Chemical Physics Letters (v.496, #4-6)
Editorial Board (IFC).
Theory of multiexciton generation in semiconductor nanocrystals by Eran Rabani; Roi Baer (227-235).
Display Omitted► Unified theory of multiexciton generation in nanocrystals. ► Energy- and size-dependence of the efficiency of charge multiplication in nanocrystals. ► Multiexciton generation in CdSe, InAs, and silicon.We develop a generalized framework based on a Green’s function formalism to calculate the efficiency of multiexciton generation in nanocrystal quantum dots. The direct/indirect absorption and coherent/incoherent impact ionization mechanisms, often used to describe multiexciton generation in nanocrystals, are reviewed and rederived from the unified theory as certain approximations. In addition, two new limits are described systematically – the weak Coulomb coupling limit and the semi-wide band limit. We show that the description of multiexciton generation in nanocrystals can be described as incoherent process and we discuss the scaling of multiexciton generation with respect to the photon energy and nanocrystal size. Illustrations are given for three prototype systems: CdSe, InAs and silicon quantum dots.
Characterization and spectroscopic analysis of phenol–ethanol hydrogen bonded clusters by Rafael C. Barreto; Sylvio Canuto (236-242).
A theoretical characterization and spectroscopic properties of nine phenol–ethanol hydrogen bonded clusters. Influence on the electronic spectrum is also analyzed.Display Omitted► Some of the phenol–ethanol clusters are identified for the first time. ► A theoretical characterization is presented with analysis of the rotational, infrared and electronic spectra. ► They are analyzed as the precursor of the red shift in the electronic spectrum of phenol in liquid ethanol.Different hydrogen bonded clusters involving phenol and ethanol are studied theoretically using MP2/aug-cc-pVDZ. Nine different 1:1 clusters are obtained and analyzed according to their stability and spectroscopic properties. Different isomeric forms of ethanol are considered. Attention is also devoted to the spectral shift of the characteristic π → π∗ transition of phenol. Using TDHF, CIS, CIS(D) and TDB3LYP in aug-cc-pVDZ basis set, all results agree that a red shift is obtained when phenol is the hydrogen donor and a blue shift is obtained in the opposite case. These results are used to rationalize the red shift observed for phenol in liquid ethanol.
Electronic structure of ScN: Jet-cooled laser-induced fluorescence spectroscopy by S.G. Nakhate; Sheo Mukund (243-247).
Rotational structure of the (0, 0) D1–X 1Σ+ excitation band of jet-cooled ScN molecule.Display Omitted ► 1Σ+ symmetry for ground state of ScN molecule confirmed. ► Fundamental vibration in the ground state measured. ► Three new excited states with Ω = 1 observed. ► Fundamental vibrations and internuclear distances for new excited states measured. ► New excited states cannot be accounted for based on existing ab initio results.Jet-cooled spectra of ScN molecules were observed in the range 19 300–21 800 cm−1 using laser-induced fluorescence spectroscopy. The spectra showed nine vibronic bands belonging to three systems. Rotational analysis confirmed 1Σ+ symmetry for the ground state and also identified three new excited electronic states B1, C1, and D1, respectively, at 20150.3(1), 20184.4(1) and 21774.6(1) cm−1. The fundamental vibration in the ground state was measured to be 794.1(1) cm−1. The identity of the newly observed states cannot be corroborated using existing ab initio results and demand more rigorous calculations taking into account excited asymptotes, in particular Sc(3d14s2 2 D) + N(2 D).
Quantum reactive scattering calculations of H + F2 and Mu + F2 reactions on a new ab initio potential energy surface by Tomokazu Tanaka; Toshiyuki Takayanagi (248-253).
Quantum reactive scattering calculations for the H + F2 and Mu + F2 reactions were performed on a newly developed ab initio potential energy surface. A strongly curved Arrhenius plot of calculated rate constants for Mu + F2 due to tunneling was reproduced in the present theoretical calculations.Display Omitted►A global ab initio potential energy surface for the HFF system was constructed. ►Quantum scattering calculations for H + F2 and Mu + F2 reactions were performed. ►Arrhenius plot of calculated rate constants for Mu + F2 showed a curved behavior.A global potential energy surface of the H + F2 → HF + F reaction was developed at the MRCI/aug-cc-pVQZ ab initio electronic structure level. Time-independent quantum reactive scattering calculations were performed on the developed potential energy surface. Thermal rate constants for the H + F2 and Mu + F2 reactions were calculated from the J = 0 cumulative reaction probabilities and compared to available experimental data. A strongly curved Arrhenius plot observed in the Mu + F2 experiments was nearly reproduced by the present quantum dynamics calculations. The effect of F2 vibrational excitation on reactivity is also discussed.
