Chemical Physics Letters (v.411, #4-6)
Editorial board (CO2).
Structure and electronic properties of cobalt atoms encapsulated in Si n (n = 1–13) clusters by Li Ma; Jijun Zhao; Jianguang Wang; Qiliang Lu; Lianzhong Zhu; Guanghou Wang (279-284).
A systematic theoretical study of the equilibrium geometries and energetics of cobalt atoms encapsulated in Si n (n = 1–13) clusters and comparison with pure Si n clusters have been performed by density functional theory–generalized gradient approximation calculations combined with a genetic algorithm. Our results reveal that the geometries of bare Si n clusters are substantially modified upon doping of Co atom. Co-doping improves the stability of the clusters after n ⩾ 7. In general, the stability of Si n Co clusters increases with increasing size n. The Si9Co was found as magic-number cluster, and the enhanced stability was explained by the 18-electron rule. The magnetic moment on Co atom inside Si n Co cluster is quenched in all the clusters with n ⩾ 4.
Photocatalytic H2 evolution over a new visible-light-driven photocatalyst In12NiCr2Ti10O42 by Defa Wang; Zhigang Zou; Jinhua Ye (285-290).
A new visible-light-driven photocatalyst In12NiCr2Ti10O42 crystallized in a monoclinic system with the space group P21/a was synthesized by a solid-state reaction method. The photophysical and photocatalytic properties of In12NiCr2Ti10O42 were investigated. The band gap energy was estimated from the UV–vis diffuse reflectance spectrum to be ∼2.14 eV. Efficient H2 was evolved from aqueous methanol solution over Pt (0.2 wt%)/In12NiCr2Ti10O42 powder photocatalyst under visible light irradiation. A possible band structure for In12NiCr2Ti10O42 was proposed in accordance with the crystal structure, photophysical and photocatalytic properties. The present study suggests a promising method for the development of visible-light-responsive photocatalysts with tailed properties by properly utilizing appropriate transition metals.
Measurement of handedness in multiwalled carbon nanotubes by electron diffraction by Zejian Liu; Lu-Chang Qin (291-296).
It is shown that the intensities of electron diffraction from a commensurate multiwalled carbon nanotube are sensitive to the angle of rotation of the nanotube about its axis. This dependence is usable to measure the handedness of the commensurate graphene shells of multiwalled carbon nanotubes. The period of intensity oscillation of the scattering intensity for graphene shells of the same handedness is much larger than that for nanotube shells of opposite handedness. By examining the angular dependence of the scattering intensities, the relative handedness, having the same or opposite handedness, of the commensurate shells can, therefore, be determined.
Ground and excited states of Al2O2 and its anion by Majher Ibna Mannan Sarker; Chang-Seop Kim; Cheol Ho Choi (297-301).
CASSCF, MRMP2, MR-CISD, CCSD(T) and CR-CCSD(T) theories were adopted to study the isomers of Al2O2 and its anion. CR-CCSD(T) and MR-CISD consistently indicate that the linear isomer 2 is the ground state, which is consistent with matrix isolation experiments. All three peaks at 1.88, 2.37 and 5.1 eV in the photoelectron spectra can be readily assigned as 2B3u → 1Ag, 2B3u → 3B3u and 2B3u → 1B3u of isomer 1, respectively indicating that the electronic states of isomer 1 are in better agreements with the photoelectron detachment spectra. These contradicting results may imply that the major isomer of Al2O2 can depend on the experimental conditions.
Protonic conduction model in glasses – A quadratic relation between conductivity and proton concentration by Yoshihiro Abe; Makoto Takahashi (302-305).
Proton conductivity in glasses has been known to be proportional to the square of the concentration of mobile protons of the glasses, but the mechanisms of this quadratic relation are not elucidated yet. A model for the quadratic relation between conductivity and proton concentration in glasses is presented from a view point regarding the proton conduction as a quasi-chemical reaction.
Completely renormalized EOMCCSD(T) method employing independent optimization of the cluster product terms by Karol Kowalski (306-310).
