Chemical Physics Letters (v.530, #C)
Editorial Board (IFC).
Ultrafast Quantum Mechanics/Molecular Mechanics Monte Carlo simulations using generalized multipole polarizabilities by Tomasz Janowski; Krzysztof Wolinski; Peter Pulay (1-9).
Display Omitted► A very fast and accurate method is presented for QM/MM simulation of solutions. ► The quantum energy in the solvent electric field is determined from precalculated quantities. ► Precalculated generalized moments and polarizabilities allow fast quantum energy calculation. ► Our method is four orders of magnitude faster than the recalculation of the quantum energy. ► The method is virtually exact with polarizabilities included; without them, errors are ∼20 kJ/mol.A fast and accurate Quantum Mechanics/Molecular Mechanics method is described for thermodynamic simulation of solutes (or active sites in flexible molecules) in polar environments. The solute is described quantum mechanically and is held fixed during averaging over solvent configurations, which are described by Molecular Mechanics. Quantum calculations during simulation are replaced by the evaluation of the response of the solute to the long range electric field of the solvent, using precalculated generalized electric moments and polarizabilities. This results in huge decrease of computational time without affecting the accuracy of the QM/MM results. Implementation in a Monte Carlo program accelerated the simulations of guanine and the phenylalanine dipeptide in TIP3P water by over four orders of magnitude. Polarizability is essential for accuracy. Its inclusion decreases the average signed energy error and its standard deviation from 5.69 to 0.003 and 1.22 to 0.013 kcal/mol, respectively, for the dipeptide. Hyperpolarizability contributions are insignificant.
Infrared spectroscopy of V2+(H2O) complexes by B. Bandyopadhyay; M.A. Duncan (10-15).
The infrared photodissociation spectrum of V2+(H2O) tagged with four argon atoms. The vibrations are strongly red shifted from those of the isolated water molecule.Display Omitted► Vanadium cation complexes with water are produced in a molecular beam by laser vaporization. ► Ions are mass-selected and studied with IR photodissociation spectroscopy. ► O–H stretching frequencies are measured for V(H2O)Ar n m + cations for n = 1–7 and m = 1,2. ► Red-shifted O–H stretching frequencies are compared for complexes as a function of charge. ► The coordination of V2+ is filled with one water and five argon atoms.Doubly charged vanadium–water complexes are produced by laser vaporization in a pulsed supersonic expansion. Size-selected ions are studied with infrared photodissociation spectroscopy in the O–H stretch region using argon complex predissociation. Density functional theory calculations provide structures and vibrational spectra of these ions. The O–H stretches of V2+(H2O) appear at lower frequencies than those of the free water molecule or V+(H2O). The symmetric stretch is more intense than the asymmetric stretch in both V+(H2O) and V2+(H2O) complexes. Spectra of V2+(H2O)Ar n (n = 2–7) show that the coordination of the V2+ is filled with six ligands, i.e. one water and five argon atoms.
Analysis of the A ∼ – X ∼ electronic transition of the 2,1-hydroxypropylperoxy radical using cavity ringdown spectroscopy by Neal D. Kline; Terry A. Miller (16-24).
Display Omitted► Organic peroxy radicals are important reactive chemical intermediates in tropospheric oxidation. ► The NIR electronic spectrum of 2,1-hydroxypropylperoxy radical is observed. ► The origin and vibrational bands of the three most stable conformers are observed and assigned.The near infrared A ∼ – X ∼ electronic absorption spectrum of the 2,1-hydroxypropyl peroxy radical (2,1-HPP) has been recorded at room temperature by cavity ringdown spectroscopy. Twenty-five conformers of 2,1-HPP are predicted to exist as minima on the potential energy surface calculated via either ab initio or density functional theory. However, the experimental spectrum is explained in terms of the origin bands and vibrational structure of the three conformers predicted to be most stable. In addition to the OO stretch and COO bend bands typically observed in the A ∼ – X ∼ spectra of peroxy radicals, we attribute some observed bands to low-frequency fundamentals corresponding to the OOCC bending of 2,1-HPP. This assignment is supported by both Franck–Condon simulations and experiments on jet-cooled radicals.