Ion-pair photodissociations of benzyl chloride through inner-valence electron excitations by Shan Xi Tian; Yun-Feng Xu; Yong-Feng Wang; Qiang Feng; Liuli Chen; Jinda Sun; Fuyi Liu; Xiao-Bin Shan; Liusi Sheng (254-256).
Display Omitted► In this Letter, we report an experimental study of ion-pair photodissociation dynamics of benzyl chloride. ► The Cl− product efficiency spectrum in the photon energy of ca. 14.5–16 eV is recorded and tentatively assigned as the excitation transitions from the inner-valence orbitals to Rydberg states.The ion-pair anion efficiency spectrum of Cl− produced in photoexcitations of benzyl chloride is recorded and tentatively assigned as the transitions from the inner-valence molecular orbitals to Rydberg orbitals. Two series transitions 16a′, 6a″ → np (n = 6, 7, 8, 9, …) are proposed to couple strongly with the ion-pair dissociations in the photon energy range of ca. 14.5–16.0 eV.
The butane condensed matter conformational problem by Adrian C.J. Weber; Cornelis A. de Lange; W. Leo Meerts; E. Elliott Burnell (257-262).
Display Omitted► Effect of orientationally ordered condensed phase on conformational statistics. ► Analysis of highly complicated NMR spectra obtained from solutes in ordered fluids. ► Application of models for orientational order to help elucidate the conformational problem involved with flexible molecules.From the dipolar couplings of orientationally ordered n-butane obtained by NMR spectroscopy we have calculated conformer probabilities using the modified Chord (Cd) and Size-and-Shape (CI) models to estimate the conformational dependence of the order matrix. All calculation methods make use of Gaussian 03 structures for the gauche and trans conformers. Calculations were performed for both the Rotational Isomeric State (RIS) approximation, as well as a continuous gas-phase potential for the dihedral angle rotation. Conformational probability distribution functions for butane as a solute in the ordered liquid–crystal solvent are obtained.
Thermal conductivity and interfacial energies of solid Sn solution in the Sn–Ag–In ternary alloy by Yavuz Ocak; Sezen Aksöz; Necmettin Maraşlı; Kazım Keşlioğlu (263-269).
Display Omitted► Thermal conductivities of different compositions in the Sn–Ag–In ternary alloy have been measured. ► Solid–liquid and grain boundary energies have been determined for solid Sn solution in the Sn–Ag–In ternary alloy. ► The Gibbs–Thomson coefficient for Sn solution have been determined.The equilibrated grain boundary groove shapes of solid Sn solution in equilibrium with the Sn–Ag–In liquid have been observed from quenched sample. The Gibbs–Thomson coefficient, solid–liquid interfacial energy and grain boundary energy of solid Sn solution have been determined. The thermal conductivity values for solid Sn solution (Sn–2.1 at.%In) and eutectic solid (Sn–4.4 at.%Ag–2.1 at.%In) and the thermal conductivity ratio of eutectic liquid phase to eutectic solid for Sn–4.4 at.%Ag–2.1 at.%In alloy at the melting temperature have also been measured with a radial heat flow apparatus and Bridgman type growth apparatus, respectively.
Singlet–triplet spin–orbit coupling and crossing probability for the single-dimer cluster model of a Si(1 0 0) surface by Qing Zhu; Nicholas F. Materer (270-275).