In this Letter, we introduce a new variant of the completely renormalized equation-of-motion method with singles, doubles, and non-iterative triples (CR-EOMCCSD(T)) that employs a novel strategy of handling the cluster product terms that naturally appears in the EOMCC-type expansion for the trial wavefunction. The new parametrization, as shown on several examples, including the N2, C2, and the ozone molecule, assures the required flexibility of the CR-EOMCCSD(T) approach especially in dealing with the challenging excited states primarily dominated by double excitations.
Understanding learning control of molecular fragmentation by David Cardoza; Mark Baertschy; Thomas Weinacht (311-315).
We analyze the physical mechanisms underlying control over molecular fragmentation in a family of similar molecules using shaped ultrafast laser pulses. Our interpretation of the control mechanism in one molecule allows us to predict the nature and degree of control possible in the others. The predictions are verified and variations in the control are discussed. This study points to systematic behavior in chemical reactions of similar species driven by photonic reagents.
Absolute luminescence efficiency and photonic band-gap effect of conjugated polymers with top-deposited distributed Bragg reflectors by Luana Persano; Elisa Mele; Andrea Camposeo; Pompilio Del Carro; Roberto Cingolani; Dario Pisignano (316-320).
We study the effects of the deposition of a photonic crystal (PhC) structure, namely a distributed Bragg reflector, on a light-emitting conjugated polymer. The hybrid organic/PhC system is realised by a novel low-temperature reactive electron beam deposition, suitable for the direct fabrication of high-reflective mirrors onto organic soft matter. We investigated the photoluminescence absolute quantum efficiency of the system, finding a yield of 30% after the mirror deposition. We found evidence for the modulation of the output spectra by the photonic band-gap of the coupled PhC, and for the polarisation splitting (as large as 140 meV) of the emitted light.
The torsional potential in 2,2′-bipyrrole revisited: High-level ab initio and DFT results by J.C. Sancho-Garcı́a; A. Karpfen (321-326).
A systematic study of torsional potentials for inter-ring rotation in 2,2′-bipyrrole is accomplished. Highly accurate calculations were performed at the second-order Møller–Plesset theory (MP2) and at the very demanding coupled-cluster with single, double, and perturbatively estimated triple excitations CCSD(T) level, together with the hierarchy of (aug)-cc-pVnZ basis sets. These large-scale state-of-the-art calculations ensure virtual convergence in both N- and one-particle space. The reliability of density-functional theory (DFT) is thoroughly assessed along the whole rotational profile by root-mean-squared energy differences with respect to benchmark values. The best agreement is obtained for large fractions of Hartree–Fock (HF) exchange introduced into the functionals.
Do DC-Chol/DOPE-DNA complexes really form an inverted hexagonal phase? by Giulio Caracciolo; Ruggero Caminiti (327-332).
Using synchrotron small angle X-ray scattering and energy dispersive X-ray diffraction, we have found that cationic liposomes made of the monovalent cationic lipid, 3-[N-(N,N-dimethylaminoethane)-carbamoyl]cholesterol (DC-Chol) and the neutral lipid dioleoylphosphatidylethanolamine (DOPE) condense DNA molecules forming complexes (DC-Chol/DOPE-DNA) which are not assembled in an inverted hexagonal structure as recently reported, but, conversely, form a well-ordered lamellar liquid-crystalline phase with distinct regimes of DNA packing density.
Theoretical prediction of a novel inorganic fullerene-like family of silicon–carbon materials by Ruoxi Wang; Dongju Zhang; Chengbu Liu (333-338).
In an effort to search for new inorganic fullerene-like structures, we designed a series of novel silicon–carbon cages, (SiC) n (n = 6–36), based on the uniformly hybrid Si–C four- and six-membered-rings, and researched their geometrical and electronic structures, as well as their relative stabilities using the density function theory. Among these cages, the structures for n = 12, 16, and 36 were found to been energetically more favorable. The calculated disproportionation energy and binding energy per SiC unit show that the (SiC)12 cage is the most stable one among these designed structures. The present calculations not only indicate that silicon–carbon fullerenes are promised to be synthesized in future, but also provide a new way for stabilizing silicon cages by uniformly doping carbon atoms into silicon structures.
Excitation wavelength dependence of solvation dynamics of coumarin 480 in a lipid vesicle by Pratik Sen; Taku Satoh; Kankan Bhattacharyya; Keisuke Tominaga (339-344).