Influence of solvation on the indole photophysics: Ultrafast dynamics of indole–water clusters by A. Peralta Conde; V. Ovejas; R. Montero; F. Castaño; A. Longarte (25-30).
Display Omitted► We studied the influence of the solvation on the dynamics of indole–water clusters. ► A time dependent study with femtosecond resolution of the dynamics is presented. ► The data permit the identification of the relaxation pathway to the ground state. ► A view of the water influence different from existing results is presented.The influence of water solvation on the photophysics of the indole chromophore has been investigated by revisiting the ultrafast relaxation of indole–water clusters. The dynamics after excitation in the 284–234 nm energy range has been tracked by time delayed ionization with a 1305 nm probe. The results collected in the indole– ( H 2 O ) 1 + mass channel, which were ascribed mainly to the indole– ( H 2 O ) 2 + cluster fragmented by dissociative ionization, reflect a dynamical behavior analogous to that observed for the isolated indole molecule. The two femtosecond time constants observed in the transients were assigned to the coupling between the L a and L b π π ∗ surfaces, and to the system evolution along the dissociative π σ ∗ state.
Observation of the linear C2H2–N2 van der Waals complex in the 2CH range using CW-CRDS by K. Didriche; C. Lauzin; T. Földes (31-34).
Display Omitted► CRDS spectrum of C2H2–N2 was recorded around the 2CH acetylene band. ► Twenty lines are assigned thanks to combination differences. ► Effective rotational constants and the band origin of the upper state are determined. ► Lifetime of the upper state is retrieved.CW-cavity ring down spectroscopy was used to record the spectrum of 12C2H2–N2 in a free jet expansion around the 2CH acetylene band. Twenty lines were assigned thanks to combination differences, which were combined with literature values leading to the retrieval of ground state rotational constants consistent for a broader set of J″. Effective rotational constants, the band origin and the estimation of the lifetime of the perturbed upper state are determined.
Studies of femtosecond time-resolved photoelectron spectroscopy of Au 3 - (H2O) m clusters: Alteration of cluster relaxation dynamics of metal clusters by water molecules by Christian Braun; Sebastian Proch; Hyun Ook Seo; Young Dok Kim; Gerd Ganteför (35-38).
Display Omitted► Relaxation dynamics of optically excited states of Au 3 - and Au 3 - (H2O) m were studied. ► One water molecule adsorbed on Au 3 - opened new photo-dissociation channels. ► More than one water molecules on Au 3 - inhibited photo-dissociation. ► Photochemistry is controlled by adjusting the number of adsorbed water molecules.Relaxation dynamics of optically excited states of Au 3 - and Au 3 - (H2O) m were studied via femtosecond time-resolved photoelectron spectroscopy (fsTRPES). Au 3 - exhibits photo-dissociation into either ( Au 2 - + Au1) or (Au2 + Au 1 - ) with a time constant of 1.6 ns. One water molecule adsorbed on Au 3 - opened new photo-induced dissociation channel with a much shorter time constant. More than one water molecule on Au 3 - inhibited photo-dissociation, most likely as a result of facile dissipation of excess energy of optically excited states by nuclear motions of clusters. The photochemical pathway can be controlled by adjusting the number of water molecules interacting with the ionic species.
Theoretical study of conjugated polyelectrolyte electron injection layers: Effects of counterions, charged groups and charge reversal by Huyen Thi Nguyen; Thuc-Quyen Nguyen; Minh Tho Nguyen (39-44).
Display Omitted► In conjugated polyelectrolytes (CPEs), electron and hole injections vary the planarity of the monomers. ► Their band gaps are invariant for monomers bearing the same backbone. ► CPEs could be potential candidates for electron-transport materials.The molecular structures, electronic and charge-transport properties of three conjugated polyelectrolytes (CPEs) including PFPhCO2Na, PFPhSO3Na, and PFPhBIm4 are studied using the density functional theory with B3LYP functional. The charge injection and charge transport properties are investigated through the ionization energies, electron affinities, lowest allowed excitation energies, reorganization energies and electron transfer integrals. The electron/hole injections have great effect on the planarity of cationic/anionic CPEs. The band gaps of the CPEs do not vary significantly with the charged groups and counterions. Charge-transport properties show that the PFPhSO3Na and PFPhBIm4 are good candidates for electron-transport materials.
