Chemical Physics Letters (v.669, #C)

Contents (iii-xiii).

Display OmittedWe estimate the Hubbard parameters for density-functional-theory (DFT) + U calculations of ZrO2, HfO2, TiO2, and NiO based on calibrating the electronic structure obtained from hybrid functional methods. The electronic density of states is used to assess the parameters and the values thus derived are employed for the full electron and phonon dispersion comparisons. The resulting values account for experimental band gaps and electron correlations that are computationally much less demanding to treat within the simpler DFT + U framework than with the typically more accurate yet expensive hybrid functional methods. Limitations of +U scheme is indicated towards describing TiO2 and HfO2 phase-stability.

Display OmittedThe cyanide anion sensing mechanism of 1,3,5,7-tetratolyl aza-BODIPY (1) has been rigorously investigated using density functional theory and time dependent-density functional theory methods. Mulliken charge distribution and Natural Bond Orbital analysis reveals that cyanide addition may occur at both electrophilic centers with equal probability. The molecular orbital analysis reveals that first excited state ( S 1 ) of 1 is a local excited state with π - π ∗ transition, whereas for 2 (the cyano form of 1), S 1 , a charge-separation state, is found to be responsible for the intramolecular charge transfer (ICT) process which in conjunction with partial configuration change induces fluorescence stimulation in 2.

Display OmittedCopper (I) oxide nanoparticles are synthesized by a simple reaction-diffusion process involving Cu+ ions and sodium hydroxide in gelatin. The mean diameter and the size dispersion of the nanoparticles can be controlled by two experimental parameters, the percent of gelatin in the medium and the hydroxide ion concentration. UV–visible spectroscopy, transmission electron microscopy and X-ray diffraction are used to analyze the size, morphology, and chemical composition of the nanoparticles generated.

Display OmittedGraphite-like C3N3+xHy with s-triazine rings as building blocks were synthesized through a facile one-pot approach. It is surprising that the degree of crystallinity of the synthesized sample at 330 °C (sample CNH-330) was remarkably enhanced by the dilute hydrochloric acid treatment. The mechanism of the acid-induced crystallinity enhancement was preliminarily studied. XRD, FTIR, SEM, photoluminescence spectra, elemental analysis, and XPS were performed to investigate the composition and structure of the obtained samples. The remarkable enhancement of the degree of crystallinity may be attributed to the ordered formation of ammonium-salt-like structure by the reaction of HCl with =NH or ―NH2 in CNH-330.
Keywords: Graphite-like carbon nitride; s-Triazine rings; Chemical synthesis; Acid-induced; Crystallinity enhancement;

Display OmittedIn this paper, we study the effects of the configuration of two Al atoms doped into the unit cell of (7, 0) BNNTs, on their structural and electronic properties in solid state using density functional theory methods. Also, all possible configurations for Al double doped (7, 0) BNNT were investigated. The results showed that with Al doping, band gap decreased. Furthermore, an impurity state appears near the Fermi level when two Al atoms replace two boron atoms of adjacent layers. Contour plots of charge density distribution showed a protuberance surrounding N and B atoms adjacent to the substitute Al atoms.
Keywords: 2×Al doped boron nitride nanotube; Configuration; Electronic properties; Density functional theory; Fermi energy level;

Display OmittedRotationally resolved excitation spectra of TaN molecules, produced in a free-jet, have been studied using laser-induced fluorescence spectroscopy. Thirteen excited electronic states in the energy region, 23,500–30,000 cm−1 have been observed. The molecular constants, Ω-quantum numbers and radiative lifetimes have been determined for these states. Because of the case (c) behavior and absence of the regular energy spacing, the assignments of the excited electronic states of TaN become difficult. The number of observed excited electronic states is significantly larger than currently predicted, indicated a need for additional ab initio calculations.