Excitation wavelength dependence of solvation dynamics and fluorescence anisotropy of coumarin 480 (C480) is studied using picosecond time resolved emission spectroscopy in a dimyristoyl-phosphatidylcholine (DMPC) vesicle. In the DMPC vesicle, C480 exhibits 10 nm red edge excitation shift indicating the heterogeneous nature of the microenvironment. The dynamic Stokes shift (Δν) and solvation time of C480 in DMPC vesicle decreases with increase in the excitation wavelength (λ ex). The decay of the emission spectral width and fluorescence anisotropy of C480 in DMPC also depend on λ ex.
Microscopic dissolution process of Na3 in water clusters by Akimasa Fujihara; Chiyoko Miyata; Kiyokazu Fuke (345-349).
Dissolution of sodium trimer in water clusters is studied by photoelectron and photodissociation spectroscopies of Na 3 - ( H 2 O ) n . The photoelectron spectrum is found to exhibit transitions from the anion to the neutral ground and first excited states merge into each other with increasing n. The huge spectral change is ascribed to the dissolution of Na 3 - core into Na 2 - and Na based on ab initio calculations for the structures and energies of these clusters. The theoretical prediction is confirmed with the photodissociation experiments of Na 3 - ( H 2 O ) 3 . On the basis of these results, we discuss the stepwise dissolution of metal aggregates in water clusters.
Ionization and dissociation of simple molecular ions in intense infrared laser fields: Quantum dynamical simulations for three-dimensional models of HD+ and H 2 + by G.K. Paramonov (350-356).
The dynamics of multiphoton excitation of HD+ and H 2 + in quasi-resonant infrared intense laser fields (I 0 = 1.18 × 1014 W/cm2) is studied by the numerical solution of the time-dependent Schrödinger equations for the systems with explicit treatment of the nuclear vibrations and the electron motion beyond the Born–Oppenheimer approximation. It has been found, in particular, that on the time scale of 400 fs the overall ionization yield is about 40% for HD+, but only about 0.45% for H 2 + while in accordance with the tunnel (or field) ionization mechanism at least comparable ionization yields could be expected for HD+ and H 2 + . The physical reason for this remarkable difference is that the nuclear motion is excited directly by the strong infrared laser field in HD+, but not in H 2 + .
Mechanism of the electro-optic effect in BaTiO3 by X.Y. Meng; Z.Z. Wang; Chuangtian Chen (357-360).
We present an ab initio calculation to further verify our earlier theoretical model. The result shows that the origin of the electro-optic effect in BaTiO3 crystal comes mainly from the displacement of the Ti4+ ions relative to the oxygen ions in the octahedron (TiO6) groups. The displacement of the Ti4+ ions lead to changes of the band wave functions of the electrons in the crystal, which produce the changes of the refractive indices. The calculation further reveals the physical meaning of parameters used in the theoretical model.
Bulk-quantity synthesis of single-crystalline indium nitride nanobelts by Shudong Luo; Weiya Zhou; Zengxing Zhang; Xinyuan Dou; Lifeng Liu; Xiaowei Zhao; Dongfang Liu; Li Song; Yanjuan Xiang; Jianjun Zhou; Sishen Xie (361-365).
Wurtzite InN nanobelts have been synthesized in bulk quantities by means of in situ nitriding indium oxide powders in ammonia flux, with a high yield, high purity and good reproducibility. As-synthesized InN nanobelts have typical widths of 1–5 μm, thickness of 40–50 nm and lengths of tens to hundreds of microns imaged by scanning electron microscopy. Transmission electron microscopy reveals that the synthesized InN nanobelts are single crystalline in [0 0 0 1] orientation and preferentially enclosed by top surfaces ± ( 0 1 1 ¯ 0 ) /side surfaces ± ( 2 1 ¯ 1 ¯ 0 ) . Photoluminescence spectrum of InN nanobelts at room temperature shows a strong emission peak centered at 704 nm (1.76 eV).
Metastable dissociation of doubly charged ions produced from toluene: Kinetic energy release upon charge separation and H2 elimination by S. Feil; O. Echt; K. Głuch; V.G. Hasan; S. Matt-Leubner; T. Tepnual; V. Grill; A. Bacher; P. Scheier; T.D. Märk (366-372).