Photophysics of Fe(III)–tartrate and Fe(III)–citrate complexes in aqueous solutions by Ivan P. Pozdnyakov; Alexander V. Kolomeets; Victor F. Plyusnin; Alexey A. Melnikov; Victor O. Kompanets; Sergey V. Chekalin; Nikolai Tkachenko; Helge Lemmetyinen (45-48).
Display Omitted► Fe(III) complexes with citric and tartaric acids were investigated by ultrafast spectroscopy. ► Biexponential decay of transient absorbance was observed. ► Lifetimes and spectral properties of the excited states of the Fe(III) complexes were determined. ► Possible mechanism of the excited states decay were proposed and discussed.Femtosecond pump–probe spectroscopy was used to determine the photophysical processes of Fe(III) complexes with citric and tartaric acids ([Fe(Cit)] and [Fe(tart)]+) in aqueous solutions. The excitation of the complexes in the charge transfer bands is followed by formation of an intermediate absorbance decaying with two characteristic times. The shorter time constant (0.2, 0.4 ps) is ascribed to vibrational cooling and solvent relaxation of Frank–Condon excited state of corresponding complex and the second time constant (1.4, 40 ps) is assigned to superposition of internal conversion to the ground state and formation of the long-lived Fe(II) radical complex. The competition of these processes determines the quantum yield of photolysis of Fe(III)–carboxylates.
Oximato-bridged light-lanthanide Ln4Cu complexes showing ferromagnetic Ln–Cu exchange coupling by Kei Fujiwara; Atsushi Okazawa; Norimichi Kojima; Go Tanaka; Shunsuke Yoshii; Hiroyuki Nojiri; Takayuki Ishida (49-54).
Display Omitted► Exchange couplings were evaluated by high-frequency EPR and magnetization techniques. ► This method can be broadly applied to 3d–4f heterometallic complexes. ► The coupling is ferromagnetic for all of the light lanthanide Ln4Cu compounds. ► A chemical trend of the coupling parameter is found in the order of the periodic table.Heterometallic pentanuclear coordination compounds [Ln3+ 4Cu2+] involving light lanthanide ions, Ce, Pr, Nd, Sm, and Eu, were synthesized and structurally characterized. The exchange interactions between the Ln and Cu ions were evaluated by high-frequency electron paramagnetic resonance and magnetization studies, clarifying the presence of ferromagnetic exchange couplings in Nd–Cu (J Nd–Cu/k B = +0.30(6) K) and Sm–Cu (J Sm–Cu/k B = +2.08(3) K), very small couplings in Ce–Cu and Pr–Cu, and the absence in Eu–Cu. A significant chemical trend is found in the order of the atomic number.
Diffusion in confinement as a microscopic relaxation mechanism in glass-forming liquids by Eugene Mamontov (55-60).
Display Omitted► Glass-forming and non glass-forming liquids are studied using quasielastic scattering. ► Glass-formers exhibit two separate relaxation components, non glass-former only one. ► The faster of the two components corresponds to the β-relaxation process. ► The β-relaxation can be described as a diffusion process in confined space (cage).Using quasielastic neutron scattering, we compare dynamics in single-element liquids, glass-forming selenium and non glass-forming gallium. There is a single jump-diffusion process in gallium, whereas in selenium there is also a faster, spatially localized process. The fast and slow processes describe β- and α-relaxation, respectively. We then analyze an archetypical glass-former, glycerol, to show that the two-component fit, with β- and α-relaxations explicitly separated, yields the correct value for the translational diffusion coefficient and provides information on the spatial localization of the β-relaxation that is not experimentally accessible otherwise.
Self-diffusion coefficient of lithium in molten xLi2O–(1 − x)B2O3 system using high-temperature PFG NMR by Takahiro Ohkubo; Mallory Gobet; Vincent Sarou-Kanian; Catherine Bessada; Muneharu Nozawa; Yasuhiko Iwadate (61-63).