Atmospheric oxidation of carbon disulfide (CS2) by Zhe Zeng; Mohammednoor Altarawneh; Bogdan Z. Dlugogorski (43-48).
Display OmittedThis contribution investigates primary steps governing the OH-initiated atmospheric oxidation of CS2. Our approach comprises high-level density functional theory calculation of energies and optimisation of molecular structures as well as RRKM-ME analysis for estimating pressure-dependent reaction rate constants. We find the overall reaction OH + CS2  → OCS + SH too slow to account for the formation of the reported experimental products. The initial reaction of OH with CS2 proceeds to produce an S-adduct, SCS(OH). Species-formation history for the system OH + CS2 indicates that, the S-adduct represents the most plausible product with a barrier-less addition process and a stability amounting to 48.5 kJ/mol, in reference to the separated reactants. This adduct then undergoes a bimolecular reaction with atmospheric O2 yielding OCS and HOSO, rather than dissociating back into its separated reactants. We also find that further atmospheric oxidation of the C-adduct (if formed) yields two of the major experimental products namely OCS and SO2. The kinetic analysis provided in this study explains the atmospheric fate of reduced sulfur species, an important S-bearing group in the global cycle of sulfur.

High pressure infrared spectroscopy study on C60∗CS2 solvates by Mingrun Du; Miao Zhou; Mingguang Yao; Peng Ge; Shuanglong Chen; Xigui Yang; Ran Liu; Bo Liu; Tian Cui; Bertil Sundqvist; Bingbing Liu (49-53).
Display OmittedHigh pressure IR study has been carried out on C60∗CS2 solvates up to 34.8 GPa. It is found that the intercalated CS2 molecules significantly affect the transformations of C60 molecules under pressure. As a probe, the intercalated CS2 molecules can well detect the orientational ordering transition and deformation of C60 molecules under pressure. The chemical stability of CS2 molecules under pressure is also dramatically enhanced due to the spacial shielding effet from C60 molecules around in the solvated crystal. These results provide new insight into the effect of interactions between intercalants and fullerenes on the transformations in fullerene solvates under pressure.
Keywords: High pressure; IR spectra; Fullerene; C60∗CS2 solvates;

The power of exact conditions in electronic structure theory by Rodney J. Bartlett; Duminda S. Ranasinghe (54-70).
Display OmittedOnce electron correlation is included in an effective one-particle operator, one has a correlated orbital theory (COT). One such theory is Kohn-Sham density functional theory (KS-DFT), but there are others. Such methods have the prospect to redefine traditional Molecular Orbital (MO) theory by building a quantitative component upon its conceptual framework. This paper asks the question what conditions should such a theory satisfy and can this be accomplished? One such condition for a COT is that the orbital eigenvalues should satisfy an ionization theorem that generalizes Koopmans’ approximation to the exact principal ionization potentials for every electron in a molecule. Guided by this principle, minimal parameterizations of KS-DFT are made that provide a good approximation to a quantitative MO theory.

Physiochemical charge stabilization of silver nanoparticles and its antibacterial applications by G. Vanitha; K. Rajavel; G. Boopathy; V. Veeravazhuthi; P. Neelamegam (71-79).
Display OmittedEnvironmental standardization and stabilization of surface charges of silver nanoparticles (AgNPs) is important in biological systems and interest in bio-interfacial interaction. Different synthesized AgNPs in chemical reduced (AgNO3 (0.01, 0.1 and 0.5 M); NaBH4 and Na3C6H5O7) garnered for analysis of physico-chemical charge stabilization by means of different pH (1–13) and ionic interferences (NaCl, Ca(NO3)2, Na2CO3 and NaNO3). The uniform sized (size: ∼22 nm) and highly charged (zeta potential: −37.9 mV) AgNPs with uniform dispersion remains unaltered in high ionic interferences. Highest antifungal activity of AgNPs against Candida albicans and moderate activity against Staphylococcus aureus are correlated.
Keywords: Silver nanoparticle; Chemical reduction; Zeta potential; Ionic stability; Antimicrobial activity;

t-C8B2N2: A potential superhard material by Dong Wang; Rui Shi; Li-Hua Gan (80-84).
DFT calculations show that C8B2N2 with I-4m2 space group is a stable superhard material with bulk modulus of 383.4 GPa and shear modulus of 383.0 GPa, almost same to those of well-known superhard material c-BN.Display OmittedA potential superhard material C8B2N2 with I-4m2 space group is found and confirmed to be stable with first-principles calculations. The results show that its structure is highly incompressible with bulk modulus of 383.4 GPa and shear modulus of 383.0 GPa. It shows that this material is nearly isotropy with universal anisotropy index of 0.056, and its fractional anisotropy ratio of shear modulus and bulk modulus are 0.0055 and 0.0, respectively. Interestingly, its theoretical bulk modulus, shear modules, Young’s modulus, Poisson’s ratio and Vickers hardness are almost same to those of well-known superhard material c-BN.
Keywords: Superhard materials; Boron-carbon-nitride compounds; Hardness; Elastic modulus; Anisotropy;