Display Omitted► The minimum energy crossing point between singlet and triplet state is located near the higher-energy triplet state. ► The Si-dimer bond length increases as one progresses from the single state to the minimum energy crossing point and finally to the triplet state. ► The moderate spin–orbit coefficient (25 cm−1) at the minimum energy crossing point suggests a small but finite spin-crossing probability between singlet and triplet state at room temperature. ► Small geometry differences at the crossing points located by the different computational methods have insignificant influence on the spin–orbit coefficient. ► At higher temperatures, the population of the triplet Si-dimer is non-negligible, implying that the triplet set could play important roles in chemisorption and decomposition reactions on the Si(1 0 0) surface.The minimum energy crossing point of the singlet to triplet crossing for a single Si-dimer cluster has been determined using a variety of computational techniques. The crossing points located by the various computational methods were similar in structure and close to the triplet state in energy. At the crossing point, the spin–orbit coupling (SOC) coefficient was determined to be approximately 25 cm−1. Small geometry differences at the crossing points located by the different computational methods had insignificant influence on this value. Using this SOC, the Landau–Zener spin-crossing probability at room temperature was computed to be approximately 0.5%.
Investigation of ferromagnetism in Al-doped 4H–SiC by density functional theory by Lin Yu; Hao Jin; Donghong Liu; Ying Dai; Meng Guo; Baibiao Huang; Zhenkui Zhang (276-279).
The carbons around the silicon vacancy and the nearby Al dopant may be responsible for the ferromagnetism in Al-doped 4H–SiC.Display Omitted► We find out the possible theoretical origin of ferromagnetism in Al-doped 4H–SiC using first-principles methods and verify the experiments’ data. ► There is no any d electron in Al-doped 4H–SiC and p electrons dominion the ferromagnetism in this system. ► Silicon vacancy has high formation energy but it is one of the important factors of the ferromagnetism in Al-doped 4H–SiC.Ferromagnetism of Al-doped 4H–SiC is investigated by means of first-principles calculations. Our results show that Al dopant alone does not introduce any spin-polarization in the doped 4H–SiC, whereas the complex of substitution Al for Si together with a silicon vacancy can induce spin-polarization and local magnetic moment in Al-doped 4H–SiC. The interaction between the local moments results in the ferromagnetism order. The substitutional Al for Si atom introduces hole and mediates spin-polarizations resulting from silicon vacancy to form ferromagnetism in 4H–SiC.
Prediction of diamond-like, metallic boron structures by Yufeng Zhao; Qiang Xu; Lin J. Simpson; Anne C. Dillon (280-283).
Display Omitted► A generalized structure-decoration scheme was proposed based on current literatures on sp2 hybridized boron and applied to decoration of the sp3 backbone frameworks for prediction of new 3-dimensional boron crystals. ► The predicted boron crystals are metallic and have a much lower energy of formation than the known high-pressure boron phases. ► This study provides an explanation for the nonmetal–metal transition and the anomalous superconductivity of boron under high pressure. ► A mechanism that relaxes the intrinsic frustration of three-center bonding plays a unified role in both boron sheet and the predicted diamond-like boron.Diamond-like boron crystal structures are predicted employing a decoration scheme, in which the normal and hexagonal diamond frameworks are decorated with extra atoms across the basal plane. The predicted boron crystals can be viewed as isomorphs of αGa structured boron, but have a much higher density of states (DOS) near the Fermi levels. This study may provide a more plausible explanation for the nonmetal–metal transition and the anomalous superconductivity of boron under high pressure.
A density matrix based approach for studying excitons in organic crystals by Claudio Quarti; Daniele Fazzi; Matteo Tommasini (284-290).
Display Omitted► Transition density matrix approach to exciton description of molecular aggregates. ► Exciton structure calculation of p-Nitro-Aniline organic crystal. ► Exciton density of states and electronic absorption.A theoretical analysis of molecular excitons in crystalline p-Nitro-Aniline (PNA) is presented. The approach is general and can be straightforwardly extended to the calculation of the exciton structure of other molecular crystals or aggregates. Based on the evaluation of transition density matrices (TDM), the method allows to easily classify the excited states of interacting molecules on the basis of those of the constituent molecules. Exciton couplings of selected dimers within the PNA crystal have been evaluated and the exciton dispersion has been determined. The experimental absorption spectrum of PNA powders can be analysed in details based on the exciton density of states.
The interplay between structure and orbitals in the chemical bonding of graphite by Fabrizio Carbone (291-295).
