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  • Band Structures Tuning for 2D Porous Graphene-like Sheets with Specific CN Stoichiometric Ratio: Theoretical Investigation
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-13
    Chunhua Yang, Zhao-Di Yang, Rui Zhang, Guiling Zhang

    2D porous graphene-like sheets with specific CN stoichiometric ratio (h-C2N and h-C5N2) were theoretically investigated based on DFT method. The calculated results show h-C2N and h-C5N2 are both semiconductors with direct band gap 1.72 and 1.10 eV. The CBM positon for h-C2N is high, but the potential positions for h-C5N2 are very low. h-C2N is predicted as good photo- or electro-catalyst to produce hydrogen or CO2 reduction but h-C5N2 is not. Defects construction and tailoring 2D h-C2N and h-C5N2 sheets to 1D nanoribbons were used to tune the band structures. The defective derivatives are n-type semiconductor with two doping levels contributed by O atoms. The doping levels could capture electrons as trap levels and O atoms could coordinate metal to obtain single-atom catalyst. 1D nanoribbons show bigger band gaps and higher CBM potential position than corresponding 2D sheets, which is thought to show better properties on photo- or electro-catalysis.

    更新日期:2018-10-14
  • Thermodynamics and kinetics of nucleation in binary solutions
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-11
    Nikolay V. Alekseechkin

    A new approach that is a combination of classical thermodynamics and macroscopic kinetics is offered for studying the nucleation kinetics in condensed binary solutions. The theory covers the separation of liquid and solid solutions proceeding along the nucleation mechanism, as well as liquid-solid transformations, e.g., the crystallization of molten alloys. The cases of nucleation of both unary and binary precipitates are considered. Equations of equilibrium for a critical nucleus are derived and then employed in the macroscopic equations of nucleus growth; the steady state nucleation rate is calculated with the use of these equations. The present approach can be applied to the general case of non-ideal solution; the calculations are performed on the model of regular solution within the classical nucleation theory (CNT) approximation implying the bulk properties of a nucleus and constant surface tension. The way of extending the theory beyond the CNT approximation is shown in the framework of the finite-thickness layer method. From equations of equilibrium of a surface layer with coexisting bulk phases, equations for adsorption and the dependences of surface tension on temperature, radius, and composition are derived. Surface effects on the thermodynamics and kinetics of nucleation are discussed.

    更新日期:2018-10-12
  • Thermodynamic properties of interacting like-rod chains: entropic sampling simulations
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-12
    Lucas S. Ferreira, Álvaro A. Caparica, Lucas N. Jorge, Minos A. Neto

    In this work we apply the transfer matrix method to obtain exact solutions for a rod-like interacting unidimensional system and carry out entropic simulations to obtain the same results. A joint density of states is adopted, such that it depends not only of the energy, but also of the total number of dimers and the number of interactions between interacting dimers. We estimate the density of dimers and vacancies, along with the number of interacting links per site, and compare with the exact results. The concordance is excellent.

    更新日期:2018-10-12
  • Multi reference studies of gas phase vanadium nitride di- and trications
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-10
    H. Hendaoui, D. Ben Abdallah, N.E. Jaidane, M. Mogren Al Mogren, S. Almenia, A. Elmarghany, R. Linguerri, M. Hochlaf
    更新日期:2018-10-10
  • Ultrafast N–H vibrational dynamics of hydrogen-bonded cyclic amide reveal by 2DIR spectroscopy
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-05
    Kiran Sankar Maiti

    Hydrogen-bonding strongly influences the vibrational dynamics of the N–H stretch vibration, hence the molecular structure and dynamics. Therefore the N–H stretch vibration is an important probe to study hydrogen-bond dynamics as well as the molecular structure and dynamics, specially for the biological molecule. In this article, the dynamics and couplings of N–H stretching vibrations of biological molecules are investigated with linear infrared spectroscopy and ultrafast two-dimensional infrared (2DIR) spectroscopy with a model molecule 2-Pyrrolidinone. In solution, 2-Pyrrolidinone makes three different kinds of intermolecular hydrogen bonding, whose spectra have been collected with FTIR as well as with 2DIR spectroscopy and discussed. Inter-molecular hydrogen bond making and breaking between N–H and C=O vibrational bands are discussed also.

    更新日期:2018-10-06
  • Thermal Stability of Al-Cu-Fe-Cr-Ni High Entropy Alloy Bulk and Nanoparticle Structure: A Molecular Dynamics Perspective
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-06
    Ziming Zeng, Jianfeng Zhao, Xiaofeng Zhou, Junhua Li, Bodong Liang
    更新日期:2018-10-06
  • Specific solvent effect on the photophysical behavior of substituted chromones: A combined fluorescence, DFT and MD study
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-01
    Mostofa Ataur Rohman, Prayasee Baruah, Semen O. Yesylevskyy, Sivaprasad Mitra
    更新日期:2018-10-02
  • Electronic Structure and Photoelectron Spectroscopy of Manganese Dihalides from Quantum Chemical Methods and Dyson Orbitals
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-01
    Sabyasachi Roy Chowdhury, Soumitra Manna, Sabyashachi Mishra

    Accurate treatment of electron correlation and spin-orbit coupling is essential for understanding the electronic structure and spectroscopy of high-spin, open-shell transition metal dihalides. The experimental photoelectron spectra of MnX2, X= Cl, Br, I, have been interpreted on the basis of multi-configurational ab initio electronic structure calculations. The intensity of the photoelectron bands have been calculated from the norms of the Dyson orbitals, which represent the transition probability to a particular ionic state from a given starting state. The present study provides a detailed account of the contribution of the one- and two-electron transitions in the experimental photoelectron spectra of the title molecules and outlines the nature of the photoelectron bands in terms of the closely spaced quintet and septet states of the cationic species.

