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Journal of Chemical Physics

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https://www.readbyqxmd.com/read/28201921/generalized-spin-ratio-scaled-mp2-method-for-accurate-prediction-of-intermolecular-interactions-for-neutral-and-ionic-species
#1
Samuel Tan, Santiago Barrera Acevedo, Ekaterina I Izgorodina
The accurate calculation of intermolecular interactions is important to our understanding of properties in large molecular systems. The high computational cost of the current "gold standard" method, coupled cluster with singles and doubles and perturbative triples (CCSD(T), limits its application to small- to medium-sized systems. Second-order Møller-Plesset perturbation (MP2) theory is a cheaper alternative for larger systems, although at the expense of its decreased accuracy, especially when treating van der Waals complexes...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201920/atomic-vs-quantum-dot-open-shell-spectra
#2
Jacob Katriel, H E Montgomery
Hund's rules apply to pairs of atomic states which, in the limit of weak interelectronic repulsion, belong to a common configuration. We examine the asymptotic behavior of the energy difference between states belonging to such pairs (ΔE) as a function of the nuclear charge (Z) at both Z→∞ (ignoring relativistic effects) and at Z→Zc, where Zc is the critical charge below which the outermost electron is not bound. We find that the ratio ΔEZ(2) is non-monotonic, having a maximum at some intermediate value of Z...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201919/new-insights-into-mechanistic-photoisomerization-of-ethylene-bridged-azobenzene-from-ab-initio-multiple-spawning-simulation
#3
Lihong Liu, Yating Wang, Qiu Fang
Ethylene-bridged azobenzene (br-AB) has aroused broad interests due to its unique photoswitching properties. Numerous dynamical simulations have been performed for the br-AB photoisomerization, which focused mainly on the conformational effect and the funnel role of minimum-energy conical intersection (MECI) on the mechanism. In the present work, we use the "full quantum" ab initio multiple spawning method to simulate the br-AB photoisomerization, which provides new insights into the mechanism. Upon irradiation of br-AB to the first excited singlet state (S1), most of the excess energies are trapped in the azo-moiety...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201918/a-comparative-first-principles-study-of-the-structural-and-electronic-properties-of-the-liquid-li-si-and-li-ge-alloys
#4
Han-Hsin Chiang, Chin-Lung Kuo
We have performed a comparative first-principles study on the structural and electronic properties of the liquid Li1-xSix and Li1-xGex alloys over a range of composition from x = 0.09 to 0.50. Our calculations showed that Si and Ge atoms can exhibit very distinct local bonding characteristics as they were alloyed with the Li atoms in the liquid state, where Si atoms tended to form a variety of covalent bonding configurations while Ge atoms predominantly appeared as the isolated anions in the liquid alloys. These differences in bonding characteristics were reflected in their electronic density of states, in which the liquid Li1-xGex alloys have a lower degree of s-p hybridization with narrower distributions of the 3s and 3p states than the liquid Li1-xSix alloys...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201917/parallel-tempering-monte-carlo-combined-with-clustering-euclidean-metric-analysis-to-study-the-thermodynamic-stability-of-lennard-jones-nanoclusters
#5
Henrique M Cezar, Gustavo G Rondina, Juarez L F Da Silva
A basic requirement for an atom-level understanding of nanoclusters is the knowledge of their atomic structure. This understanding is incomplete if it does not take into account temperature effects, which play a crucial role in phase transitions and changes in the overall stability of the particles. Finite size particles present intricate potential energy surfaces, and rigorous descriptions of temperature effects are best achieved by exploiting extended ensemble algorithms, such as the Parallel Tempering Monte Carlo (PTMC)...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201916/artificial-neural-network-for-the-configuration-problem-in-solids
#6
Hyunjun Ji, Yousung Jung
A machine learning approach based on the artificial neural network (ANN) is applied for the configuration problem in solids. The proposed method provides a direct mapping from configuration vectors to energies. The benchmark conducted for the M1 phase of Mo-V-Te-Nb oxide showed that only a fraction of configurations needs to be calculated, thus the computational burden significantly decreased, by a factor of 20-50, with R(2) = 0.96 and MAD = 0.12 eV. It is shown that ANN can also handle the effects of geometry relaxation when properly trained, resulting in R(2) = 0...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201915/2d-lattice-model-of-a-lipid-bilayer-microscopic-derivation-and-thermodynamic-exploration
#7
Davit Hakobyan, Andreas Heuer