Display Omitted► We examined lithium diffusion in Li 2 O – ( 1 - x ) B 2 O 3 melts by high-temperature PFG NMR. ► Activation energy, E a , were compared with viscosity, density and MD simulations. ► E a had the minimum value at x = 0.4, which was the same as density and BO4 fraction. ► We concluded E a depends on the depolymerization network and Coulomb interaction.Lithium diffusion was measured in xLi2O–(1 − x)B2O3 melts as a function of temperature and composition by high-temperature pulsed field gradient NMR. The 7Li self-diffusion coefficients were found to increase with increasing x when compared at the same temperature. It was of much interest that E a in the molten xLi2O – (1 − x)B2O3 system decreased monotonously with increasing Li2O content up to x = 0.4 and then increased at x = 0.45 and 0.5.
The B3LYP and BMK studies of CO adsorption on Pt(1 1 1): An insight through the chemical bonding analysis by Yu-Wei Huang; Shyi-Long Lee (64-70).
The geometries of CO adsorption on the Pt nanocluster.Display Omitted► The chemical bonding analysis of CO on Pt by using B3LYP and BMK method. ► The π interaction is reduced for BMK method. ► The σ-repulsion is reduced for the CO adsorption on top site for BMK method. ► The σ-repulsion is enhanced for CO adsorption on fcc and hcp sites for BMK method.The chemical bonding analysis was adopted to investigate the adsorption behavior of CO on Pt nanoclusters by using B3LYP and BMK. The analysis shows for BMK the dominating π-attraction is reduced and the minor π repulsion is enhanced no matter in which site the CO adsorbed, and thus the π interaction is reduced. In addition, the σ-repulsion is reduced for the CO adsorption on top site but enhanced for CO adsorption on fcc and hcp sites for BMK method. Our results show some insight into the CO/Pt(1 1 1) puzzle.
Structure of boron clusters revisited, B n with n = 14–20 by Truong Ba Tai; Nguyen Minh Tam; Minh Tho Nguyen (71-76).
Display Omitted► The B n clusters with n = 14–19 are planar structures. ► In disagreement with a recent report by Boustani et al., we find that the B19 cluster is planar. ► The transition between 2D and 3D structure occurs at the B20 that is a tubular form with highly aromatic feature. ► All neutral B n clusters have aromatic character.We reinvestigate the structures of neutral boron clusters B n , with n = 14–20. G3B3 calculations confirm that a transition between 2D and 3D shape occurs at B20, which has a tubular form. In disagreement with Boustani et al. (Phys. Rev. B, 83 (2011) 193405), we find a planar B19 cluster. Standard heats of formation are obtained and used to evaluate the clusters stability. The average binding energy tends to increase with increasing size toward a limit. Higher stability is found B14, B16, B18 and B20. All B n have negative NICS-values. The bonding nature and electron delocalization of B20 are re-examined using CMO and LOL.
Acceleration effect of adsorbed thiocyanate ions on electrodeposition of CuSCN, causing spontaneous electrochemical oscillation by Kazuhide Kamiya; Kazuhito Hashimoto; Shuji Nakanishi (77-80).
Display Omitted► Adsorbed SCN− ions exhibit acceleration effect of Cu(II) electrochemical reduction. ► Potential oscillation was induced by the acceleration effect of adsorbed SCN−. ► CuSCN and Cu are alternatively deposited in synchronization with the oscillation.It is shown that thiocyanate ions (SCN−) adsorbed on an electrode surface accelerate electrochemical reduction of Cu(II), resulting in the formation of CuSCN. The acceleration effect of adsorbed SCN− ions was proved by electrochemical impedance analysis and X-ray analyses of the resultant deposits. Importantly, spontaneous potential oscillation was observed during the Cu(II) reduction only in the presence of SCN−, further evidenced the acceleration effect of the adsorbed SCN−.
Monte Carlo simulation of carbon nanotube nucleation and growth using nonlinear dynamic predictions by Changqing Cheng; Satish T.S. Bukkapatnam; Lionel M. Raff; Martin Hagan; Ranga Komanduri (81-85).