    更新日期:2018-10-02
  • Electron Momentum Spectroscopy Study of Outer Valence Electronic Structure of Pyrrole
    Chem. Phys. (IF 1.707) Pub Date : 2018-10-02
    Zhean Li, Yaguo Tang, Zhaohui Liu, Shanshan Niu, Xu Shan, Xiangjun Chen

    The binding energy spectrum and electron momentum distributions (EMDs) for the outer valence shells of pyrrole molecule are measured by a high-sensitivity (e, 2e) spectrometer at incident energy of 1200 eV plus the binding energy employing non-coplanar symmetric kinematic geometry. The obtained EMDs are compared with the theoretical calculations at equilibrium molecular geometry as well as considering vibrational effect by density functional theory method. The result shows that the molecular vibrational motion has obvious influence on EMDs for some of the outer valence orbitals. The controversy over the assignment of the ionization bands, especially the positions of satellite states concerning the ionization of 1b1 orbital, in the binding energy range of 11-16.5 eV has been clarified.

    更新日期:2018-10-02
  • 更新日期:2018-09-29
  • 更新日期:2018-09-29
  • An experimental and DFT study on free radical scavenging activity of hesperetin Schiff bases
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-28
    Anna Sykula, Agnieszka Kowalska-Baron, Aliaksandr Dzeikala, Agnieszka Bodzioch, Elzbieta Lodyga-Chruscinska
    更新日期:2018-09-28
  • 更新日期:2018-09-28
  • Observation by optical second harmonic generation of the mean tilt angle of cyanine dyes during compression with a phase transition in a Langmuir-Blodgett trough
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-28
    Y. Miyauchi, R. Yukutake, K. Tsuchida, Y. Umemura, A. Tsukamoto, T. Suzuki

    Optical second harmonic generation (SHG) signals from a cyanine dye during compression of a monolayer in a Langmuir-Blodgett trough were measured to investigate the mean tilt angle of the dye corresponding to the formation of an H-band. The pressure-surface area (π-A) isotherm for 3,3'-dioctadecyloxacarbocyanine molecules spread on an aqueous subphase showed a plateau region after a kink point in the isotherm characteristic, which suggests a phase transition from the liquid expanded (LE) phase to the liquid condensed (LC) phase. SHG signals from the monolayer were obtained as the surface area decreased for the input and output polarization combinations PP, MS, SP, PS, and SS, where the first and second letters denote the input and output polarizations, respectively, and M refers to the polarization midway between S and P. For polarization combination PP, the SHG signal increased steeply during compression, whereas for polarization combination MS, the signal increased gently. The SH field from the monolayer for polarization combination SP in the LC phase was almost inverted to the field in the LE phase. We estimated the mean polar angles from the SHG responses during compression. The angle decreased continuously by almost 5° from 28° with the growth of domains in the LC phase. Visible absorption spectra of monolayers transferred to glass substrates were also obtained. The area intensity of the peak in the spectra attributed to H-aggregates increased compared with that of the monomer as the surface area decreased in the LC phase. The results were consistent with the polar angle reduction in the LC phase observed by in situ SHG. The decrease of the angle in the LC phase probably allowed the cyanine dyes to pack together tightly and align side by side, promoting H-aggregation.

    更新日期:2018-09-28
  • Exact analytical calculations of thermodynamic functions of gaseous substances
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-26
    R. Khordad, A. Avazpour, A. Ghanbari

    We have considered the improved Tietz potential for diatomic molecules. We have analytically solved the Schrödinger equation for this potential model and derived the analytical expression for the energy spectra. Then, we have analytically obtained the thermodynamic functions for six gaseous substances such as HCl, HF, DF, BBr, CO and NO using the potential model. For this goal, we have calculated mean energy, specific heat, and free energy and compared with experimental data. Our results show that the calculated thermodynamic properties at room temperature are in agreement with experimental data.