Display Omitted► The electronic structure of graphite is calculated ab initio. We perform these calculations for different values of the lattice parameters, according to their evolution after light excitation reported by ultrafast electron diffraction. ► The changes in the electron energy loss spectrum of graphite due to the above-mentioned structural motions is simulated. ► These simulations are compared to the dynamical EELS spectrum experimentally measured in transmission through a graphite thin film. ► We show that the photoinduced structural motions modulate the electronic structure and give rise to the changes in the EELS spectra recently reported. ► This knowledge is used to simulate the effects of structural motions on the optical absorption spectra and we find that some long-term dynamics of the transient absorption signal are also due to photoinduced structural motions. ► We show how the charge density redistributes in the solid upon light excitation.Recently, the dynamics of atomic distances and orbital charge in graphite has been investigated by ultrafast electron diffraction, electron energy loss spectroscopy and transient optical absorption. A subtle interplay between structural motions and electronic degrees of freedom was found responsible for several peculiar behaviors like coherent phonon emission, photoinduced diamond formation, and graphene ablation. Here, we calculate ab initio the charge density of graphite, and observe its evolution during the above-mentioned structural distortions. The modifications of the electron energy loss and the optical spectra during c-axis compression and expansion are calculated and found in agreement with recent experiments.
Softening and activation of vibrational modes during the nonthermal fragmentation of C 60 by Carlos Rios; Felipe Valencia (296-300).
Display Omitted► Distinct softening for the vibrational modes with constant electronic temperature. ► Isothermal models may understimate the softening of some modes. ► Non thermal fragmentation proceeds through the activation of softened vibrational modes.The vibrational modes of a C 60 molecule irradiated with ultrafast laser pulses are studied, using a tight binding approach with variable occupations. It is shown that for the same level of electronic excitation, measured through the electronic temperature, each mode suffers a distinct softening. Excited trajectories below and above the damage threshold, are examined. It is shown that the bond breaking processes and the ulterior fragmentation might be described in terms of the activation of softened vibrational modes; and that the changes in frequency can be dramatically larger than those estimated with the isothermal model.
Three-dimensional phases-connectivity and strong magnetoelectric response of self-assembled feather-like CoFe2O4–BaTiO3 nanostructures by Yu Deng; Jianxin Zhou; Di Wu; Yulei Du; Mingsheng Zhang; Dunhui Wang; Huiqiang Yu; Shaolong Tang; Youwei Du (301-305).
The self-assembled feather-like CFO–BTO nanostructures and their magnetic and electric hysteresis loops.Display Omitted► Novel ME CFO–BTO nanostructures are synthesized by a cost-effective chemical route. ► A strong ME response has been achieved in the CFO–BTO nanostructures. ► The CFO–BTO exhibits good ferromagnetic and ferroelectric properties. ► A novel three-dimensional phases-connectivity promotes the ME effect. ► The formation mechanism of the nanostructures has been clarified.Magnetoelectric (ME) (CoFe2O4)0.3–(BaTiO3)0.7 (CFO–BTO) nanostructures have been synthesized by a combinative using of hydrothermal reaction and polymer-assisted deposition. The feather-like nanostructures have an average diameter of 250 nm and lengths up to 5 μm, with the single-crystal CFO nanopillars embedded in the BTO matrix. The CFO–BTO nanostructures exhibit good ferromagnetic and ferroelectric properties, as well as a large ME coefficient of 51.8 mV/cm Oe. A model has been proposed to explain the three-dimensional phases-connectivity of the nanostructures. And it is suggested that the novel type of phases-connectivity greatly promote the ME response.
Beryllium chains interacting with Graphene Nanoislands: From anti-ferromagnetic to ferromagnetic ground state by Stefano Evangelisti; Antonio Monari; Thierry Leininger; Gian Luigi Bendazzoli (306-309).
Display Omitted► Applications of ab initio methods to nano-systems. ► Stabilization of linear systems with Graphene Nanoisland. ► Presence of a significant van der Waals minimum. ► Singlet–triplet quasi-degeneracy of the linear Beryllium chains is onserved upon interaction with the nano-structure. ► Passage from an anti-ferromagnetic to a ferromagnetic ground state with the distance from the nano-structure.Electronic and magnetic properties of 1-D Beryllium chains interacting with Graphene nano-structures are studied at an ab initio level. In particular, linear Beryllium chains present significant dispersion interactions with Graphene Nanoislands. The magnetic properties of the 1-D Beryllium chains, are not destroyed by the interaction with the surface. However, the nature of the ground state depend strongly on the interaction: at long distance, the chain has an anti-ferromagnetic ground state; the ground state becomes ferromagnetic for distances from the surface shorter than about 3 Å. The behavior of the Beryllium system can shed light on the more general problem of the interaction of alkali-earth atoms in a 1-D arrangement and Graphene surfaces.
