphenylalanylamide, is presented to assess the validity of the approximate second-order coupled cluster (CC2) method in studying low-lying excited states of such bio-relevant systems. The studies comprise investigations of basis-set dependence as well as comparison with two multireference methods, the multistate complete active space 2nd order perturbation theory (MS-CASPT2) and the multireference difference dedicated configuration interaction (DDCI) methods...
May 14, 2018: Journal of Chemical Physics
Minhaeng Cho
Parametric down-conversion is a second-order nonlinear optical process annihilating a pump photon and creating a pair of photons in the signal and idler modes. Then, by using two parametric down-converters and introducing a path indistinguishability for the two generated idler modes, a quantum coherence between two conjugate signal beams can be induced. Such a double spontaneous or stimulated parametric down-conversion scheme has been used to demonstrate quantum spectroscopy and imaging with undetected idler photons via measuring one-photon interference between their correlated signal beams...
May 14, 2018: Journal of Chemical Physics
A E K Sundén, K Støchkel, P Hvelplund, S Brøndsted Nielsen, B Dynefors, K Hansen
Branching ratios of water and ammonia evaporation have been measured for spontaneous evaporation from protonated mixed clusters H+ (H2 O)n (NH3 )m in the size range 0 ≤ n ≤ 11 and 0 ≤ m ≤ 7. Mixed clusters evaporate water except for clusters containing six or more ammonia molecules, indicating the formation of a stable core of one ammonium ion surrounded by four ammonia molecules and a second shell consisting predominantly of water. We relate evaporative branching ratios to free energy differences between the products of competing channels and determine the free energy differences for clusters with up to seven ammonia molecules...
May 14, 2018: Journal of Chemical Physics
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