Display Omitted► One of the longest CNTs (194 nm) from simulations. ► Simulation time reduced from about from 3–4 weeks to 2–5 days. ► CNT growth found to exhibit distinct nonlinear and nonstationary dynamics. ► Generic growth prediction approach to accelerate nanosynthesis simulations. ► Accurately captures and explains trends observed in physical experiments.The computation time for Monte Carlo (MC) simulation of a nanostructure growth process was shown to be reduced by an order of magnitude compared to conventional atomistic and meso-scale models through the prediction of the structure evolution ahead of every growth step. This approach used to grow of one of the longest (∼194 nm) reported carbon nanotubes (CNTs) from atomistic simulations. The key to the approach is the finding from simulation experiments that the CNT synthesis process exhibits nonlinear and recurring near-stationary dynamics.
Quantum interference through gated single-molecule junctions by Daniel A. Lovey; Rodolfo H. Romero (86-92).
Display Omitted► We discuss properties of the transmission function of single molecule junctions. ► Analysis of transmission antiresonances from Hückel molecular orbitals. ► Effect of application of gate potentials on aromatic molecules. ► Discussion of interplay between gate position and topology of connections.We discuss the general form of the transmission spectrum through a molecular junction in terms of the Green function of the isolated molecule. By introducing a tight binding method, we are able to translate the Green function properties into practical graphical rules for assessing beforehand the possible existence of antiresonances in an energy range for a given choice of connecting sites. The analysis is exemplified with a benzene molecule under a hypothetical local gate, which allows one to continuously tune the on-site energy of single atoms, for various connection topologies and gate positions.
Fabrication and characterization of aluminum nanostructures and nanoparticles obtained using femtosecond ablation technique by G. Krishna Podagatlapalli; Syed Hamad; S. Sreedhar; Surya P. Tewari; S. Venugopal Rao (93-97).
Characterization of Al nanoparticles obtained using femtosecond ablation. (a) Distribution histogram in colloidal CCl4 solution, (b) UV–Vis extinction spectra of the prepared colloidal solution, (c) Open aperture Z-scan curves obtained for colloidal CCl4 at three different intensities in increasing fashion (from green to red) in picosecond regime. SEM image of Al NPs in CCl4 is shown in the central figure.Display Omitted► We generated well dispersed Al nanoparticles with less oxide cladding through fs laser ablation. ► We observed micro- and nano-structure formation on the substrate with different focusing conditions. ► We could explain effect of polarity of the liquid medium on the size of nanoparticles formed. ► Nonlinear optical properties of the colloidal solutions of nanoparticles were carried out.In this communication we report the fabrication of nanoparticles (NPs) and nanostructures through the interaction of ultrashort laser pulses (∼40 fs) with bulk aluminum immersed in chloroform and carbon tetrachloride. The size distribution and surface morphology of substrates were investigated using scanning electron microscope images. Depending on the focal position we observed sub-micron structures and nano-ripples on the irradiated surface. Picosecond nonlinear optical studies of the prepared NPs colloidal solutions using open aperture Z-scan technique demonstrated complex behavior of switching from saturable absorption to reverse saturable absorption (RSA) at lower peak intensities to pure RSA at higher peak intensities.
Thermoluminescence in heavily F-doped of SnO2 nanocrystals by Vinod Kumar; R. Nagarajan (98-101).
Display Omitted► Thermoluminescence evolves in heavily F-doped semiconducting SnO2 nanocrystals. ► This is attributed to the creation of F-centers in the system. ► Analysis of the glow curves yielded a major trap of activation energy 1 eV. ► After UV irradiation for few minutes, generation of deeper traps occurred in SnO2:F.Without external irradiation, the heavily fluorine doped SnO2 nanocrystals show a broad glow curve at 454 K in the thermoluminescence spectrum. On irradiation with UV light, the glow curve of SnO2:F resolves in to two, one centred at 440 K and the other at 520 K. The glow curves, under different heating rates, before and after irradiation with UV light are analyzed by the Glow Curve Deconvolution procedure and peak shape methods. A major trap with activation energy of 1 eV coupled with high frequency factor of order of 1010 s−1 suggests it to be a potential direct contact temperature sensor.
Mode damping rates in a protein chromophore by David M. Leitner (102-106).