Chlorophyll a and pheophytin a as gas sensors of CO2 and O2 molecules by Rochele C.A. Bevilaqua; Ivana Zanella; Solange B. Fagan (310-315).
Display Omitted► Pheophytin as gas sensors. ► The chlorophyll a and pheophytin a as adsorbent of CO2 and O2 molecules. ► Spin polarization of the O2 molecule higher in the interaction with pheophytin a than with chlorophyll a. ► Charge transfers between pheophytin and CO2 and O2 molecules.The electronic and structural properties of porphyrin derivatives, such as chlorophyll a and pheophytin a, in pristine form and interacting with molecules of CO2 and O2 are investigated through ab initio calculations. Both chlorophyll a and pheophytin a can adsorb molecules of CO2 and O2 with binding energies around 0.2 eV indicating a physisorption regime. Modifications in the electronic properties of the resulting systems have been observed. These results are a consequence of the molecular levels of hybridization between the gases and the porphyrin molecules. Thus, these results open some possibilities to use those pigments as gas sensors.
Femtosecond pulsed laser induced synthesis of ultrafine Y2O3: Pr, Yb nanoparticles with improved upconversion efficiency by C.B. Zheng; Y.Q. Xia; F. Qin; Y. Yu; J.P. Miao; Z.G. Zhang; W.W. Cao (316-320).
Display Omitted► Low density foam-like nanostructure is prepared by fs pulsed laser irradiation. ► The mean particle diameter is about 10 nm. ► These nanoparticles are residue free. ► The upconversion emission characteristics is unique.Ultrafine Y2O3: Pr, Yb nanoparticles were produced by femtosecond pulsed laser ablation. Scanning and transmission electron microscope analyses indicated that these spherical particles have a diameter of about 10 nm with a narrow size distribution and no visible coalescence. These nanoparticles show much improved upconversion intensity compared to nanoparticles prepared by the sol–gel method and a new 510 nm emission band was observed. The time-resolved spectra indicated that the samples prepared by the laser method have longer decay time in spite of the smaller size, resulting from the exclusion of chemical residues, which lead to the enhancement of upconversion intensity.
Synthesis and electrical properties of a single walled carbon nanotube–borosilicate glass composite by A. Ghosh; S. Ghosh; S. Das; P.K. Das; D.D. Majumder; R. Banerjee (321-325).
Display Omitted► Single walled carbon nanotube–borosilicate glass composite has been fabricated by melt-quench technique. ► SWCNTs were found to be well dispersed inside the glass matrix. ► The electrical conductivity of the composite has been found to increase significantly due to incorporation of SWCNT in the glass host.Single walled carbon nanotube–borosilicate glass composite has been fabricated in a controlled atmosphere furnace by a melt-quench technique. Current–voltage characteristics were analyzed at room temperature and found to be non-ohmic in behavior. The temperature dependence of the current–voltage characteristics was ascertained and it was observed that the electrical conductivity of the composite increased substantially with temperature. Analysis by scanning and transmission electron microscopy clearly demonstrates that the carbon nanotubes are randomly distributed in the form of bundles throughout the glass. The charge conduction mechanism of the composite was found to be well explainable by the fluctuation induced tunneling (FIT) model.
Selective acoustic phonon mode excitation of multi-mode silver nanoprisms by Po-Tse Tai; Pyng Yu; Jane Huang; Jau Tang (326-329).