    更新日期:2018-09-27
  • An efficient pseudo-spectral method for the description of atomic electronic wave functions -application to the hydrogen atom in a uniform magnetic field
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-27
    Clemens Woywod, Susmita Roy, Kiran Maiti, Kenneth Ruud

    The mapping of an electronic state on a real-space support lattice may offer advantages over a basis set ansatz in cases where there are linear dependences due to basis set overcompleteness or when strong internal or external fields are present. Such discretization methods are also of interest because they allow for the convenient numerical integration of matrix elements of local operators. We have developed a pseudo-spectral approach to the numerical solution of the time-dependent and time-independent Schrödinger equations describing electronic motion in atoms and atomic ions in terms of a spherical coordinate system. A key feature of this scheme is the construction of a Variational Basis Representation (VBR) for the non-local component and of a Generalized Finite Basis Representation (GFBR) for the local component of the electronic Hamiltonian operator. Radial Hamiltonian eigenfunctions χnl;β(r) of the H atom-like system and spherical harmonics form the basis set. Two special cases of this approach are explored: In one case, the functions of the field-free H atom are used as the elements of the basis set, and in the second case, each radial basis function has been obtained by variationally optimizing a shielding parameter β to yield a minimum energy for a particular eigenstate of the H atom in a uniform magnetic field.We derive a new quadrature rule of nearly Gaussian accuracy for the computation of matrix elements of local operators between radial basis functions and perform numerical evaluation of local operator matrix elements involving spherical harmonics. With this combination of radial and angular quadrature prescriptions we ensure to a good approximation the discrete orthogonality of Hamiltonian eigenfunctions of H atom-like systems for summation over the grid points. We further show that sets of χnl;β(r) functions are linearly independent, whereas sets of the polar-angle-dependent components of the spherical harmonics, i.e., the associated Legendre functions, are not and provide a physical interpretation of this mathematical observation.The pseudo-spectral approach presented here is applied to two model systems: the field-free H atom and the H atom in a uniform magnetic field. The results demonstrate the potential of this method for the description of challenging systems such as highly charged atomic ions.

    更新日期:2018-09-27
  • The Ground State Properties of Two Dimensional Fermi Gas System Confined in a Potential Composed of Harmonic and a Gaussian Terms
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-27
    Berna Gülveren, Mehmet Şahin, Ülfet Atav

    In this work, the ground state properties of two dimensional Fermi gas system interacting in a potential consisting of harmonic and Gaussian terms are investigated in the frame of Thomas-Fermi approximation. The depth and the curvature of the potential are changed by varying confinement parameters and the influence of the constraning conditions on the system properties like the density profile, the kinetic and the potential energy of the fermionic system is analyzed comprehensively. The deviations of the results due to the Gaussian potential are also determined by comparing the results with those obtained for pure harmonic potential. Calculations are also performed analytically for non-interacting case for comparative purposes. The results show that the confinement parameters play crucial role on the ground state properties of confined system.

    更新日期:2018-09-27
  • Nonadiabatic Dynamics Simulations of Photoexcited Urocanic Acid
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-25
    Deniz Tuna, Lasse Spörkel, Mario Barbatti, Walter Thiel
    更新日期:2018-09-26
  • Effects of Zn2+ Ion Doping on Hybrid Perovskite Crystallization and Photovoltaic Performance of Solar Cells
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-22
    Meidan Que, Wei Chen, Peng Chen, Jie Liu, Xingtian Yin, Bowen Gao, Wenxiu Que
    更新日期:2018-09-25
  • A DFT investigation exploring the influence of lone electron pair on hyperfine structures of N-centered radicals
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-22
    Chenxuan Zhao, Rina Dao, Yongtao Wang, Jia Yao, Haoran Li
    更新日期:2018-09-25
  • Attractive Bose-Einstein condensates in anharmonic traps: Accurate numerical treatment and the intriguing physics of the variance
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-22
    Ofir E. Alon, Lorenz S. Cederbaum

    The dynamics of attractive bosons trapped in one dimensional anharmonic potentials is investigated. Particular emphasis is put on the variance of the position and momentum many-particle operators. Coupling of the center-of-mass and relative-motion degrees-of-freedom necessitates an accurate numerical treatment. The multiconfigurational time-dependent Hartree for bosons (MCTDHB) method is used, and high convergence of the energy, depletion and occupation numbers, and position and momentum variances is proven numerically. We demonstrate for the ground state and out-of-equilibrium dynamics, for condensed and fragmented condensates, for small systems and en route to the infinite-particle limit, that intriguing differences between the density and variance of an attractive Bose-Einstein condensate emerge. Implications are briefly discussed.

    更新日期:2018-09-25
  • Particles Aggregation and Fragmentation — A Monte Carlo Study
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-22
    Mohsen Zirrahi, Bahareh Azinfar, Hassan Hassanzadeh, Jalal Abedi, Reza Azin, Shahriar Osfouri
    更新日期:2018-09-25
  • Novel Ag2CrO4/Bi2O2CO3 heterojunction: simple preparation, wide visible-light absorption band and excellent photocatalytic activity
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-22
    Hongxia Fan, Hualei Zhou, Hongda Li, Xintong Liu, Chaojun Ren, Fangzhi Wang, Wenjun Li
    更新日期:2018-09-25
  • Evidence for competing proton-transfer and hydrogen-transfer reactions in the S1 state of indigo
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-22
    Michael R. Haggmark, Gregory Gate, Samuel Boldissar, Jacob Berenbeim, Andrzej L. Sobolewski, Mattanjah S. de Vries

