The geometry, vibrational frequencies, thermochemistry, quadrupole moments and electronic structure of C2Na2: Comparison with C2Li2, C2H2, C2F2 and C2Cl2

The electronic structure of Na₂C₂ is studied using ab initio electronic structure methods and is compared to the companion molecule Li₂C₂. Both the linear D_∞h and planar structures are minima on the ground state potential surface with the planar D_2h conformation being the lowest energy form, similar to Li₂C₂. At the CCSD(t) level the planar form is more stable that the linear by 11.2 kcal/mol as compared with 7.34 kcal/mol for Li₂C₂. Both molecules are significantly ionic. The vibrational frequencies, atomization energy at 0 K, D₀, and the standard enthalpy of formation, are calculated and compared to those of Li₂C₂ as well as HCCH, FCCF and ClCCCl. We find D₀ and to be 331.1 and 84.92 kcal/mol for Li₂C₂ and 298.3 and 93.25 kcal/mol for Na₂C₂. We calibrate these by calculating the same quantities for HCCH, FCCF and ClCCCl.     

Theoretical studies on the aromaticity of η-cyclopentadienyl cobalt dithiolene complexes

Some η⁵-cyclopentadienyl cobalt dithiolene complexes CpCoS₂C₂R₂ have been optimized at B3LYP/6-311++G(d) level. The optimized geometries agree well with experiment. The analyses of nature bond orbital and nucleus-independent chemical shift (NICS) at B3LYP/6-311++G(d) and GIAO-B3LYP/6-311++G(d) levels reveal the aromatic character of the η⁵-cyclopentadienyl cobalt dithiolene complexes. However, their aromaticity is weaker than that of the isolated . There are two reasons for the change of heterocyclic aromaticity of the metal dithiolene in the η⁵-cyclopentadienyl cobalt dithiolene complexes with respect to that of the isolated . The better equalization of bond lengths in the isolated cation is the first reason. The other reason is that the contribution to the NICS from the metallic cobalt atom is much larger in the isolated cation . The planar character of cyclopentadienyl is destroyed slightly in the complexes. At the same time, the size of cyclopentadienyl (Cp) becomes bigger than the isolated Cp⁻¹ and this is caused by the cobalt atom in the pentagon. The π-electron delocalization causes stronger aromaticity of the Cp in the complexes than that of the isolated Cp⁻¹.     

Theoretical studies on fluorescence of phenol and 1-naphthol in both acid and alkali solutions

The molecular structures of the ground state and the first singlet excited state for , C₆H₅OH, C₆H₅O⁻, , C₁₀H₇OH and C₁₀H₇O⁻, the forms of phenol and 1-naphthol in acid and alkali solutions, were optimized by ab initio HF and configuration interaction with singlet excitations (CIS) method, respectively. Their fluorescent spectra were obtained by the time-dependent density functional theory (TD-DFT) using the B3LYP method with the 6-31+G (d) basis set. The frontier molecular orbital characteristics, fluorescent spectrum and proton affinities had been analyzed systematically in order to study different fluorescence of phenol and 1-naphthol in acid and alkali solutions. It was found that C₆H₅OH and are the main forms of phenol in acid solution, but C₆H₅O⁻ in alkali solution; C₁₀H₇OH and C₁₀H₇O⁻ are the main forms of 1-naphthol in alkali solution, but in acid solution. The calculated results are in good agreement with the experimental data.     

The intermolecular potential function of Smith–Thakkar type for C60

The intermolecular potential function of Smith–Thakkar type for C₆₀ has been proposed, and its expression is as follows

The unit of u(r) is J/mol, r is the distance between two C₆₀ molecules center and the unit is nm. Some properties of C₆₀ in the gas and crystal have been studied using the interaction potential of Smith–Thakkar type, such as stability of C₆₀ crystals, virial coefficient and lattice dynamics.     