Display Omitted► Photo-induced acoustic phonons of the nanoprisms, which are breathing mode and totally symmetric mode, have been studied. ► We used two properly timed pump pulses to directly excite totally symmetric mode of the nanoprisms. ► Since the totally symmetric mode is mainly caused by impulsive electron stress, one could study electron dynamics from coherent acoustic phonon. We studied the relationship between excitation power and vibration amplitude, and the totally symmetric mode would disappear when excitation power is beyond a certain value.Nanoprisms are known to exhibit two major planar phonon modes in ultrafast experiments, namely, a stronger mode related to the bisector height and a weaker mode related to half of the edge length. In this work we demonstrated photoacoustic excitation of a specific acoustic phonon mode in silver nanoprisms using two properly timed pump pulses. Using this technique, we could selectively excite only the weak totally symmetric mode while suppressing the dominant breathing mode. Via direct observation of such a mode, which is hardly detectable directly with the conventional single pump pulse technique, we could elucidate the roles of hot electrons in photoinduced ultrafast structural dynamics in laser-heated nanoparticles.
Thermal luminescence spectra of lysine and phenylalanine in O2 measured with a Fourier-transform chemiluminescence spectrometer by Hiroshi Ishii; Chikahiro Satoh; Taishi Yamada; Taketo Karakisawa; Masahiko Sekine; Munetaka Nakata (330-334).
Display Omitted► A solid sample of Lys shows a thermal luminescence (TL) spectrum with a peak at ∼600 nm in O2 at 450 K but not in N2. ► No TL emission is observed from a solid sample of Lys·HCl salt in N2 or O2. ► A solid sample of phenylalanine shows no TL emission, while its dicyclohexylamine salt shows a TL spectrum with a peak at ∼660 nm. ► Interaction between the free NH2 group of amino acids and O2 molecules plays an important role for the TL emission.A thermal luminescence spectrum of solid lysine in O2 with an emission peak at ∼600 nm was measured at 450 K with a Fourier-transform chemiluminescence spectrometer. No emission bands were observed for lysine in N2, nor its monohydrochloride in O2 or N2, under the same experimental conditions. This observation led us to the conclusion that the intermolecular interaction between the free NH2 group on the side chain of lysine and O2 molecules plays an essential role in this thermal luminescence. This scheme was given support by the finding that the dicyclohexylamine salt of phenylalanine, which has a free NH2 group, but not phenylalanine itself, showed similar thermal luminescence in O2.
To the theory of Zeno chemical effect: The exactly solvable model by P.A. Purtov (335-338).
Phenomenological exponential model sometimes used in spin chemistry is substantiated with the exactly solvable quantum problem as an example. Thus it is shown that there is no complete analogy between the influence of quantum measurement and that of chemical reaction on the system evolution. It is noted that Zeno chemical effect, i.e., chemical process influence on singlet–triplet evolution was known in spin chemistry. However, some aspects of this phenomenon, for example, connection with the problem of quantum measurements have been insufficiently studied.Display Omitted► Spin chemistry. ► Analogy between the influence of quantum measurement and that of chemical reaction on the system evolution. ► Zeno chemical effect. ► The exactly solvable model.Phenomenological exponential model sometimes used in spin chemistry is substantiated with the exactly solvable quantum problem as an example. Thus it is shown that there is no complete analogy between the influence of quantum measurement and that of chemical reaction on the system evolution. It is noted that Zeno chemical effect, i.e., chemical process influence on singlet–triplet evolution was known in spin chemistry. However, some aspects of this phenomenon, for example, connection with the problem of quantum measurements have been insufficiently studied.
Variational solution for particle in a regular tetrahedron by Wai-Kee Li; S.M. Blinder (339-340).
An accurate variational calculation has been carried out for the totally symmetric ground state of a particle in a regular tetrahedron.Display Omitted► The Schrödinger equation for a particle in a regular tetrahedron cannot be solved in closed form. ► An accurate variational calculation has been made for the totally symmetric ground state. ► A semiempirical formula is conjectured for the ground states of a particle in a regular polyhedron.An accurate variational computation is carried out for a particle in a regular-tetrahedral box, a problem for which the Schrödinger equation cannot be solved in closed form. The ground-state energy is approximated by E 0 = 18.15 ℏ 2 / mV 2 / 3 , where V is the volume of the tetrahedron. A conjecture on the energies of particles in other regular polyhedra is proposed.
The multistate multimode vibronically coupled nuclear dynamics of monofluorobenzene radical cation using a parallelized TDDVR approach by Subhankar Sardar; Panchanan Puzari; Satrajit Adhikari (341-346).