    Indigo is a blue dye molecule that has been used since antiquity, although it is better known today for its use in blue jeans. Indigo has previously been shown to exhibit remarkable photostability due to fast excited state dynamics mediated by an excited state intramolecular proton transfer. Study of this process is complicated by the fact that the photophysics of indigo is very sensitive to the environment. In order to disentangle the intrinsic photodynamics of indigo from the effects contributed by the environment, we studied indigo in a molecular beam using resonance enhanced multiphoton ionization. We obtained excited state lifetimes of individual vibronic bands with pump-probe spectroscopy ranging from 60 ps to 24 ns. We have mapped a barrier to relaxation at about 700 cm-1, beyond which fast excited state dynamics dominate. Below this barrier two decay processes compete and mode-specific relaxation occurs with certain vibronic bands near the origin relaxing faster than others, or exhibiting different partitioning between the two relaxation channels. Computational studies at the ADC(2)/MP2/cc-pVDZ level indicate that two low-barrier reaction paths exist in the S1 state of indigo, one corresponding to proton transfer, the other to hydrogen transfer. In both cases the charge distribution changes drastically upon de-excitation. These data provide a sensitive probe of the potential energy landscape, responsible for the response to absorption of light. The results may help in understanding the photostability that preserves the blue color of indigo dyes.

    更新日期:2018-09-25
  • Dynamical Consequences of Time-Reversal Symmetry for Systems with Odd Number of Electrons: Conical Intersections, Semiclassical Dynamics, and Topology
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-24
    Ruixi Wang, Vladimir Y. Chernyak

    In this manuscript we identify the main differences between the effects of Kramers symmetry on the systems with even and odd number of electrons, the ways how the aforementioned symmetry affects the structure of the Conical Seams (CSs), and how it shows up in semiclassical propagation of nuclear wavepackets, crossing the CSs. We identify the topological invariants, associated with CSs, in three cases: even and odd number of electrons with time-reversal symmetry, as well as absence of the latter. We obtain asymptotically exact semiclassical analytical solutions for wavepackets scattered on a CS for all three cases, identify topological features in a non-trivial shape of the scattered wavepacket, and connect them to the topological invariants, associated with CSs. We argue that, due to robustness of topology, the non-trivial wavepacket structure is a topologically protected evidence of a wavepacket having passed through a CS, rather than a feature of a semiclassical approximation.

    更新日期:2018-09-25
  • Probing electron dynamics in the double photoionization process of two-valence electron systems with extreme UV and soft X-ray free-electron laser pulses
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-24
    Samira Barmaki, Marc-André Albert, Stéphane Laulan

    We numerically investigate the removal of the two outer electrons in the X = He, Li+, C4+, Be, B+ and Ne6+ targets by the absorption of a single photon of energy in the extreme UV/soft X-ray spectral region. Our theoretical method to describe the behavior of the electrons in the presence of the laser field is based on a spectral approach of configuration interaction type to solve the time-dependent Schrödinger equation. The probe of the electron dynamics in the different systems shows that the way the outer electrons will leave their parent X system is systematically dictated by the amount of excess photon energy available to them relative to the ionization potential of the corresponding X+ ion.

    更新日期:2018-09-25
  • Theoretical analysis of the drift and diffusion of charge carriers in thin layers of organic crystals
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-20
    D.V. Nikerov, N.A. Korolev, V.R. Nikitenko, A.P. Tyutnev

    The influence of diffusion on the current shape in the time-of-flight (TOF) experiment under conditions of the quasiequilibrium transport has been considered. An analytical expression for the transient current density has been obtained for the case of the reflecting front electrode. The expression has been found to be in a better agreement with the Monte-Carlo numerical modeling than the usual expression based on the standard convection–diffusion equation. We found an estimate of the minimum layer thickness for a flat plateau appearance on TOF current transients.

    更新日期:2018-09-20
  • Computational Study on the O- and Cl-Loss Dissociations of ClOO
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-19
    Qingyong Meng

    To study the O- and Cl-loss dissociations of the ClOO radical, we calculate, under Cs or C∞v symmetry, the O- and Cl-loss dissociation potential energy curves (PECs) from ten lower-lying states of ClOO at the multiconfigurational second-order perturbation theory (CASPT2) level. To further consider the nonadiabatic process, minimum-energy crossing point (MECP) between potential energy surfaces is optimized at the complete active space self-consistent-field (CASSCF) level. Since the spin-orbital coupling at located 22Π/14Σ+ MECP is calculated being zero, the nonadiabatic process in ClOO dissociations involved in this MECP are forbidden. Based on these results, we predict the O- and Cl-loss dissociation mechanisms of ClOO are direct since the excited states are unbounded. Moreover, we propose a new isomerization mechanism between OClO and ClOO, that is, OClO (X∼2B1) →OClO (A∼2A2) →ClOO (22A′′) →ClOO (X∼2A′′), in which less nonadiabatic processes are involved.