Display Omitted► Bottlenecks to vibrational relaxation in protein chromophores identified. ► Bottlenecks to energy flow give rise to underdamped low-frequency oscillations. ► Damping rates of protein modes are shown to be independent of protein size. ► Size of molecule where bottlenecks to energy flow appear is determined.A variety of optical studies reveal coherent low-frequency oscillations during photochemical reactions in proteins. We recently argued [New J. Phys. 12, Art. No. 085004 (2010)] that the vibrational eigenstates of an isolated chromophore may be localized, which can give rise to long-lived low-frequency vibrational modes when the chromophore is embedded in a protein. Here we show that, even if vibrational eigenstates are not localized, bottlenecks to vibrational energy flow that are absent in much larger molecules give rise to slow damping of low-frequency modes in many protein chromophores. Examples including rhodopsin, photoactive yellow protein and green fluorescent protein are discussed.
A relative Lempel–Ziv complexity: Application to comparing biological sequences by Liwei Liu; Dongbo Li; Fenglan Bai (107-112).
Display Omitted► The main advantage is that this method can extract repeated patterns from biological sequence. ► The time complexity of this algorithm is O(l(Q) × l(R)). ► We use this method to build phylogenetic tree. The result demonstrate that our method is powerful and efficient.One of the main tasks in biological sequence analysis is biological sequence comparison. Numerous efficient methods have been developed for sequence comparison. Traditional sequence comparison is based on sequence alignment. In this report, we propose a novel alignment-free method based on the relative Lempel–Ziv complexity to compare biological sequences. The vertebrate transferring genomes and the spike protein sequences are prepared and tested to evaluate the validity of the method. We use this method to build phylogenetic tree of two groups of the sequences. The result demonstrates that our method is powerful and efficient.
Orientation of a bacteriorhodopsin thin film deposited by dip coating technique and its chiral SHG as studied by SHG interference technique by Toshiki Yamada; Yoshihiro Haruyama; Katsuyuki Kasai; Toshifumi Terui; Shukichi Tanaka; Takahiro Kaji; Hiroshi Kikuchi; Akira Otomo (113-119).
Abundant information by observation SHG interference by using two SH chiral active films.Display Omitted► bR thin films prepared by a simple dip coating have a polar orientation with C∞. ► The interference fringes in p–p and s–p have opposite phase with that in p–s. ► Enhanced or restricted chiral SHG was observed at specific incident angles. ► Abundant information can be obtained by observing SHG interference.We show that by observing SHG interference bR thin films prepared by a simple dip coating technique have a polar orientation with C∞ symmetry. The SHG interference measurements were performed under various input and output polarization combinations at different incident angles or under the rotation of the quarter-wave retardation plate at specific incident angles. The interference patterns provide us with insight into the characteristics of non-vanishing nonlinear optical coefficients including chiral components. Abundant information can be obtained by observing SHG interference by using two chiral SH active films.
Composite pulses for efficient excitation of half-integer quadrupolar nuclei in NMR of static and spinning solid samples by Diego Carnevale; Geoffrey Bodenhausen (120-125).
Display Omitted► Excitation of the central transition of half-integer quadrupolar nuclei in solid state NMR. ► New composite pulse enhances the central transition by minimizing the creation of satellite single-quantum and multiple-quantum coherences. ► The method is efficient under both static and spinning conditions.Composite pulses of the type ( τ p ) x ( 2 τ p ) - x ( 3 τ p ) x allow one to excite the central transition of nuclei with half-integer spin with enhanced efficiency compared to a simple ( τ p sp ) x pulse. The method has been tested on solid samples containing sodium-23 (I = 3/2), aluminium-27 (I = 5/2) and scandium-45 (I = 7/2) under both static and magic-angle spinning conditions. Numerical simulations for I = 3/2 indicate that the enhancement is due to a more efficient conversion of Zeeman population differences associated with the satellite transitions to the central transition.
Solid-state circularly polarized luminescence measurements: Theoretical analysis by Takunori Harada; Reiko Kuroda; Hiroshi Moriyama (126-131).
Display Omitted► CPL signal was intrinsically influenced by the residual birefringence. ► An analytical method for obtaining artifact-free CPL spectra was newly developed. ► An analytical method is based on Stokes–Mueller matrix method. ► The procedure for true CPL measurements could eliminate artifact signals.Because a circularly polarized luminescence (CPL) spectrophotometer is a polarization-modulation instrument, artifacts resulting from optical anisotropies that are unique to the solid state necessarily accompany CPL signals. A set of procedures for obtaining the true CPL signal has been derived based on the Stokes–Mueller matrix method. Experiments on chiral fluorophore single crystals of benzil with larger and smaller optical anisotropies have shown that our method can eliminate parasitic artifacts to obtain the true CPL signal, even in cases where optical anisotropies are substantial.