Interactions of hypericin with a model mutagen – Acridine orange analyzed by light absorption and fluorescence spectroscopy by Monika Pietrzak; Mariusz Szabelski; Adam Kasparek; Zbigniew Wieczorek (85-91).
Display OmittedThe present study was designed to estimate the ability of hypericin to interact with a model mutagen – acridine orange. The hetero-association of hypericin and acridine orange was investigated with absorption and fluorescence spectroscopy methods in aqueous solution of DMSO. The data indicate that hypericin forms complexes with acridine orange and that the association constants are relatively high and depend on DMSO concentration. The absorption spectra of the hypericin – acridine orange complexes were examined as well. Owing to its ability to interact with flat aromatic compounds, hypericin may potentially be used as an interceptor molecule.
Keywords: Hypericin; Acridine orange; Hetero-association; Absorption; Fluorescence;

Display OmittedThe formation of hemicucurbit[6]uril (hCB[6]) from ethyleneurea with formaldehyde in acidic aqueous solution was explored using density functional methods and the implicit solvation model in water. The oligomerization and cyclization barriers were approximately half lower than that of the iminium formation. Thus, the initial iminium formation is the rate-determining step, and the formation of hCB[6] is kinetically and thermodynamically favored in acidic aqueous solution. In particular, the ‘alternate’ conformation of hCB[6] is enthalpically and entropically preferred over the ‘cone’ conformation, which is consistent with the crystal structure of hCB[6].
Keywords: Hemicucurbit[6]uril; Ethyleneurea iminium; Methylene-bridged ethyleneurea oligomers; Reaction mechanisms; Density functional calculations;

Photoluminescence dynamics in singlet fission chromophore liquid melts by Geoffrey B. Piland; Christopher J. Bardeen (99-103).
Display OmittedThe effect of high temperature melting on the photophysics of three prototypical singlet fission molecules is investigated. Time-resolved photoluminescence is used to look at the melt phase of the molecules tetracene, diphenylhexatriene and rubrene. Chemical decomposition of tetracene precluded any detailed measurements on this molecule. In the diphenylhexatriene melt, a rapid singlet state nonradiative relaxation process outcompetes singlet fission. In the rubrene melt, singlet fission occurs at a rate similar to that of the crystal, but the decay of the delayed fluorescence is much more rapid. The rapid decay of the delayed fluorescence suggests that either the triplet lifetime is shortened, or the fusion probability decreases, or that both factors are operative at higher temperatures.

Polyoxomolybdate formation – A thermodynamic analysis from density functional/PCM calculations by Fernando Steffler; Guilherme Ferreira de Lima; Hélio Anderson Duarte (104-109).
Display OmittedPolyoxomolybdates have been intensely investigated, but their mechanisms of formation are not completely understood. The complex equilibrium of different species is affected by concentration, pH, ionic strength and temperature. It is a challenging system to model using computational chemistry. In the present work, density functional calculations were carried out using the polarizable continuum method to include solvent effects in an effort to provide insight into the mechanism of polyoxomolybdate formation in aqueous solution. We establish a possible sequence of reactions for the formation of small polyoxomolybdates containing up to 8 Mo by addition of the monomeric unit [MoO4]2−.
Keywords: DFT calculations; Polyoxomolybdates; Infrared spectroscopy; Reaction pathways;

Ab initio insight into graphene nanofibers to destabilize hydrazine borane for hydrogen release by Zhao Qian; Himanshu Raghubanshi; M. Sterlin Leo Hudson; O.N. Srivastava; Xiangfa Liu; Rajeev Ahuja (110-114).
Display OmittedWe report the potential destabilizing effects of graphene nanofibers on the hydrogen release property of hydrazine borane via state-of-the-art ab initio calculations for the first time. Interactions of a hydrazine borane cluster with two types of graphene patch edges which exist abundantly in our synthesized graphene nanofibers have been investigated. It is found that both zigzag and armchair edges can greatly weaken the H-host bonds (especially the middle N―H bond) of hydrazine borane. The dramatic decrease in hydrogen removal energy is caused by the strong interaction between hydrazine borane and the graphene patch edges concerning the electronic charge density redistribution.
Keywords: Energy storage; Destabilization; Nanostructured materials; Density functional theory;