Long-term prediction of compressive creep development in expanded polystyrene

The results obtained in investigating the creep of expanded polystyrene (EPS) boards under compressive stress are presented. Power and exponential equations were used for describing creep compliance. It was found that the curves of creep compliance approximated by both equations adequately represent the research results, taking into account the scatter of the experimental data. Based on the calculation and empirical estimate of long-term creep of EPS under compressive stress σ_c=(0.25–0.45)σ_10%, its creep compliance was determined for a period of 10 years in the future. The dependence of on the density of polystyrene boards and the value of long-term compressive stress σ_c was established. The expected values of creep strain development in expanded polystyrene boards EPS 80–EPS 250 under constant compressive stress σ_c=(0.25–0.45)σ_10% are presented for the prediction period of 10 years. To obtain the expected creep values for any other period of time in the interval of 5T50 years, the values of should be multiplied by the empirical coefficient .     

Transport properties of acetone aqueous solutions: molecular dynamics simulation and NMR studies

Two quantities η_rel and are applied to study the nonideal acetone–water association mixture. An all-atom acetone model and a TIP5P water model have been adopted for molecular dynamics simulation. We study the transport properties of the system comparing the 's of strong hydrogen bond and weak contact based on transport properties, MD simulations together with NMR experimental data and find good agreement of concentration dependence, which exhibits the cooperation effect.     

Theoretical study of activation Fe–O bond of FeO by CO in the gas phase

The entire reaction mechanism for the gas phase CO–CO₂ conversion by FeO⁺ is discussed by means of the density functional theory and the intrinsic reaction coordinate approach. The calculated results have strongly indicated that the reaction of is a spin-forbidden reaction between the quartet and the sextet potential energy surfaces (PESs). There is a crossing point between the quartet and the sextet potential energy surfaces which may play a significant role in this reaction, by which the activation energy can be decreased from −15.1 to −56.4 kJ mol⁻¹ at the reaction system.     

Phase equilibria and crystal structure of the solid solution LaFe1−xNixO3−δ (0 ≤ x ≤ 1)

Phase equilibria in the LaFeO₃–“LaNiO₃” were studied at 1100 °C in air. The samples were synthesized by standard ceramic and/or solution route via nitrate or citrate precursors. According to the results of XRD it was found that the homogeneity ranges of LaFe_1−xNi_xO_3−δ solid solution lay within 0.0 ≤ x ≤ 0.4 (sp.gr. Pbnm) and 0.6 ≤ x ≤ 0.8 (sp.gr. ). The structural parameters (bond lengths, atom coordinates) for the single-phase samples were refined using Rietveld analysis. The unit cell parameters versus LaFe_1−xNi_xO_3−δ composition are presented.     

New regularities and an equation of state for liquids

Three regularities have been introduced for liquids (T < T_C and ρ > ρ_C) based on average potential energy. The experimental data have been used to show the validity of the regularities. First, there exists near-linearity relation between and ρ for all isotherms of a liquid, where P_i and ρ are internal pressure and density, respectively. Second, changes linearly with ρ for each isotherm of any liquid, where Z and V_m are compressibility factor and molar volume, respectively. Third, a new regularity using the definition of bulk modulus and our new equation of state between reduced bulk modulus and density has been introduced, that is versus ρ must be linear for all isotherms of a liquid where B_r is the reduced bulk modulus.

A new equation of state has been also derived. The density of some liquids in the extensive ranges of temperature and pressure has been calculated using the new equation of state. The densities calculated from this equation agree with experiment to better than 0.3%. The new equation of state can predict internal pressure, thermal expansion coefficient, and isothermal compressibility of liquids within experimental error.     

Second-sphere coordination in hexaamminecobalt(III) salt with organic sulphonate anion: Synthesis, characterisation and X-ray crystal structure of [Co(NH3)6](CH3SO3)3

Reaction of hexaamminecobalt(III) chloride with the silver salt of methanesulphonic acid in aqueous medium (1:3 molar ratio) forms hexaamminecobalt(III) methanesulphonate, [Co(NH₃)₆](CH₃SO₃)₃, in high yield. This cobalt(III) complex has been characterized by spectroscopic techniques (UV/visible, IR and NMR) and its solubility product determined. The X-ray crystal structure shows that the [Co(NH₃)₆]³⁺ cations interact at the second sphere by sharing edges with the anions, via N–H  O hydrogen bonds. The structure is related to that of [Co(NH₃)₆]Cl(CH₃SO₃)₂, but is modified to accommodate additional anions in place of Cl⁻.     