Based on all-atom Molecular Dynamics (MD) simulations of a lipid bilayer we present a systematic mapping on a 2D lattice model. Keeping the lipid type and the chain order parameter as key variables we derive a free energy functional, containing the enthalpic interaction of adjacent lipids as well as the tail entropy. The functional form of both functions is explicitly determined for saturated and polyunsaturated lipids. By studying the lattice model via Monte Carlo simulations it is possible to reproduce the temperature dependence of the distribution of order parameters of the pure lipids, including the prediction of the gel transition...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201914/macroscopic-dielectric-function-within-time-dependent-density-functional-theory-real-time-evolution-versus-the-casida-approach
#8
Tobias Sander, Georg Kresse
Linear optical properties can be calculated by solving the time-dependent density functional theory equations. Linearization of the equation of motion around the ground state orbitals results in the so-called Casida equation, which is formally very similar to the Bethe-Salpeter equation. Alternatively one can determine the spectral functions by applying an infinitely short electric field in time and then following the evolution of the electron orbitals and the evolution of the dipole moments. The long wavelength response function is then given by the Fourier transformation of the evolution of the dipole moments in time...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201913/reaction-rates-for-reaction-diffusion-kinetics-on-unstructured-meshes
#9
Stefan Hellander, Linda Petzold
The reaction-diffusion master equation is a stochastic model often utilized in the study of biochemical reaction networks in living cells. It is applied when the spatial distribution of molecules is important to the dynamics of the system. A viable approach to resolve the complex geometry of cells accurately is to discretize space with an unstructured mesh. Diffusion is modeled as discrete jumps between nodes on the mesh, and the diffusion jump rates can be obtained through a discretization of the diffusion equation on the mesh...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201912/free-energy-functionals-for-polarization-fluctuations-pekar-factor-revisited
#10
Mohammadhasan Dinpajooh, Marshall D Newton, Dmitry V Matyushov
The separation of slow nuclear and fast electronic polarization in problems related to electron mobility in polarizable media was considered by Pekar 70 years ago. Within dielectric continuum models, this separation leads to the Pekar factor in the free energy of solvation by the nuclear degrees of freedom. The main qualitative prediction of Pekar's perspective is a significant, by about a factor of two, drop of the nuclear solvation free energy compared to the total (electronic plus nuclear) free energy of solvation...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201911/semi-empirical-refinements-of-crystal-structures-using-17-o-quadrupolar-coupling-tensors
#11
Sean T Holmes, Robbie J Iuliucci, Karl T Mueller, Cecil Dybowski
We demonstrate a modification of Grimme's two-parameter empirical dispersion force field (referred to as the PW91-D2* method), in which the damping function has been optimized to yield geometries that result in predictions of the principal values of (17)O quadrupolar-coupling tensors that are systematically in close agreement with experiment. The predictions of (17)O quadrupolar-coupling tensors using PW91-D2*-refined structures yield a root-mean-square deviation (RMSD) (0.28 MHz) for twenty-two crystalline systems that is smaller than the RMSD for predictions based on X-ray diffraction structures (0...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201910/mode-specific-excited-state-dynamics-study-of-bis-phenylethynyl-benzene-from-ultrafast-raman-loss-spectroscopy
#12
Khokan Roy, Surajit Kayal, Freek Ariese, Andrew Beeby, Siva Umapathy
Femtosecond transient absorption (fs-TA) and Ultrafast Raman Loss Spectroscopy (URLS) have been applied to reveal the excited state dynamics of bis(phenylethynyl)benzene (BPEB), a model system for one-dimensional molecular wires that have numerous applications in opto-electronics. It is known from the literature that in the ground state BPEB has a low torsional barrier, resulting in a mixed population of rotamers in solution at room temperature. For the excited state this torsional barrier had been calculated to be much higher...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201909/evaluation-of-the-quasi-correlated-tight-binding-qctb-model-for-describing-polyradical-character-in-polycyclic-hydrocarbons
#13
Anatoliy V Luzanov, Felix Plasser, Anita Das, Hans Lischka
We present a verification and significant algorithmic improvement of the quasi-correlation tight-binding (QCTB) scheme (a Hückel-Hubbard-type model mimicking electron correlation) for describing effectively unpaired electrons in the spirit of Head-Gordon's approach [M. Head-Gordon, Chem. Phys. Lett. 380, 488 (2003)]. For comparison purposes, results based on the high-level ab initio multireference averaged quadratic coupled cluster method previously computed in our works are invoked. In doing so, typical polyaromatic hydrocarbons (polyacenes, periacenes, zethrenes, and the Clar goblet) are studied...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201908/electron-correlation-by-polarization-of-interacting-densities