Display OmittedAn investigation on dispersion, stability, and agglomeration of water-soluble fullerenol in water was studied via UV–Vis spectroscopy. The results showed that the dispersion quality and stability of water-soluble fullerenol commenced decreasing after 150 h (more than six days) of solution preparation time. Furthermore, increasing the fullerenol concentration in water (Cfullerenol) showed promotion of the agglomeration in lower residence time. Considering the results of DLS and HRTEM micrographs, an average particle size of the fullerenol in the solution was measured to be ∼150 nm after a residence of 2 months highlighting its high agglomeration tendency even at low concentration.
Keywords: Dispersion; Stability; Fullerenol; UV–Vis spectroscopy;

Theoretical modeling of the absorption spectrum of aqueous riboflavin by Laura Zanetti-Polzi; Massimiliano Aschi; Isabella Daidone; Andrea Amadei (119-124).
Display OmittedIn this study we report the modeling of the absorption spectrum of riboflavin in water using a hybrid quantum/classical mechanical approach, the MD-PMM methodology. By means of MD-PMM calculations, with which the effect of riboflavin internal motions and of solvent interactions on the spectroscopic properties can be explicitly taken into account, we obtain an absorption spectrum in very good agreement with the experimental spectrum. In particular, the calculated peak maxima show a consistent improvement with respect to previous computational approaches. Moreover, the calculations show that the interaction with the environment may cause a relevant recombination of the gas-phase electronic states.
Keywords: Riboflavin; Absorption spectrum; Perturbed matrix method; Molecular dynamics; Quantum chemistry;

Display OmittedPoly(vinyl alcohol), PVA, polymer was successfully combined with graphene oxide (GO) and thermally reduced graphene oxide (RGO), respectively, to make composites and characterized for supercapacitor applications. PVA-RGO composite shows excellent electrochemical properties compared to PVA-GO composite. The capacitance of 190 Fg−1 is obtained from PVA-RGO composite which is larger than that (13 Fg−1) of PVA-GO composite. Electrochemical impedance of PVA-RGO is more than ten times smaller than that of PVA-GO at 20 kHz, demonstrating that PVA-RGO composite has a great advantage for supercapacitor applications compared to PVA, GO, RGO, and PVA-GO composite.
Keywords: Polymer composites; Poly(vinyl alcohol); Graphene oxide;

Display OmittedDrug absorption at an acceptable dose depends on the pair of solubility and permeability. There are many potent therapeutics that are not active in vivo, presumably due to the lack of capability to cross the cell membrane. Molecular dynamics simulation of radicicol, diol-radicicol, cyclopropane-radicicol and 17-DMAG were performed at water/octanol interface to suggest interfacial activity as a physico-chemical characteristic of these heat shock protein 90 (HSP90) inhibitors. We have observed that orally active HSP90 inhibitors form aggregates at the water/octanol and DPPC-lipid/water interfaces by starting from an initial configuration with HSP90 inhibitors embedded in the water matrix.
Keywords: HSP90 inhibitors; Water/octanol interface; Molecular dynamics simulation;

Rayleigh-Brillouin scattering in SF6 in the kinetic regime by Yuanqing Wang; Yin Yu; Kun Liang; Wilson Marques; Willem van de Water; Wim Ubachs (137-142).
Display OmittedRayleigh-Brillouin spectral profiles are measured with a laser-based scatterometry setup for a 90° scattering angle at a high signal-to-noise ratio (r.m.s. noise below 0.15% w.r.t. peak intensity) in sulfur-hexafluoride gas for pressures in the range 0.2–5 bar and for a wavelength of λ = 403.0  nm. The high quality data are compared to a number of light scattering models in order to address the effects of rotational and vibrational relaxation. While the vibrational relaxation rate is so slow that vibration degrees of freedom remain frozen, rotations relax on time scales comparable to those of the density fluctuations. Therefore, the heat capacity, the thermal conductivity and the bulk viscosity are all frequency-dependent transport coefficients. This is relevant for the Tenti model that depends on the values chosen for these transport coefficients. This is not the case for the other two models considered: a kinetic model based on rough-sphere interactions, and a model based on fluctuating hydrodynamics. The deviations with the experiment are similar between the three different models, except for the hydrodynamic model at pressures p ≲ 2 bar . As all models are in line with the ideal gas law, we hypothesize the presence of real gas effects in the measured spectra.
Keywords: Rayleigh-Brillouin scattering; SF6 gas; Tenti model; Rough-sphere scattering model;