QSAR study on N-containing corrosion inhibitors: Quantum chemical approach assisted by topological index

In this paper, QSAR study on N-containing corrosion inhibitors has been made using quantum chemical approach assisted by a novel topological index (). Two models were obtained and their efficiency was examined using statistics. The results indicate that inhibition efficiencies relate to some parameters of corrosion inhibitors, such as E_homo, polarizability, Dipole, frontier orbital charge density, the interaction mode between inhibitors and metal surface (feedback donor–acceptor coordination bonds), (steric hindrance of molecules). Predicted values are consistent with the experimental ones on the whole. The residuals range within the experimental error. So the models can be used to predict inhibition efficiencies of the same type molecules.     

Rate constants of the O(D) reactions with N2, O2, N2O, and H2O at 295 K

Using a technique of laser flash photolysis coupled with vacuum ultraviolet laser-induced fluorescence spectroscopy, the rate coefficients of O(¹D) reactions with N₂, O₂, N₂O, and H₂O at 295 ± 2 K have been determined to be , k_O2=(4.06±0.24)×10^-11, k_N2O=(1.35±0.08)×10^-10 and . The quoted uncertainties include estimated errors and are the 95% confidence level. The k_N2 and k_N2O values obtained are larger than the current NASA/JPL recommendations by 26% and 16%, respectively, although they are still within the error limits associated with the recommendations.     

Crystal structure, phase transition and thermal behaviour of dabcodiium hexaaquacopper(II) bis(sulfate), (C6H14N2)[Cu(H2O)6](SO4)2

A new organically templated metal sulfate has been synthesized and characterized. At room temperature, dabcodiium hexaaquacopper(II) bis(sulfate), (C₆H₁₄N₂)[Cu(H₂O)₆](SO₄)₂ crystallizes in the monoclinic symmetry (space group P2₁/n) with the following unit cell parameters: a = 6.9533(2), b = 12.5568(2), c = 9.9434(2) Å; β = 90.526(1)° and Z = 2. Its crystal structure is built from isolated [Cu(H₂O)₆]²⁺, and disordered ions linked together by a hydrogen-bonding network. The title compound undergoes a reversible phase transition of the first-order type at 265.7/281.8 K on heating–cooling runs. Below the phase transition temperature, the structure is fully ordered.     

Linking the loading dependence of the Maxwell–Stefan diffusivity of linear alkanes in zeolites with the thermodynamic correction factor

Molecular dynamics simulations have been carried out to determine the Maxwell–Stefan diffusivity Đ of C1–C4 linear alkanes for a range of molecular loadings, q, in AFI, MOR, MTW, and MFI zeolites. Configurational-Bias Monte Carlo simulations were used to determine the thermodynamic correction factor, Γ ≡ ∂ ln f/∂ ln q. For diffusion in the large 1D pores of AFI, Đ is proportional to 1/Γ. In other zeolite topologies with smaller pore sizes, though such a direct proportionality is not observed, the Đ–q dependence appears to be closely linked to the 1/Γ–q characteristics, especially when the latter exhibits strong inflection.     

Mechanical stability and transport properties of the Sn-promoted SrCo0.8Fe0.2O3−δ ceramic membrane

In this article, the phase compositions, thermal, mechanical and transport properties of both the SrCo_0.8Fe_0.2O_3−δ (SCF) and the SrCo_0.8Fe_0.1Sn_0.1O_3−δ (SSCF) ceramic membranes were investigated systematically. As compared with the SCF membrane, the SSCF one had a more promoted thermal shock resistance, which related to its small thermal expansion coefficient between them and an enhanced composite structure for it. For the SCF membrane, a permeation rate of 1.9 × 10⁻⁶ mol cm⁻² s⁻¹ was obtained at 1000 °C and under the oxygen partial pressure gradient of P_O2 (h)/P_O2 (l) = 0.209 atm/0.012 atm; however, the permeation rate was 2.5 × 10⁻⁶ mol cm⁻² s⁻¹ for the SSCF one in the same measuring condition. In addition, both peak values of total electrical conductivity (σ_e) for SSCF sample appeared with increasing temperature. The second peak value of σ_e for SSCF one was regarded as the contribution from its minor phase, which appeared with the mixed conducting behavior resulting from partly Co-dissolving into its lattice.     