    更新日期:2018-09-20
  • DFT prediction of band gap in organic-inorganic metal halide perovskites: an exchange-correlation functional benchmark study
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-18
    Noemí Hernández-Haro, Joaquín Ortega-Castro, Yaroslav B. Martynov, Rashid G. Nazmitdinov, Antonio Frontera
    更新日期:2018-09-19
  • The dependence of hydrophobic interactions on solute size
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-18
    Q. Sun, X.W. Su, C.B. Cheng
    更新日期:2018-09-19
  • Modulation of electronic properties of monolayer InSe through strain and external electric field
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-18
    Doan Q. Khoa, Duy Trinh Nguyen, Chuong V. Nguyen, Vo T.T. Vi, Huynh V. Phuc, Le T.T. Phuong, Bui D. Hoi, Nguyen N. Hieu

    In this work, we consider systematically the influence of uniaxial strain and external electric field E on electronic properties of a monolayer InSe using ab-initio approach based on density functional theory. Our calculations indicate that the monolayer InSe has a medium indirect energy bandgap of 1.38 eV at equilibrium. The calculated results also demonstrate that we can adjust the bandgap of the monolayer InSe by strain engineering or electric field. The bandgap of the monolayer InSe changes dramatically when the uniaxial strain is applied. Especially, under the compressed uniaxial strain, an indirect–direct bandgap transition has been observed at certain elongations. Within the electric field magnitude E range from 0 to 5 V/nm, the calculated results show that the negative electric field changes the bandgap of the monolayer InSe up to 23% while the positive electric field effect on its bandgap is negligible.

    更新日期:2018-09-19
  • The Zero Point Position in Morse’s Potential and Accurate Prediction of Thermal Expansion in Metals
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-15
    Enrico Benassi

    The analytical expression for the matrix elements between Morse’s wavefunctions is shown. These results are computationally inexpensive and fast. The developed formulae show that the anharmonicity is responsible for a non-null displacement with respect to the equilibrium position at 0 K, that we call Zero Point Position. The theoretical model is implemented into the development of a simple atomic-level model for the estimation of temperature-dependent thermal expansion coefficients of bulk metals, which is presented in this study. This model provides an efficient and rapid way for evaluating material mechanic properties. Furthermore, a temperature-dependent modified Morse potential is also developed and validated. These models are analytical and are successfully tested on a series of metals.

    更新日期:2018-09-17
  • Excited States Dissociation Dynamics of Indole-x-Carboxaldehyde (x = 4, 5, 6, 7): Theoretical and Experimental Study
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-15
    Yuri A. Dyakov, Yu-Chieh Ho, Wen-Hsin Hsu, Chi-Kung Ni
    更新日期:2018-09-17
  • Signature of the geometric phase in the wave packet dynamics on hypersurfaces
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-15
    Hong-Guang Duan, Da-Long Qi, Zhen-Rong Sun, R.J. Dwayne Miller, Michael Thorwart

    We study the nonadiabatic dynamics of an electronic wave packet on two coupled potential energy surfaces. We focus on the difference between two configurations, the presence of a conical intersection (CI) and an avoided crossing (AC). We project the time-dependent dynamics onto the tuning and the coupling modes. For weak intersurface coupling, no significant difference appears. However, significant differences in the deactivation of the wave packet arise for increasing intersurface coupling. Most striking is a strong destructive interference of the two pathways of the wave packet which differ by a factor of π when moving around the CI. This yields to a vanishing of the wave packet in the CI configuration, which does not exist with an avoided crossing. By this, it is straightforward to identify the geometric phase in the wave packet dynamics and to use it to distinguish a CI from an AC configuration.

    更新日期:2018-09-17
  • Substituent effects on the nonadiabatic dynamics of ethylene: π-donors and π-acceptors
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-14
    Ryan J. MacDonell, Michael S. Schuurman

    The energetic and structural trends in the minimum energy conical intersections of a series of substituted ethylenes are explained by the degree to which the chemical substituents polarize electron density across the C=C double bond. The addition of a substituent that significantly polarizes the electron density also reduces the magnitude of the large-amplitude pyramidalization motions required to reach a conical intersection and can thus very effectively “direct” these motions to occur at a specific carbon atom. These observations are summarized via the construction of a reduced dimensionality representation of the relevant potential energy surfaces inspired by a previously reported 3-state model for biradical systems. On-the-fly nonadiabatic dynamics simulations reveal that this effect dictates the dominant excited state decay pathway for acrylonitrile (π-acceptor CN substituent) and vinylamine (π-donor NH2 substituent). The ab initio multiple spawning simulations show that population transfer to the ground electronic state for both molecules occurs primarily in the regions around the substituent-altered minimum energy conical intersections, demonstrating that chemical substitution may be used to selectively alter photochemical pathways.