Display OmittedIn this research, three quaternary ammonium salts containing different counterions, including tetrabutylammonium bromide (TBABr), tetrabutylammonium tetrafluoroborate (TBABF4), and tetrabutylammonium hexafluorophosphate (TBAPF6), were incorporated into [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) as electron transporting layer (ETL). These salts-doped PCBM films revealed higher electron mobility and Fermi levels compared with the un-doped one. Better charge transfer at the interface between perovskite and salts-doped PCBM was also obtained from PL quenching experiments. Inverted perovskite solar cells with the configuration of ITO/PEDOT:PSS/CH3NH3PbI3/PCBM + salts/Ag were fabricated, and the J SC and FF of devices were significantly enhanced using salts-doped PCBM as ETL. The best device based on TBABF4-doped PCBM delivered a power conversion efficiency (PCE) up to 13.41%, which was superior to the one with undoped PCBM layer (PCE  = 8.77%).
Keywords: Quaternary ammonium salts; Counterions; Electron transporting layers; Inverted perovskite solar cells;

Heterodiffusion of Ag adatoms on imperfect Au(1 1 0) surfaces by E. El koraychy; K. Sbiaai; M. Mazroui; R. Ferrando; Y. Boughaleb (150-155).
Display OmittedThe hetero-diffusion of Ag adatoms on imperfect Au(1 1 0) surfaces is studied using Molecular Dynamics (MD) simulations. The atomic interactions are described by an Embedded Atom Method (EAM) potential. Static activation energies governing various diffusion processes (jumps and exchanges) are calculated by quenched MD, finding that activation energies for interlayer mobility at straight step edges are somewhat larger than those on the flat surface in the cross-channel [1 0 0]-direction, while interlayer barriers at kinks are considerably lower. Dynamic activation energies are calculated at high temperature from the Arrhenius plots of different diffusion mechanisms and compared to static barriers.
Keywords: Atomistic dynamics; Diffusion; Gold; Silver; Low-index surfaces; Steps; Kinks; Metallic surfaces;

Ultrafast ring-closing reaction dynamics of a photochromic furan-based difurylethene by A. Khodko; V. Khomenko; Y. Shynkarenko; O. Mamuta; O. Kapitanchuk; D. Sysoiev; N. Kachalova; T. Huhn; S. Snegir (156-160).
Display OmittedThe ultrafast photoinduced ring-closing dynamics of a furan-based difurylethene (YnPhT) has been investigated by femtosecond transient absorption spectroscopy. We performed time-dependent density functional theory (TD-DFT) calculations to explain the experimental results in detail. The sub-picosecond time scale of the ring-closing reaction is comparable with thiophene-based analogues, but oxygen atoms at the photochromic core can avoid adverse interaction between switches and metal contacts in further applications. This observation proves that furan-based diarylethenes are potential optoelectronic elements with an ultrafast optical response.
Keywords: Diarylethenes; Photochromism; Photoswitching; Pump-probe; Femtosecond laser; TD-DFT; Absorption spectra;

Display OmittedThe effects of urea on microstructures of SnO2 during hydrothermal process and its supercapacitor performance were investigated. The sphere SnO2 was formed on Ti plate in hydrothermal solution without urea, while the SnO2 micro-flowers were assembled by numerous few-layered nanopetals due to adding to urea during hydrothermal process. The separated SnO2 nanopetals arrays showed better electrochemical performance than sphere SnO2. The gap between SnO2 nanopetals promoted penetration of the electrolyte and induced high supercapacitive performance.
Keywords: Interfaces; Nanostructures; Microstructure; Electrochemical measurements; X-ray diffraction;