Doubly charged ions produced by electron impact ionization of toluene undergo metastable decomposition. We have determined decay channels for C 7 H y 2 + ( y = 6 – 8 ) and the average kinetic energy release (KER) by applying the MIKE scan technique. We observe several reactions that have not been reported previously, including H2 elimination from C 7 H 8 2 + . The KER distribution for H2 loss shows no evidence for a reverse barrier. The average KER is <0.1 eV; it exhibits a distinct time dependence and isotope effect. On the other hand, some charge separation reactions reported previously in the literature are likely due to isotopic interference.
Characterization and nonlinear optical property of a multi-walled carbon nanotube/silica xerogel composite by Zhan Hongbing; Zheng Chan; Chen Wenzhe; Wang Minquan (373-377).
A multi-walled carbon nanotube (MWNT)/silica xerogel composite was prepared by sol–gel technique and characterized by Raman spectroscopy and transmission electron microscopy. The nonlinear optical property of MWNTs in liquid suspension and solid state matrix were investigated separately by open aperture Z-scan method, using 532 and 1064 nm nanosecond laser pulses. The results show that both MWNT composite and suspension are nonlinear efficient at 1064 and 532 nm, while MWNT composite may be more suitable for practical use because of their better nonlinear effect and possibly nondestructive nonlinear absorption mechanism.
Spin dynamics of carrier generation in a photoconductive C60-doped poly(N-vinylcarbazole) film by Toshinari Ogiwara; Tadaaki Ikoma; Kimio Akiyama; Shozo Tero-Kubota (378-383).
The magnetic field effects on the carrier yield have been studied to clarify the spin dynamic process during photoinduced carrier generation in a fullerene (C60)-doped poly(N-vinylcarbazole) (PVCz) film. The charge transfer (CT) complex of C60 and the carbazole (Cz) chromophore is selectively excited. The total number of carriers that escaped from the geminate pairs decreases in the presence of magnetic fields, which arises from a hyperfine mechanism of the distant ion pairs involving C 60 - and Cz+. Time-resolved EPR measurements verify that the excited triplet state of C60 is produced via its excited singlet state generated from the contact ion pair. The competitive formation processes of distant ion pairs and the excited states of C60 from the contact ion pair are discussed.
Electronic structure properties of carbon nanotubes obtained by density functional calculations by Urban Borštnik; Milan Hodošček; Dušanka Janežič; István Lukovits (384-388).
The total energies, atomic charges, and energy band gaps of (3,3) and (7,7) armchair and (6,0) and (12,0) zig-zag carbon nanotubes (CNTs) of various lengths were determined using density functional ab initio (DFT) calculations. Armchair CNTs were found to be less reactive than zig-zag CNTs. The calculated band gap, which accounts for metallic character, was smaller in (3n,0) zig-zag tubes than in armchair CNTs and in both cases the band gaps decreased with increasing lengths of the tubes. However, frontier orbitals, which account for conductivity, were localized in zig-zag but delocalized in armchair tubes.
Fluorite-to-Aurivillius phase transformation kinetics in sol–gel derived SBT thin films by Yun-Mo Sung; Woo-Chul Kwak (389-394).
SBT films with different thickness were fabricated using a sol–gel processing and spin coating. The as-coated films were heated at 600 °C for the crystallization to fluorite and then further heated at 740–770 °C for the phase transformation to Aurivillius. It was found that the phase transformation kinetics apparently increased with thickness up to ∼390 nm, and then it decreased above this value. The Johnson–Mehl–Avrami (JMA) isothermal kinetics analyses showed the dependence of nucleation and crystal growth modes on the film thickness. From the Arrhenius plots the activation energy values for the phase transformation were determined for SBT films with different thickness.
Calculations of the Raman spectra of C60 interacting with water molecules by Maher S. Amer; James A. Elliott; John F. Maguire; Allan H. Windle (395-398).
Molecular mechanics and semi-empirical quantum mechanical calculations were conducted to investigate the effect of water interaction on the Raman spectra of C60 fullerene. It was found that the frequency of the fullerene surface modes Hg(7), A2g, and Hg(8) shifts to higher wavenumbers as the number of interacting water molecules increased. The Raman peak shift was non-linear and showed an intermediate plateau related to structural changes in the surrounding water molecules. The average C–C bond length was found to be essentially constant within 0.002 Å, indicating constant volume for the fullerene molecule. The current results confirm the suitability of C60 in applications as nanosensor to investigate liquid structures and transitions.