    更新日期:2018-09-15
  • Theoretical Studies on 4H-Cyclopenta[2,1-b:3,4-b‘]dithiophene-based Windmill-shaped Nanogrids with Low Reorganization Energies
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-14
    Lei Yang, Jie Mao, Cheng-Zhu Yin, Xiang-Ping Wu, Yu-Yu Liu, Ling-Hai Xie, Xue-Qin Ran, Wei Huang
    更新日期:2018-09-15
  • Copper (II) Schiff base-graphene oxide composite as an efficient catalyst for Suzuki-Miyaura reaction
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-14
    Rasheeda M. Ansari, Badekai Ramachandra Bhat
    更新日期:2018-09-14
  • Influence of Temperature on the Swelling Pressure of Bentonite Clay
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-10
    Bukunmi Akinwunmi, Linlin Sun, Janne T. Hirvi, Seppo Kasa, Tapani A. Pakkanen
    更新日期:2018-09-11
  • A nonvolatile organic resistive switching memory based on lotus leaves
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-11
    Yiming Qi, Bai Sun, Guoqiang Fu, Tengteng Li, Shouhui Zhu, Liang Zheng, Shuangsuo Mao, Xiang Kan, Ming Lei, Yuanzheng Chen
    更新日期:2018-09-11
  • 更新日期:2018-09-07
  • Photoinduced hydrogen-transfer reactions in pyridine-water clusters: Insights from excited-state electronic-structure calculations
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-06
    Xiaojuan Pang, Johannes Ehrmaier, Xiuxiu Wu, Chenwei Jiang, Weiwei Xie, Andrzej L. Sobolewski, Wolfgang Domcke
    更新日期:2018-09-06
  • Achieving ultrafast topologically-protected vibrational energy transfer in a dimer chain
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-06
    Chang-Yu Hsieh, Pablo Carpio-Martinez, Gabriel Hanna

    Vibrational energy transfer through molecules plays a crucial role in many chemical and biological processes. Understanding the transfer rates and mechanisms may not only shed light on these processes, but may also lead to technological developments in the areas of quantum information processing and molecular electronics. Recently, it was shown that it is possible to induce robust long-range transfer of strongly correlated particles in a one-dimensional dimer chain model by tuning the chain’s topology. In the present work, we consider the effect of coupling this dimer chain to a chain of coupled harmonic oscillators on the energy transfer dynamics. This is accomplished by performing mixed quantum-classical dynamics simulations of the composite system, in which the dimer chain is treated quantum mechanically while the chain of coupled harmonic oscillators is treated classically. We investigate the energy transfer dynamics for a wide range of model parameters and disorders by monitoring the time-dependent population of each mode in the dimer chain. Interestingly, when the dimer chain is in its topologically non-trivial phase, we find that the population transfers from one end of the chain to the other (without passing through the intermediate sites) on a ∼100 fs timescale, in contrast to the ∼10 ps timescale observed in the original model. In addition, this transfer is found to be quite robust in the presence of weak disorder in the dimer chain. These results point to the possibility of achieving ultrafast, topologically-protected energy transfer in polymeric materials with appropriate molecular compositions and architectures.

    更新日期:2018-09-06
  • The Origin of Fluorescence in DNA Thio-Analogues
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-06
    Tolga N.V. Karsili, Mushir Thodika, Linh Nguyen, Spiridoula Matsika

    Fluorescent probes are vital molecular tools for DNA biognostics - often aiding in the detection of malignant tumors. Biomimetic nucleobase analogues are amongst the most widely used probes due to their versatility and biocompatibility. Thieno[3,4-d]pyrimidin-4-amine (TPA) and isothiazolo[4,3-d]pyrimidin-7-amine (iTPA) are two recently developed sulphur-containing heteroaromatic fluorescent nucleobase analogues. Their inherent structures give rise to superior biomimetic properties that ensure their optimal interaction with double-helix DNA. Using high-level electronic structure methods, we simulate the absorption and emission spectra in order to better understand the origins of the strong absorption and emission profiles observed experimentally. Radiationless decay pathways are also computed and compared with those of the canonical DNA nucleobases, in order to unravel the geometric and electronic properties that make the thio-analogues fluorescent.

    更新日期:2018-09-06
  • Molecular dynamics study of the thermal conductivity in nanofluids
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-04
    I. Topal, J. Servantie

    We evaluate the thermal conductivity of a model nanofluid at various volume fractions of nanoparticles with equilibrium (EMD) and non-equilibrium (NEMD) molecular dynamics simulations. The Green-Kubo formalism is used for the EMD simulations while a net heat flux is imposed on the system for the NEMD simulations. The nanoparticle-nanoparticle, fluid-fluid and fluid-nanoparticle interactions are all taken as Lennard-Jones potentials. An empirical parameter is added to the attractive part of the potential to control the hydrophilicity of the nanoparticles, hence controlling how well dispersed are the nanoparticles in the base fluid. The results show that the aggregation of the nanoparticles does not have a measurable effect on the conductivity of the nanofluid. Nanofluids with volume fractions of 2% and 3% show an enhanced conductivity with respect to the bulk fluid. Surprisingly, nanofluids with higher volume fractions did not show any enhancement of the conductivity.

    更新日期:2018-09-05
  • Two-phase interface-facilitated synthesis of graphene-like carbon nanosheets and their interfacial assembly behaviors
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-05
    Hongyi Gao, Junyong Wang, Mengyi Jia, Xiao Chen, Radoelizo S. Andriamitantsoa, Panpan Liu
    更新日期:2018-09-05
  • Analysis of the thermal fluctuations in inclusion complexes of genistein with β-cyclodextrin derivatives
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-05
    Valentina Venuti, Carmelo Corsaro, Rosanna Stancanelli, Alessandro Paciaroni, Vincenza Crupi, Silvana Tommasini, Cinzia A. Ventura, Domenico Majolino
    更新日期:2018-09-05
  • Effects of surface rates for the series reaction A → B → C on successive separated spherical sites
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-01
    William Strieder, Abby Samson, Salma Saddawi
    更新日期:2018-09-03
  • Effective quenching and excited-state relaxation of a Cu(I) photosensitizer addressed by time-resolved spectroscopy and TDDFT calculations
    Chem. Phys. (IF 1.707) Pub Date : 2018-09-01
    Aleksej Friedrich, Olga S. Bokareva, Shu-Ping Luo, Henrik Junge, Matthias Beller, Oliver Kühn, Stefan Lochbrunner