Cooperative coupling of the Li cation and groups to amplify the charge transfer between C60 and corannulene by Gang Sun; Jing Xu; Zhi-Yuan Chen; E. Lei; Xiang-Shuai Liu; Chun-Guang Liu (166-170).
In present work, four complexes (C20H10/C60, C20H10/Li+@C60, C20H5Cl5/Li+@C60 and C20H5(CH3)5/Li+@C60) have been designed to investigate the effect of Li+ cation and substituent on the geometric structures and a series of electronic properties using density functional method. The calculated results indicate that the charge decomposition (CDA) analysis and extend charge decomposition analysis (ECDA) of four complexes have the same sequence. The average d values defined the distances between C60 and corannulene displays the inverse sequence. In other word, the charge transfer between C60 and corannulene increase with decreased distances. The analysis of total density of states (TDOS) and partial density of states (PDOS) is in agreement with the HOMO and LUMO distributions for studied complexes. For C20H10/C60, the HOMO distributes on the C60 cage and C20H10 moiety, and the LUMO solely distributes on the whole C60 cage. For C20H10/Li+@C60, C20H5Cl5/Li+@C60 and C20H5(CH3)5/Li+@C60 complexes, the whole HOMO is just distributed on the C20H10 moiety, and the LUMO is distributed on the C60 cage.Display OmittedIn present work, four complexes have been designed to investigate the effect of Li+ cation and substituent on the geometric structures and a series of electronic properties using density functional theory. The calculated results indicate that the charge decomposition (CDA) analysis and extend charge decomposition analysis (ECDA) of four complexes have the same sequence. The average d values defined the distances between C60 and corannulene display the inverse sequence. Consequently, the cooperative coupling of the Li+ cation and appropriate substituent is predicted to be an effective way to enhance the charge transfer between the C60 and corannulene derivatives.

Microwave synthesis of non-crystalline BCNO phosphors using thiourea as nitrogen source and their tunable luminescence by Jingjing Chen; Yang Zhao; Zhiyong Mao; Dajian Wang; Lijian Bie (171-175).
Display OmittedThiourea was employed as nitrogen source to synthesize BCNO phosphors by a simple microwave heating route. The phase structure, chemical composition, and the dependence of photoluminescent properties on the carbon content and incident excitation light for as-prepared BCNO phosphors were investigated in detail. Non-crystalline powder samples constituted by B, C, N, O elements with a slight of S dopant were identified for the prepared BCNO phosphors. Tunable luminescence induced by carbon content and incident excitation light implies the obtained non-crystalline BCNO phosphors could be used as an excellent candidate for LED conversion phosphor.
Keywords: Phosphors; Luminescence; Microwave heating; Thiourea;

Display OmittedThe dipole moment, linear polarizability and first hyperpolarizability of the 3-methyl-4-nitropyridine-1-oxyde (POM) molecules in solid phase were determined by applying iteratively a supermolecule approach in combination with an electrostatic embedding scheme, in which the surrounding molecules are represented by point charges. It is found that the electrostatic interactions with the surrounding molecules lead to a quasi-vanishing molecular dipole moment for the unit cell, in concordance with the experiment. The environment polarization effect is mild for the linear polarizability but it can be marked for the first hyperpolarizability.

Display OmittedThe Schrödinger-Langevin equation is approximately solved by propagating individual quantum trajectories for barrier transmission problems. Equations of motion are derived through use of the derivative propagation method, which leads to a hierarchy of coupled differential equations for the amplitude of the wave function and the spatial derivatives of the complex action along each trajectory. Computational results are presented for a one-dimensional Eckart barrier and a two-dimensional system involving either a thick or thin Eckart barrier along the reaction coordinate coupled to a harmonic oscillator. Frictional effects on the trajectory, the transmitted wave packet, and the transmission probability are analyzed.
Keywords: Schrödinger-Langevin equation; Complex quantum Hamilton-Jacobi equation; Derivative propagation method; Barrier transmission; Frictional effect;

Display OmittedQuantum mechanical, non-relativistic, non-Born-Oppenheimer (non-BO) calculations are performed for the rovibrational spectrum of H2 excited to the second rotational level. The non-BO wave functions of the considered states are expanded in terms of all-particle explicitly correlated Gaussian functions. The dissociation energies and rovibrational transition energies are calculated and compared with experimental values and values obtained in calculations performed by others. The average interparticle distances are calculated and compared with the corresponding values for HD. They show that H2 is a more “diffuse molecule”. The nuclear-nuclear correlation functions are calculated and plotted to visualize the “non-BO molecular structure” of H2.