Second-harmonic generation and theoretical studies of protonation at the water/α-TiO2 (1 1 0) interface by Jeffrey P. Fitts; Michael L. Machesky; David J. Wesolowski; Xiaoming Shang; James D. Kubicki; George W. Flynn; Tony F. Heinz; Kenneth B. Eisenthal (399-403).
The pH of zero net surface charge (pHpzc) of the α-TiO2 (1 1 0) surface was characterized using second-harmonic generation (SHG) spectroscopy. The SHG response was monitored during a series of pH titrations conducted at three NaNO3 concentrations. The measured pHpzc is compared with a pHpzc value calculated using the revised MUltiSIte Complexation (MUSIC) model of surface oxygen protonation. MUSIC model input parameters were independently derived from ab initio calculations of relaxed surface bond lengths for a hydrated surface. Model (pHpzc 4.76) and experiment (pHpzc 4.8 ± 0.3) agreement establishes the incorporation of independently derived structural parameters into predictive models of oxide surface reactivity.
A density-functional study of the energetics of H2O dissociation on bimetallic Pt/Ru nanoclusters by Yasuyuki Ishikawa; Robert R. Diaz-Morales; Alejandro Perez; Marius J. Vilkas; Carlos R. Cabrera (404-410).
A density-functional study of homolytic and heterolytic O–H bond cleavage in the dehydrogenation reaction of H2Oads has been carried out on ruthenium sites in bimetallic Pt(1 1 1)/Ru nanoclusters of varying surface morphology. The Ru sites are either produced by co-deposition, forming an alloy, or by sequential deposition. The reaction energies and activation barriers for H2Oads dissociation on the Ru sites are estimated. On the basis of the energetics of H2Oads(Ru) dissociation on the Ru sites, the sequentially deposited Pt/Ru bimetallic cluster surface is predicted to be more catalytically active in water activation and COads oxidation than the alloy surface.
Are resonance-assisted hydrogen bonds ‘resonance assisted’? A theoretical NMR study by Ibon Alkorta; José Elguero; Otilia Mó; Manuel Yáñez; Janet E. Del Bene (411-415).
The concept of resonance-assisted hydrogen bonds (RAHBs) is one of the most frequently used concepts in structural chemistry. Computed equation-of-motion coupled cluster singles and doubles (EOM–CCSD) O–O and N–N coupling constants through intramolecular X–H–X hydrogen bonds (2h J X–X) and MP2 1H chemical shifts of the X–H–X protons have been used to investigate RAHBs in model saturated and unsaturated systems. The computed results suggest that the NMR properties of these molecules do not receive significant contributions from resonance, but are a consequence of the σ-skeleton framework.
Theoretical study on magneto-structural correlation in axially coordinated complexes of copper(II) with nitronyl nitroxide radical by Cheng-Bu Liu; You-Min Sun; Bin Zheng; Ruo-Xi Wang (416-422).
The theoretical study on magneto-structural correlation in axially coordinated copper(II)–nitronyl nitroxide complex has been performed using the broken symmetry approach with the framework of density functional theory. The exchange interaction between Cu(II) ion and nitronyl nitroxide radical is propagated through a mechanism involving interaction between orthogonal orbitals. The spin density population shows that the electron transfer takes place from the Cu(II) ion to nitronyl nitroxide radical. The magneto-structural correlations indicate that both the variations of Cu–O distance and the Cu–O–N angle have significant influence on the magnetic exchange interaction.
Is there a coupling between rotational and translational motion of methane in silicalite-1 and AlPO4-5? by S. Fritzsche; T. Osotchan; A. Schüring; S. Hannongbua; J. Kärger (423-428).