    Homogenous photocatalytic systems based on copper photosensitizers are promising candidates for noble metal free approaches in solar hydrogen generation. To improve their performance a detailed understanding of the individual steps is needed. Here, we study the interaction of a heteroleptic copper (I) photosensitizer with an iron catalyst by time-resolved spectroscopy and ab-initio calculations. The catalyst leads to rather efficient quenching of the 3MLCT state of the copper complex, with a bimolecular rate being about three times smaller than the collision rate. Using control experiments with methyl viologen an appearing absorption band is assigned to the oxidized copper complex demonstrating that electron transfer from the sensitizer to the iron catalyst occurs and the system reacts along an oxidative pathway. However, only about 30% of the quenching events result in an electron transfer while the other 70% experience deactivation indicating that the photocatalytic performance might suffer from geminate recombination.

    更新日期:2018-09-03
  • “Theoretical study of electronic properties and isotope effects in the UV absorption spectrum of disulfur”
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-31
    Karolis Sarka, Sebastian O. Danielache, Alexey Kondorskiy, Shinkoh Nanbu

    The electronic structures of triplet S2 ground and excited states are studied by ab initio molecular orbital and configuration interaction calculation. Potential energy curves correlated with S(3P)+S(3P) and S(3P)+S(1D) at the dissociation limit are evaluated, and electronic terms for a total of 11 states are assigned. Transition dipole moments, as a function of internuclear distance, are determined for two allowed transitions to B″3Πu and B3Σu- excited states. The total absorption cross-sections are computed to estimate isotope-fractionation constants, ∊, for four most common isotopologues: 32S32S, 32S33S, 32S34S, and 32S36S by quantum close-coupling (R-matrix) expansion approach and they are found to lie in a mostly opaque to competing absorbers spectral window. We suggest that the photochemistry and isotopic effects of S2 are of significant importance and provide data showing high sensitivity of mass-independent fractionation to excitation wavelength. Zero-point energy based constants ∊ZPE are estimated as well to compare with the obtained isotope effects and two modes for MIF are present in three-isotope plots; large isotopic effects were observed for both 36S and 33S with an excitation wavelength-dependent fluctuation.

    更新日期:2018-09-01
  • Utilization of ultra-light carbon foams for the purification of emulsified oil wastewater and their adsorption kinetics
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-31
    Shuang Yang, Fei Wang, Qingguo Tang, Pengfei Wang, Zishuai Xu, Jinsheng Liang
    更新日期:2018-08-31
  • Dissipaton dynamics theory versus quantum master equations
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-31
    Yao Wang, ZhiJun Pan, Hou-Dao Zhang, YiJing Yan

    In this review article we present first a comprehensive account on the recently developed the dissipaton–equation–of–motion (DEOM) theory. This is a statistical quasi-particle theory for open quantum systems. It treats not only the quantum dissipative systems of primary interest, but also the hybrid environment dynamics that could be experimentally measurable. On the basis of the exact and nonperturbative DEOM theory, we then revisit some commonly used quantum master equations (QMEs). Traditionally, QMEs are concerned with the reduced system dynamics only. We will elaborate the fact that one can extract the hybridization bath dynamics, even from the second–order QMEs that are actually one–dissipaton theories. Illustrations will be carried out on the Fano interference spectroscopies of a model dimer system, in both the strong and weak optical response regimes.

    更新日期:2018-08-31
  • The effect of large autoionization decay rates (resonance widths) on cold molecular cross-sections and the reflection phenomenon
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-31
    Anael Ben-Asher, Edvardas Narevicius, Nimrod Moiseyev

    Autoionization resonance states are characterized by a complex potential energy surfaces, where the imaginary part is proportional to the decay rate. Sharp changes in the autoionization decay rates, with respect to the reaction coordinates, introduce reflections. That is, when the autoionization decay rate is very small outside the interaction region and large within it, the reactants will be reflected away from the interaction region. Consequently, the reaction is expected to be suppressed. However, no reflections was observed in the collision of H2 with He in the 3P state [Nature Chemistry 7 (11) (2015) 921-926], for which the autoionization decay rate is very large in the interaction region and it is small elsewhere. In this paper, we theoretically investigate the reflection phenomenon within cold-chemistry collisions. Moreover, we present the conditions for which such reactions will not be suppressed due to reflections.