Molecular dynamics study on core-shell structure stability of aluminum encapsulated by nano-carbon materials by Qingwen Yi; Jingcheng Xu; Yi Liu; Dong Zhai; Kai Zhou; Deng Pan (192-195).
Display OmittedA ReaxFF reactive forcefield for aluminum-carbon composite system has been developed to investigate structural stability and thermal decomposition mechanism of nano-carbon materials coating aluminum particles. Research results indicated the Al@C particles were structurally stable in a broad temperature range from room temperature up to 2735 K. In particular, the broken carbon cage self-healed to reconstruct a more stable Al@C core-shell structure after Al atoms sequentially departing from carbon cage during thermal decomposition, proffering an effective protection for aluminum surface-activeness.

Quantifying covalent interactions with resonant inelastic soft X-ray scattering: Case study of Ni2+ aqua complex by K. Kunnus; I. Josefsson; S. Schreck; W. Quevedo; P.S. Miedema; S. Techert; F.M.F. de Groot; A. Föhlisch; M. Odelius; Ph. Wernet (196-201).
Display OmittedWe analyze the effects of covalent interactions in Ni 2p3d resonant inelastic X-ray scattering (RIXS) spectra from aqueous Ni2+ ions and find that the relative RIXS intensities of ligand-to-metal charge-transfer final states with respect to the ligand-field final states reflect the covalent mixing between Ni 3d and water orbitals. Specifically, the experimental intensity ratio at the Ni L3-edge allows to determine that the Ni 3d orbitals have on average 5.5% of water character. We propose that 2p3d RIXS at the Ni L3-edge can be utilized to quantify covalency in Ni complexes without the use of external references or simulations.
Keywords: Transition-metal ion; Aqueous solution; Covalent interaction; Resonant inelastic X-ray scattering; Ligand-field state; Charge-transfer state;

Display OmittedNanofluid free convection in presence of Lorentz forces in a permeable semi annulus is simulated using Control Volume based Finite Element Method. Impact of porous media on governing equations is considered by means of Darcy law. Brownian motion impact on properties of nanofluid is taken into account using Koo-Kleinstreuer-Li (KKL) model. Important parameters are inclination angle ( ξ ) , CuO-water volume fraction ( ϕ ) , Hartmann ( Ha ) and Rayleigh ( Ra ) numbers for porous medium. A formula for Nuave is provided. Results indicated that temperature gradient detracts with enhance of Ha but it enhances with rise of ξ , Ra . Heat transfer augmentation enhances with rise of Lorentz forces.
Keywords: Nanofluid; Porous media; Semi annulus; Magnetic field; Natural convection; KKL model;

Display OmittedTheoretical studies have been performed on the kinetics, mechanism and thermochemistry of the hydrogen abstraction reactions of CF3CF2OCH3 (HFE-245mc) and CF3CF2OCHO with OH radical using DFT based M06-2X method. IRC calculation shows that both hydrogen abstraction reactions proceed via weakly bound hydrogen-bonded complex preceding to the formation of transition state. The rate coefficients calculated by canonical transition state theory along with Eckart’s tunnelling correction at 298 K: k1(CF3CF2OCH3  + OH) = 1.09 × 10−14 and k2(CF3CF2OCHO + OH) = 1.03 × 10−14  cm3  molecule−1  s−1 are in very good agreement with the experimental values. The atmospheric implications of CF3CF2OCH3 and CF3CF2OCHO are also discussed.
Keywords: H-abstraction reactions; Kinetics; OH radicals; Atmospheric lifetime; Global warming potential;