Methane, although often treated approximately as a spherical Lennard–Jones particle, has merely a tetrahedral shape. While moving in zeolites, the interaction of the molecule with the walls will cause a fluctuating angular momentum of this guest molecule. In zeolites containing channels, as it is the case with silicalite-1 or AlPO4-5, adsorbed guest molecules move along channels and change to other channel types at channel intersections. The question arises whether or not the corrugation of the zeolite channels leads to a coupling of rotational and translational motions. It shall be shown, however, that for methane in silicalite-1 and AlPO4-5 the two kinds of motion are uncoupled. The relaxation behavior of translational and angular momentum shows different patterns, although in both cases the relaxation time is on the same order of magnitude.
Non-activated pathway in angle-resolved study of H2 molecules produced in the abstraction reaction of incident H atoms on hydrogenated Si(1 0 0) by R. Bisson; S.H. Yang; L. Philippe; M. Châtelet (429-433).
We present the first angle resolved study of H2 molecules coming from a hydrogenated Si(1 0 0)-2 × 1 surface at 650 K exposed to a chopped hydrogen atomic beam under fixed incidence angle. We get an exceptionally wide angular distribution, which can be fitted by cos n θ with n < 1. We interpret this new result by a non-activated pathway involving collision induced desorption and site-specific hot atom abstraction on two neighbor Si dimers inside a dimer row after passing through a transition state similar to the inter-dimer 4H reaction path, recently proposed in a H2/Si(1 0 0)-2 × 1 system.
Experimental approach to the anion problem in DFT calculation of the partial charge transfer during adsorption at electrochemical interfaces by V.A. Marichev (434-438).
In DFT calculation of the charge transfer (ΔN), anions pose a special problem since their electron affinities are unknown. There is no method for calculating reasonable values of the absolute electronegativity (χ A) and chemical hardness (η A) for ions from data of species themselves. We propose a new approach to the experimental measurement of χ A at the condition: ΔN = 0 at which η values may be neglected and χ A = χ Me. Electrochemical parameters corresponding to this condition may be obtained by the contact electric resistance method during in situ investigation of anion adsorption in the particular system anion-metal.
Unconventional interaction in N(P)-related systems by Weizhou Wang; Yu Zhang; Kaixun Huang (439-444).
Non-conventional intramolecular and intermolecular interactions have been investigated employing glycine (VIIp), NH3⋯HCl, NH3⋯H2O and PH3⋯H2O as model systems. Geometries and harmonic frequencies were determined at a correlated ab initio level, which shows a elongating of the Cl–H or O–H bond of the proton donor and a red-shifting of the corresponding Cl–H or O–H bond stretching frequency. NBO analysis indicates there is a significant charge transfer from the proton acceptor to the proton donor. However, this type of interaction cannot be called hydrogen bond according to a comparative analysis of electron density topology in the four systems.
Complex-assisted one-step synthesis of ion-exchangeable titanate nanotubes decorated with CdS nanoparticles by Ákos Kukovecz; Mária Hodos; Zoltán Kónya; Imre Kiricsi (445-449).
Trititanate nanotubes were prepared from anatase TiO2 in 10 M Na2S solution kept at 130 °C for 2 weeks. On the basis of this reaction, we devised a novel synthesis method which allows the preparation of titanate nanotubes decorated with CdS nanoparticles in one step. The key feature of the suggested method is controlling the rate of CdS formation by introducing Cd2+ ions as a Cd–EDTA complex into the synthesis mixture. The nanotubes obtained are several hundred nm long, tend to aggregate into rod-like structures and are fully covered by CdS nanoparticles with an average diameter of ∼5.3 nm.
Effect of protonation on the electronic structure of 1,3,5-trimethylenebenzene triradical by Hue Minh Thi Nguyen; Tran Thanh Hue; Minh Tho Nguyen (450-456).
1,3,5-Trimethylenebenzene (TMB, C9H9) is a prototypical hydrocarbon triradical. CASPT2/ANO-L calculations confirm that TMB has a quartet ground state with a 2 B 1 – 4 A 1 ″ gap of 12.4 ± 2.0 kcal/mol; both 2B1 and 2A2 states are quasi-degenerate. C 9 H 9 - has nearly degenerate 3B2, 3A1 and 1A1 states and C 9 H 9 + nearly degenerate 3A1, 1A1 and 3B2 states. Exocyclic protonation is favoured over ring-protonation; both processes induce a low-spin doublet ground state. Ionization energy, electron affinity, proton affinity are: IEa(TMB) = 7.5 ± 0.2 eV, EA(TMB) = 22 ± 2 kcal/mol, PA(C9H9) = 235 ± 2 kcal/mol.