Constrained self-consistent field method revisited toward theoretical designs of functional materials under external field by Yuya Yamagata; Yutaka Imamura; Hiromi Nakai (132-136).
Display Omitted► We revisited constrained density functional theory in terms of material designs. ► We examined the physical meaning of a Lagrange multiplier in CSCF. ► Numerical stability of CSCF was examined for the benzene molecule. ► The activation energies and critical electric fields were efficiently estimated.This Letter explores the potential utility of the constrained self-consistent field (CSCF) method as an efficient methodology for estimating the external fields that reproduce desired physical quantities. Using the fact that a Lagrange multiplier introduced in CSCF corresponds to an external field (perturbation), numerical assessments of CSCF were carried out on the benzene molecule. The activation energies and critical electric fields that reverse the polarizations of the ferroelectric material tetrathiafulvalene-p-chloranil (TTF-CA) were efficiently estimated. The numerical assessments demonstrate the potential applicability of CSCF for the practical designs of materials possessing certain desired physical quantities induced by external fields.
The role of Ce(III) in BZ oscillating reactions by Paulo A. Nogueira; Hamilton Varela; Roberto B. Faria (137-139).
Display Omitted► No oscillations are observed in a CSTR on the bromate–oxalic acid–acetone–Ce(IV) system. ► Ce(III) is the only catalyst necessary to produce oscillations on this system. ► When Ce(IV) is used, the induction period is a time necessary to convert Ce(III) to Ce(IV).Herein we present results on the oscillatory dynamics in the bromate–oxalic acid–acetone–Ce(III)/Ce(IV) system in batch and also in a CSTR. We show that Ce(III) is the necessary reactant to allow the emergence of oscillations. In batch, oscillations occur with Ce(III) and also with Ce(IV), but no induction period is observed with Ce(III). In a CSTR, no oscillations were found using a freshly prepared Ce(IV), but only when the cerium-containing solution was aged, allowing partial conversion of Ce(IV) to Ce(III) by reaction with acetone.
Quantum master equations for non-linear optical response of molecular systems by Tomáš Mančal; František Šanda (140-144).
Display Omitted► We consider non-linear response functions for a simple two-level molecular system. ► It is shown that it cannot be constructed using a single reduced density matrix master equation. ► A set of master equations is derived which together reproduce the two-level response function. ► Parametric projection operators are introduced to derive proper equations in general cases.Generalized master equations valid for the third order response of an optically driven multi-level electronic system are derived within Zwanzig projection formalism. Each of three time intervals of the response function is found to require specific master equation and projection operator. Exact cumulant response functions for the harmonic profiles of the potential energy surfaces leading to Gaussian spectral diffusion are reproduced. The proposed method accounts for the nonequilibrium state of bath at the border of intervals, and can be used to improve calculations of ultrafast non-linear spectra of energy transferring systems.
Theoretical ab initio study of anion–π interactions in inorganic rings by Antonio Bauzá; David Quiñonero; Pere M. Deyà; Antonio Frontera (145-150).
Display Omitted► Energetic and geometric features of unprecedented anion–π complexes involving inorganic rings at the RI-MP2/aug-cc-pVDZ. ► Molecular Electrostatic Potential Surfaces of five six-membered inorganic rings. ► Partitioning of the interaction energy using DFT-SAPT. ► Experimental evidences from the CSD database.Complexes of anions with several six-membered inorganic rings with more or less aromatic character have been optimized at the RI-MP2/aug-cc-pVDZ level of theory. The rings studied are hexazine (N6), boroxine (B3O3H3), borazine (B3N3H6), 1,3,5,2,4,6-triazatriborinine (B3N3) ring, and borthiin (B3S3H3). The anion–π complexes are energetically favorable and the interaction has been characterized by means of the Bader’s theory of ‘atoms-in-molecules’ and partitioning the energy using the SAPT method. Experimental evidence of the importance of this interaction in some inorganic rings has been obtained from the Cambridge Structural Database.