A new polar supramolecular 3D framework [Zn(pyz)(H2O)4]pht

A new Zn(II) complex, [Zn(pyz)(H₂O)₄]pht (1) (pyz=pyrazine; pht=1,2-benzenedicarboxylate) has been hydrothermally synthesized and characterized. Complex 1 features a novel polar 3D framework with a 1D polycationic chain , between which pht²⁻ dianions are encapsulated via the supramolecular interaction. Its powder SHG is of about three times as large as that of KH₂PO₄.     

Infrared intensities of liquids XXV: Dielectric constants, molar polarizabilities and integrated intensities of liquid toluene at 25 °C between 4800 and 400 cm

The main purpose of this paper is to present accurate infrared integrated intensities of liquid toluene, C₆H₅CH₃, at 25 °C. Also presented are the decadic molar absorption coefficients, E_m, the real and imaginary dielectric constants, ε′ and ε″, and the real and imaginary molar polarizabilities, ^′_m and ^″_m. Integrated intensities were determined as C_j, the area under bands in the spectrum, for all bands between 4800 and 440 cm⁻¹. The contributions from the different bands were separated by fitting the spectrum with classical damped harmonic oscillator bands. The uncertainties in the integrated intensities of most bands are estimated to be 5–10%, with the uncertainties in very weak bands and in shoulders possibly up to 100%. The intensity that should be assigned to the fundamentals is more difficult to estimate due to Fermi resonance with overtone and combination bands, and a best estimate is given. The integrated intensities of the fundamental vibrations and the corresponding transition dipole moments are summarized and are compared with literature values for the gas.     

A fracture criterion of rubber-like materials under plane stress conditions

In this work, we attempt to derive a fracture criterion for filled and unfilled elastomer vulcanizates and thermoplastics from a set of experimental data. Firstly, fracture criteria reported in the literature have been applied to experimental data obtained from tests including various loading modes (simple tension, equal biaxial tension and biaxial tension) and performed on four materials: a natural rubber (NR), a styrene butadiene rubber (SBR), a polyurethane (PU) and a thermoplastic elastomer (TPE).

Then, a new failure criterion based on an equivalent elongation concept is proposed. This equivalent elongation seems to be linearly dependent on a given biaxiality ratio n=(ln(λ_2b)/ln(λ_1b)), which leads to expressing the principal elongations at break as functions of both the biaxiality n and two experimental parameters. Quite good agreement is highlighted when comparing the failure experimental data with the proposed criterion for the tested elastomers.     

On the 6Πu state of Na2

The 6¹Π_u state of sodium dimer has been observed up to v = 53 in excitation spectra of the system, recorded by polarisation labelling spectroscopy technique. The Dunham coefficients are derived and the potential energy curve constructed by the inverted perturbation approach method. Equilibrium constants for the 6¹Π_u state of Na₂ are: T_e = 35446.06 ± 0.04 cm⁻¹ (with respect to the minimum of the electronic ground state), Y₁₀ = 111.388 ± 0.019 cm⁻¹, Y₀₁ = 0.112122 ± 0.000017 cm⁻¹.     

The 1B1, 1B2, 1A1, 1A2, 3A′(2B2), and 2A1 states of the 1,1-difluoromethane ion studied using multiconfiguration second-order perturbation theory

The 1²B₁(X²B₁), 1²B₂, 1²A₁, 1²A₂, 2²B₂, and 2²A₁ states of the ion were studied using CASPT2 and CASSCF methods. Calculations suggest that one should consider the 3²A′ state instead of 2²B₂. The CASPT2 T₀ calculations predict the energy ordering of 1²B₁(X²B₁), 1²B₂, 1²A₁, 1²A₂, 3²A′, and 2²A₁, which is in line with the experimental results by Pradeep and Shirley. The CASPT2 T₀ values for the 1²B₂, 1²A₂, 3²A′, and 2²A₁ states are close to the experimental values. The F-loss and H-loss dissociation processes were studied at the CASPT2//CASSCF level. The energy levels of low-lying states of are compared.