The asymptotic region of the potential energy surfaces relevant for the O(3P) + SO(X3Σ−) reaction by Isabelle Navizet; Pavel Rosmus (457-462).
The potential energy surfaces (PESs) and the spin–orbit couplings for all states of sulfur dioxide correlating with the lowest O(3P) + SO(X3Σ−) asymptote have been calculated in the bond formation region employing correlated electronic wavefunctions. The PESs are found to be strongly anisotropic along the bending coordinate. For linear OS⋯O approach, the Σ states lie below the Π states; for the O⋯OS orientation the Π/Σ ordering is opposite. For perpendicular approaches their A′ components form avoided crossings. The electron spin quantum number is no longer a good quantum number for geometries where the multiplets come close together.
Defects and domain structures in SBA-16 mesoporous films with 3D cubic structure by Ruihong Wang; Qing Chen; Fu Rong Chen; Ji Jung Kai; Lian-Mao Peng (463-467).
We report here the observations and analysis of defects and domain structures in SBA-16 mesoporous films on molecular level using high resolution transmission electron microscopy. The films were made by dip-coating and have layered structure. Domain boundaries both perpendicular and parallel to the substrate were observed. It was found that while some observed low angle and high angle domain boundaries are similar to that found in normal crystals, distortions analogue to that existing in liquid crystal were also observed. The results are shown to provide useful information for understanding the growth mechanism and the properties of the film.
Nature and electronic properties of Y-junctions in CNTs and N-doped CNTs obtained by the pyrolysis of organometallic precursors by F.L. Deepak; Neena Susan John; A. Govindaraj; G.U. Kulkarni; C.N.R. Rao (468-473).
Carbon nanotubes (CNTs) and N-doped CNTs with Y-junctions have been prepared by the pyrolysis of nickelocene–thiophene and nickel phthalocyanine–thiophene mixtures, respectively, the latter being reported for the first time. The junctions are free from the presence of sulfur and contain only carbon or carbon and nitrogen. The electronic properties of the junction nanotubes have been investigated by scanning tunneling microscopy. Tunneling conductance measurements reveal rectifying behavior with regions of coulomb blockade, the effect being much larger in the N-doped junction nanotubes.
Molecular dynamics simulation of the sodium octanoate micelle in aqueous solution by André Farias de Moura; Luiz Carlos Gomide Freitas (474-478).
A 20 ns molecular dynamics simulation was performed with a realistic model system of sodium octanoate micelles in aqueous solution. The system comprised three micellar aggregates, each containing 15 monomers, and 15 free octanoate monomers. The initial configuration relaxed within 2 ns, mostly due to the fusion of aggregates and the exchange of monomers between the aggregates and the solution. The process led to a decrease in the total number of octanoate clusters and to an increase in the average aggregation number and micellar radius, observations in agreement with experimental results.
Quick formation of single-crystal nanocubes of silver through dual functions of hydrogen gas in polyol synthesis by Yun Tack Lee; Sang Hyuk Im; Benjamin Wiley; Younan Xia (479-483).
High yields of 40-nm silver nanocubes were produced in 20 min by bubbling hydrogen gas through a conventional polyol synthesis. Hydrogen gas both accelerated the reduction rate and generated nitric acid in situ. Twinned seeds were selectively dissolved by balancing the reduction rate with etching by nitric acid, so that only single crystals were produced.
Reexamination of the structures and energies of Li2C2 and Li4C4 by Sang Yeon Lee; Bong Hyun Boo; Heun Kag Kang; Dongeun Kang; Ken Judai; Junichi Nishijo; Nobuyuki Nishi (484-491).
The structures and energies of Li2C2 and Li4C4 have been reexamined by DFT and MP2 methods using a variety of basis sets of 6-311+G(3df) and cc-pVXZ(X = T,Q,5). Two low-lying isomers are found as the local minima on the potential energy surfaces of Li4C4. The lowest energy structure is shown to be multiply bridged D2h form. A newly found quadruply bridged Ci form is found to be a local minimum, lying in energy above D2h form by 22 kJ/mol in the energy. Also the energetics of high-lying isomers such as tetralithiotetrahedrane isomers were evaluated and discussed.