Ginzburg-Landau free energy for molecular fluids: Determination and coarse-graining by Caroline Desgranges; Jerome Delhommelle (218-223).
Display OmittedUsing molecular simulation, we determine Ginzburg-Landau free energy functions for molecular fluids. To this aim, we extend the Expanded Wang-Landau method to calculate the partition functions, number distributions and Landau free energies for Ar, CO 2 and H 2 O . We then parametrize a coarse-grained free energy function of the density order parameter and assess the performance of this free energy function on its ability to model the onset of criticality in these systems. The resulting parameters can be readily used in hybrid atomistic/continuum simulations that connect the microscopic and mesoscopic length scales.
Keywords: Ginzburg-Landau free energy; Argon; Carbon dioxide; Water; Mean-field theory; Wang-Landau sampling;

Complete spin contamination-free MP2 method by Manami Nishida; Fang-Han Lim; Yuta Hori; Tomonori Ida; Motohiro Mizuno (224-229).
Display OmittedTo improve the unrestricted second-order Møller-Plesset (UMP2) method, we propose a method in which spin contamination is eliminated due to spin adaptation of the double excitation space based on the unitary group approach (UGA), because the UMP2 calculations intrinsically involve spin contamination from the double excitation space. Numerical results for the activation energies of several radical reactions show that this UGA-UMP2 method offers substantial improvement over the UMP2 method. Furthermore, the UGA-SUMP2 method, which completely eliminates the spin contamination from both the reference and excitation space present in UMP2 calculations, is also formulated.

Display OmittedMP2 calculations with the full aug-cc-pVTZ basis set give a non-planar structure for benzene. Although this non-physical result can be avoided by using the smaller aug-cc-pVDZ basis set or by scaling or deleting selected functions from the aug-cc-pVTZ basis set, such changes to the basis set can result in calculated values of the frequencies of the b2g out-of-plane vibrations that are considerably underestimated. The origin of this behavior is traced to linear dependency problems with the aug-cc-pVDZ and aug-cc-pVTZ basis sets when used for benzene.

How to characterize thermal transport capability of 2D materials fairly? – Sheet thermal conductance and the choice of thickness by Xufei Wu; Vikas Varshney; Jonghoon Lee; Yunsong Pang; Ajit K. Roy; Tengfei Luo (233-237).
Display OmittedThermal transport capability of monolayer 2D materials has been under constant spotlight. However, different definitions of thickness in literature have led to ambiguity towards predicting thermal conductivity values and thus in understanding the heat transfer capability of different monolayer 2D materials. We argue that the same thickness should be used and a ‘sheet thermal conductance’ should be defined as an intensive 2D material property when characterizing the heat transfer capability of 2D materials. When converting literature thermal conductivity values of monolayer materials to this new property, some new features that were not displayed when using different thicknesses show up.

Display OmittedHydrogen (H2) adsorption on the IIA elements doped double-vacancy graphenes (BeG, MgG, CaG and SrG) was studied by using dispersion-corrected density functional theory calculations. Through investigation of different numbers of hydrogen dockings from two directions, it is found that 1H2/BeG, 1H2/MgG, 8H2/CaG and 8H2/SrG are the most stable adsorption configurations for Be, Mg, Ca and Sr doped graphenes, respectively. Atomic radius, electronegativity and ionization potential of the IIA dopant contribute to the dominating adsorption mechanism under specific H2 concentration. The study would facilitate exploration of high performance graphene-related supports for hydrogen storage.

Speciation of uranium and doping induced defects in Gd1.98U0.02Zr2O7: Photoluminescence, X-ray photoelectron and positron annihilation lifetime spectroscopy by Santosh K. Gupta; C. Reghukumar; Nimai Pathak; K. Sudarshan; D. Tyagi; M. Mohapatra; P.K. Pujari; R.M. Kadam (245-250).
Display OmittedBased on photoluminescence spectroscopy it was inferred that uranium stabilizes as both U(IV) as well as U(VI) in Gd2Zr2O7 which was also corroborated using X-ray photo electron spectroscopy (XPS). Absence of equidistant vibronic structure in emission spectrum of Gd1.98U0.02Zr2O7 confirmed that U(VI) stabilizes in the form of UO6 6−. Based on luminescence lifetime it was inferred that majority of UO6 6− stabilizes at both Gd3+/Zr4+ whereas U4+ stabilizes only at Zr4+ sites. The positron lifetime doesn’t change on uranium doping indicating the formation of antisite defect. Infact it is this antisite defect in Gd1.98U0.02Zr2O7 which favours the stabilization of its fluorite phase.