Display Omitted► A multistate multimode molecular dynamics is performed for monofluorobenzene radical cation ( C 6 H 5 + ) using time-dependent discrete variable representation (TDDVR) methodology. ► Parallelized TDDVR approach reduces computational time more than an order of magnitude compare to its’ serial analogous calculation. ► TDDVR calculated photoelectron (PE), mass analyzed threshold ionization (MATI) and photoinduced Rydberg ionization (PIRI) spectra show good agreement with the profiles obtained from multiconfiguration time-dependent Hartree (MCTDH) approach.We have investigated the molecular dynamics of C 6 H 5 F + after excitation from the ground to different electronically excited states by using our parallelized Time Dependent Discrete Variable Representation method. Since the system consists of five electronic states with several conical intersections, a complex dynamical phenomena arises. TDDVR calculated population dynamics and various spectra, namely photoelectron, mass analyzed threshold ionization and photoinduced Rydberg ionization, etc. show good agreement with the results obtained by multiconfiguration time-dependent Hartree method as well as experimental findings. The parallelized TDDVR algorithm reduces the computation time drastically and appears to be a good compromise between accuracy and speed for such large molecular system.
LiH potential energy curves for ground and excited states with the free complement local Schrödinger equation method by Annika Bande; Hiroyuki Nakashima; Hiroshi Nakatsuji (347-350).
Display Omitted► Schrödinger accuracy potential curves of LiH. ► Both ground and excited states. ► Most accurate theoretical potential curve of LiH. ► Potential properties are also accurate.The two lowest singlet and triplet Σ+ potential energy curves of LiH were calculated using the free complement (FC) local Schrödinger equation (LSE) method. The overall potential curves and the properties calculated therefrom, like equilibrium bond length, dissociation energy, adiabatic and vertical excitation energies, zero point energy, vibrational spacings, etc., demonstrated the high accuracy of the FC LSE method for both the ground and excited states in comparison to the reference calculations and experiments.
End-point calculation of solvation free energy of amino-acid analogs by molecular theories of solution by Yasuhito Karino; Maxim V. Fedorov; Nobuyuki Matubayasi (351-355).
Display Omitted► Critical assessment of fast methods of the computation of the solvation free energy. ► Method of energy representation is useful in treating realistic systems. ► Integral equation theory achieves chemical accuracy in combination with informatics.The computational efficiency is improved for the solvation free energy when the calculation is restricted to the initial and final states of the solute insertion process (pure solvent and solution systems of interest). We explore the possibility of such ‘end-point’ calculations and assess the performance of several approximate free-energy functionals against benchmarks for amino-acid analogs in water. The performance is the best and the second, respectively, for the method of energy representation and the RISM (reference interaction site model)/partial-wave expansion supplemented by semi-empirical corrections for the excluded-volume and hydrogen-bonding effects, while the chemical accuracy is not achieved for the others.
Control of chemical reactions using external electric fields: The case of the LiNC ⇌ LiCN isomerization by G.E. Murgida; D.A. Wisniacki; P.I. Tamborenea; F. Borondo (356-361).
Display Omitted► A new method to control chemical reactions is proposed. ► The method is based on the use of varying electric fields, which makes the procedure simple and cheap, compared to other alternatives. ► The feasibility of the method is illustrated with and example; the LiNC = LiCN isomerization, which exhibit a rich dynamical behaviour.We explore the applicability to manipulate chemical reactions of a particularly simple method of quantum control that has been recently proposed in the literature . For this purpose we use a realistic model for the isomerization of LiNC.
Interaction energy of coupled permanent dipoles in oriented molecules by Michele Battezzati; Valerio Magnasco (362-364).
Display Omitted► This Letter is important in suggesting a method for the computation of one-sided averages of supermolecular dipole moments in presence of a static electric field not attainable through use of symmetrical procedures.The partition function of coupled molecular dipoles in a static electric field parallel to the supermolecular axis is evaluated by expanding the interaction energy function around the equilibrium position of minimum potential energy. The resulting expansion of the configurational integral is, as was proved by these same authors, an asymptotic representation in the limit of the strong interaction parameter a. This allows for the computation of one-sided averages of the supermolecular dipole moment not attainable through symmetrical procedures.
Author Index (365-370).