A generalized Kohn–Sham scheme by Á. Nagy (492-495).
A generalized Kohn–Sham scheme in which the correlation energy disappears is presented. Therefore, exchange energy has to be determined instead of the exchange-correlation energy and it can be calculated very accurately. Contrary to the standard density functional theory, in the generalization presented here the density can change by a constant factor: ϱ ζ (r) = ϱ(r)/ζ, proposed by Chan and Handy a couple of years ago. Making use of the method a simple approximate relation for the correlation energy of the original Kohn–Sham scheme is derived.
Second-order nonlinear optical activity vs. chromophore content in simple organic glass/PMMA system by Seung Mook Lee; Woong Sang Jahng; Jin Hyun Lee; Bum Ku Rhee; Ki Hong Park (496-500).
A simple organic glass with a connection of two nonlinear optical (NLO) moieties was synthesized by condensation reaction of alkyl-substituted dibenzaldehyde with barbituric acid. This organic glass with T g of 81 °C was formed to be optically transparent films without any phase separation even at the highest chromophore content (100 wt% loading without host matrix). The second-order NLO properties with various organic glass/PMMA composition systems were systematically studied by Maker fringe method at a wavelength of 1064 nm. We demonstrate that second-order optical nonlinearity of this organic glass/PMMA system can be progressively enlarged with increasing chromophore loading from 0 to 100 wt%.
Effect of central metal on intra-molecular exciplex of porphyrin–fullerene double linked dyad by V. Chukharev; N.V. Tkachenko; A. Efimov; H. Lemmetyinen (501-505).
The photoinduced electron transfer reaction of porphyrin–fullerene dyads occurs through an intermediate state, previously identified as a preformed intramolecular exciplex, emitting in the near infrared region (NIR). It can also be seen as a weak absorption band in NIR commonly called the charge transfer absorption band. A detailed analysis of the absorption and emission features of a series of double-linked dyads reported in this Letter leads to the conclusion that the state is characterized by a shift of 40% of the electron density from the porphyrin donor to the fullerene acceptor.
Mass analyzed threshold ionization spectroscopy of p-cyanophenol cation and the CN substitution effect by Changyong Li; Manik Pradhan; Wen Bih Tzeng (506-510).
The adiabatic ionization energy of p-cyanophenol has been determined to be 72 698 ± 5 cm−1 (9.0134 ± 0.0006 eV) on the basis of mass analyzed threshold ionization (MATI) spectrscopy. Analysis of the newly obtained MATI spectra gives the respective frequencies of 399, 517 and 820 cm−1 for the ring deformation 6a, C–CN bending, and breathing vibrations of the p-cyanophenol cation. Comparing these experimental data with those of phenol leads to a better understanding about the influence of the CN substituent on the ionization energy and molecular vibration.
Study of mechanism of photogenerated charge transfer in nano-TiO2 by Z.H. Li; D.J. Wang; P. Wang; Y.H. Lin; Q.L. Zhang; M. Yang (511-515).
The electric field induced dipole model which is useful for interpreting the mechanism of photogenerated charge transfer in nano-TiO2 has been introduced using photovoltage electric field scanning technique. Based on above model, we suppose that diffusion mechanism controls the photogenerated charge transfer in nano-TiO2. Also, we have studied the behavior of charge transfer in nano-TiO2 under external electric field and found that the photogenerated charge transfer is controlled by different transfer mechanisms under different applied external electric field.
Raman spectra of hydrogen and deuterium adsorbed on a metal–organic framework by Andrea Centrone; Diana Y. Siberio-Pérez; Andrew R. Millward; Omar M. Yaghi; Adam J. Matzger; Giuseppe Zerbi (516-519).
The Raman spectra of H2 and D2 adsorbed on metal–organic framework-5 at various pressures (H2: 12.8 and 30.3 bar; D2: 2.2–24.5 bar) and temperatures (H2: 298 K; D2: 40–300 K) have been recorded. The shifts observed in the vibrational modes of the gases indicate that physisorption is responsible for the attractive interactions between the gas and the framework; these interactions are larger with respect to those detected for carbon materials.
Author Index (520-529).