#14
Jerry L Whitten
Coulomb interactions that occur in electronic structure calculations are correlated by allowing basis function components of the interacting densities to polarize dynamically, thereby reducing the magnitude of the interaction. Exchange integrals of molecular orbitals are not correlated. The modified Coulomb interactions are used in single-determinant or configuration interaction calculations. The objective is to account for dynamical correlation effects without explicitly introducing higher spherical harmonic functions into the molecular orbital basis...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201907/improved-virtual-orbitals-in-state-specific-multireference-perturbation-theory-for-prototypes-of-quasidegenerate-electronic-structure
#15
Suvonil Sinha Ray, Pradipta Ghosh, Rajat K Chaudhuri, Sudip Chattopadhyay
The state-specific multireference perturbation theory (SSMRPT) with an improved virtual orbital complete active space configuration interaction (IVO-CASCI) reference function [called as IVO-SSMRPT] is used to investigate the energy surface, geometrical parameters, molecular properties of spectroscopic interest for the systems/situations [such as BeH2, BeCH2, MgCH2, Si2H4, unimolecular dissociation of H2CO, and intramolecular reaction pathways of 1,3-butadiene] where the effect of quasidegeneracy cannot be neglected...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201906/publisher-s-note-finite-size-scaling-study-of-dynamic-critical-phenomena-in-a-vapor-liquid-transition-j-chem-phys-146-044503-2017
#16
Jiarul Midya, Subir K Das
No abstract text is available yet for this article.
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201905/accurate-ab-initio-dipole-moment-surfaces-of-ozone-first-principle-intensity-predictions-for-rotationally-resolved-spectra-in-a-large-range-of-overtone-and-combination-bands
#17
Vladimir G Tyuterev, Roman V Kochanov, Sergey A Tashkun
Ab initio dipole moment surfaces (DMSs) of the ozone molecule are computed using the MRCI-SD method with AVQZ, AV5Z, and VQZ-F12 basis sets on a dense grid of about 1950 geometrical configurations. The analytical DMS representation used for the fit of ab initio points provides better behavior for large nuclear displacements than that of previous studies. Various DMS models were derived and tested. Vibration-rotation line intensities of (16)O3 were calculated from these ab initio surfaces by the variational method using two different potential functions determined in our previous works...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201904/relaxation-time-and-excess-entropy-in-viscous-liquids-electric-field-versus-temperature-as-control-parameter
#18
Ranko Richert
On the basis of adiabatic calorimetry data and results obtained from dielectric relaxation studies in the presence of a high static electric field, the effects of temperature and electric field induced changes of the excess entropy are compared for the same sample: supercooled cresolphthalein dimethylether. A field induced reduction of the excess entropy by 45 mJ K(-1) mol(-1) at constant temperature increases the structural relaxation time by 0.75%, while the same entropy change originating from lowering the temperature at constant field increases the time constant by 3...
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201903/ultrafast-internal-conversion-dynamics-of-highly-excited-pyrrole-studied-with-vuv-uv-pump-probe-spectroscopy
#19
Spencer L Horton, Yusong Liu, Pratip Chakraborty, Spiridoula Matsika, Thomas Weinacht
We study the relaxation dynamics of pyrrole after excitation with an 8 eV pump pulse to a state just 0.2 eV below the ionization potential using vacuum ultraviolet/ultraviolet pump probe spectroscopy. Our measurements in conjunction with electronic structure calculations indicate that pyrrole undergoes rapid internal conversion to the ground state in less than 300 fs. We find that internal conversion to the ground state dominates over dissociation.
February 14, 2017: Journal of Chemical Physics
https://www.readbyqxmd.com/read/28201902/graphene-contacts-to-a-hfse2-sns2-heterostructure
#20
Shanshan Su, Protik Das, Supeng Ge, Roger K Lake
Two-dimensional (2D) heterostructures and all-2D contacts are of high interest for electronic device applications, and the SnS2/HfSe2 bilayer heterostructure with graphene contacts has some unique, advantageous properties. The SnS2/HfSe2 heterostructure is interesting because of the strong intermixing of the two conduction bands and the large work function of the SnS2. The band lineup of the well separated materials indicates a type II heterostructure, but the conduction band minimum of the SnS2/HfSe2 bilayer is a coherent superposition of the orbitals from the two layers with a spectral weight of 60% on the SnS2 and 40% on the HfSe2 for AA stacking...
February 14, 2017: Journal of Chemical Physics
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