    更新日期:2018-08-31
  • Blue-Green-Black Phosphorene Allotropes Conversion: Energetically Easy and Potentially Promising
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-28
    Mohamed Maatallah, Abdellah Jarid

    Three allotropic forms of phosphorene (Blue, Green and Black) are studied from both structural and electronic points of view. P-P bonds orientation change from vertical to lateral directions is behind the change from Blue to Black forms via Green one. The energetic profile shows that this conversion could take place easily. The rippling mode of the phosphorene sheet is rationalized using the naturel bond orbital (NBO) analysis. We present the landforms of these sheets as a result of MOs interaction depending on the kind (σ, σ∗ and/or LP), on the mode (lateral or axial), and on the position (geminal, vicinal or remote) of these MOs leading to an electronic delocalization phenomenon called hyperconjugation. The conversion Blue-Green-Black phosphorenes is accompanied by a change of properties, for example, from natural band gap (Blue form) to a sizable and tunable one (Green and Black forms). This change would confer to phosphorene the ability to be involved in the electronics and optoelectronics manufacturing. The geometrical optimization and the hyperconjugative rationalization were undertaken at B3LYP/6-311+G(d,p) level of theory and NBO partitioning scheme respectively.

    更新日期:2018-08-29
  • 更新日期:2018-08-29
  • Stochastically correlated versus uncorrelated quantum-state diffusion dynamics in different electronic states: third-order polarizations and two-dimensional vibronic spectra
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-27
    Johannes Wehner, Volker Engel

    We regard a vibronic system where laser-excitation coherently couples two electronic states. The interaction with an environment, leading to vibrational relaxation, is treated within the quantum-state diffusion method. Two propagation schemes are compared which involve stochastically correlated dynamics in the two states on the one hand and uncorrelated dynamics on the other. Whereas expectation values of various observables are found to be insensitive to the propagation scheme, phase-sensitive quantities are not. This is illustrated regarding third-order time-dependent polarizations and two-dimensional vibronic spectra derived from them.

    更新日期:2018-08-28
  • 更新日期:2018-08-27
  • Exploring vibrational ladder climbing in vibronic coupling models: Toward experimental observation of a geometric phase signature of a conical intersection
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-25
    Hazem Daoud, Loic Joubert-Doriol, Artur F. Izmaylov, R.J. Dwayne Miller

    Conical intersections (CIs) have been widely studied using spectroscopic techniques. However, CIs have mainly been identified by rapid internal conversion transitions that take place after the photoexcitation. Such identifications cannot distinguish various types of intersections as well as to separate the actual intersection from an avoided crossing. In this paper, we investigate how ultrafast IR laser pulses can be utilized to stimulate nuclear dynamics revealing geometric phase features associated with CIs. We consider two low-dimensional nonadiabatic models to obtain optimal two- and three-pulse laser sequences for stimulating nuclear dynamics necessary for the CI identification. Our results provide insights on designing non-linear spectroscopic schemes for subsequent probes of the nuclear wavepackets by ultrafast electron diffraction techniques to unambiguously detect CIs in molecules.

    更新日期:2018-08-26
  • Influence of molecular shape on self-diffusion under severe confinement: A molecular dynamics study
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-24
    I. Dhiman, U.R. Shrestha, D. Bhowmik, D.R. Cole, S. Gautam

    We have investigated the effect of molecular shape and charge asymmetry on the translation dynamics of confined hydrocarbon molecules having different shapes but similar kinetic diameters, inside ZSM-5 pores using molecular dynamics simulations. The mean square displacement of propane, acetonitrile, acetaldehyde, and acetone in ZSM-5 exhibit two different regimes - ballistic and diffusive/sub-diffusive. All the molecules except propane exhibit sub-diffusive motion at time scales greater than 1 ps. The intermediate scattering functions reveal that there is a considerable rotational-translational coupling in the motion of all the molecules, due to the strong geometrical restriction imposed by ZSM-5. Overall the difference in shape and asymmetry in charge imposes severe restriction inside the ZSM-5 channels for all the molecules to different extents. Further, the behavior of molecules confined in ZSM-5 in the present study, quantified wherever possible, is compared to their behavior in bulk or in other porous media reported in literature.

    更新日期:2018-08-24
  • Molecular Analysis of Selective Gas Adsorption within Composites of Ionic Polyimides and Ionic Liquids as Gas Separation Membranes
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-23
    Asghar Abedini, Ellis Crabtree, Jason E. Bara, C. Heath Turner
    更新日期:2018-08-23
  • aPulse-shape effects in fifth-order multidimensional optical spectroscopy
    Chem. Phys. (IF 1.707) Pub Date : 2018-08-22
    Thanh Nhut Do, Lipeng Chen, Andrey K. Belyaev, Howe-Siang Tan, Maxim F. Gelin

    We study how the effects of finite pulse durations modify the fifth-order two-quantum two-dimensional (2Q-2D) and three-dimensional (3D) optical spectra. Instead of directly calculating the time domain polarization, the equivalent approach in frequency domain significantly simplifies the calculations and delivers exact expressions for the 2Q-2D and 3D spectra. Our results minimize the number of numerical integrations needed. We also derive simple analytical formulas for practically important situations when the laser pulses are short on the timescale of nuclear motion as well as short (or long) on the timescale of electronic dephasing. These formulas evaluate the measured spectra by multiplying the spectral response function by a factor depending on the spectral pulse envelopes.

    更新日期:2018-08-22
Some contents have been Reproduced with permission of the American Chemical Society.
Some contents have been Reproduced by permission of The Royal Society of Chemistry.
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