Polarizable interaction potential for water from coupled cluster calculations. II. Applications to dimer spectra, virial coefficients, and simulations of liquid water

The six-dimensional CC-pol interaction potential for the water dimer was used to predict properties of the dimer and of liquid water, in the latter case after being supplemented by a nonadditive potential. All the results were obtained purely from first principles, i.e., without any fitting to experimental data. Calculations of the vibration-rotation-tunneling levels of (H(2)O)(2) and (D(2)O)(2), a very sensitive test of the potential surface, gave results in good agreement with experimental high-resolution spectra. Also the virial coefficients and properties of liquid water agree well with measured values. The present model performs better than published force fields for water in a simultaneous reproduction of experimental data for dimer spectra, virials, and properties of the liquid.     

Transformation properties of many-electron wave functions with special attention to the relation between pair-correlated DODS and configuration interaction

A method is presented that leads to a simple derivation of the explicit relation between pair-correlated DODS schemes (e.g., the alternant molecular orbital method and the extended valence bond method) and configuration interaction. This result is based on a reduction formula for the representations of the general linear group, GL(m), carried by the N-electron function space. Generally, this paper deals with the effect of “partitioned” orbital transformations on states with “local” permutation symmetry.     

Synthesis and characterization of fully biobased poly(propylene succinate‐ran‐propylene adipate). Analysis of the architecture‐dependent physicochemical behavior

Fully biobased aliphatic random poly(1,3‐propylene succinate‐ran‐1,3‐propylene adipate) (PPSA) copolyesters with high molar mass were synthesized with different macromolecular architectures based on various succinic acid/adipic acid (SA/AA) molar ratio, by transesterification in melt. Titanium (IV) isopropoxide was used as an effective catalyst. All synthesized copolyesters were fully characterized by different chemical and physicochemical techniques including NMR, size exclusion chromatography, FTIR, wide angle X‐ray scattering, differential scanning calorimetry, and thermogravimetric analysis. The final copolyesters molar compositions were identical to the feed ones. The different sequences based on succinate and adipate segments were randomly distributed along the chains. All the corresponding copolyesters showed an excellent thermal stability with a degradation onset temperature higher than 290 °C, which increased with the adipate content. According to their compositions and architectures, PPSA copolyesters can exhibit or not a crystalline phase, at room temperature. T_g of copolyesters decreased with the adipate content due to the decrease in the chains mobility, following the Gordon–Taylor relation. PPSA showed a pseudo eutectic melting behavior characteristic of an isodimorphic character. Finally, PPSA copolyesters were not able to crystallize during the cooling or the second heating run, due to the 1,3‐propanediol chemical structure, which led to amorphous materials with the exception of the polyester based solely on AA. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2738–2748     

Ab initio treatment of the chemical reaction precursor complex Cl(2P)-HF. 2. Bound states and infrared spectrum

Bound energy levels and properties of the Cl(2P)-HF complex were obtained from full three-dimensional (3D) calculations, with the use of the ab initio computed diabatic potential surfaces from the preceding paper and the inclusion of spin-orbit coupling. For a better understanding of the dynamics of this complex we also computed a 2D model in which the HF bond length r was frozen at the vibrationally averaged values r0 and r1 and a 2 + 1D model in which the 3D potentials were averaged over the v(HF) = 0 and v(HF) = 1 vibrational wave functions of free HF. Also 1D calculations were made in which both r and the Cl-HF distance R were frozen. The complex is found to have the linear hydrogen bonded Cl-HF structure, with ground-state quantum numbers J = 3/2 for the overall angular momentum and /omega/ = 3/2 for its projection on the intermolecular axis R. The binding energy is D0 = 432.25 cm(-1) for v(HF) = 0 and D0 = 497.21 cm(-1) for v(HF) = 1. Bending modes with /omega/ = 1/2 and /omega/ = 5/2 are split by the Renner-Teller effect, since the electronic ground state is a degenerate 2pi state. A series of intermolecular (R) stretch modes was identified. Rotational constants and e-f parity splittings were extracted from the levels computed for J = 1/2 to 7/2. The computed red shift of the HF stretch frequency of 64.96 cm(-1) and the 35Cl-37Cl isotope shift of 0.033 cm(-1) are in good agreement with the values of 68.77 and 0.035 cm(-1) obtained from the recent experiment of Merritt et al. (Phys. Chem. Chem. Phys. 2005, 7, 67), after correction for the effect of the He nanodroplet matrix in which they were measured.     

Nonisothermal crystallization behavior of poly(butylene adipate‐co‐terephthalate)/clay nano‐biocomposites

The study of the nonisothermal crystallization behavior of layered silicates micro‐ and nano‐biocomposites based on poly(butylene adipate‐co‐terephthalate) (PBAT), a biodegradable copolyester, has been carried out with different theoretical models. They were applied and developed with the aim to describe and better understand the influence of the layered silicates dispersion on crystallization. The nucleation efficiency of the layered silicates has been demonstrated with the use of the “Modified Avrami model,” thanks to the higher crystallization rate parameter, Z_c, and of the lower crystallization half‐time, t_1/2, compared to the neat matrix. The crystallization activation energies, E_a, calculated from “Kissinger's model” have shown that layered silicates have a negative effect on the crystallite growth process. Thus, these analyses have shown that layered silicates have a double effect on the crystallization process. These two opposites' phenomena depend on the dispersion quality and are more pronounced for the intercalated nano‐biocomposites. © 2007 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 45: 1503–1510, 2007     

Using aggregate fill rate for dynamic scheduling of multi-class systems

For dynamic scheduling of multi-class systems where backorder cost is incurred per unit backordered regardless of the time needed to satisfy backordered demand, the following models are considered: the cost model to minimize the sum of expected average inventory holding and backorder costs and the service model to minimize expected average inventory holding cost under an aggregate fill rate constraint. Use of aggregate fill rate constraint in the service model instead of an individual fill rate constraint for each class is justified by deriving equivalence relations between the considered cost and service models. Based on the numerical investigation that the optimal policy for the cost model is a base-stock policy with switching curves and fixed base-stock levels, an alternative service model is considered over the class of base-stock controlled dynamic scheduling policies to minimize the total inventory (base-stock) investment under an aggregate fill rate constraint. The policy that solves this alternative model is proposed as an approximation of the optimal policy of the original cost and the equivalent service models. Very accurate heuristics are devised to approximate the proposed policy for given base-stock levels. Comparison with base-stock controlled First Come First Served (FCFS) and Longest Queue (LQ) policies and an extension of LQ policy (Δ policy) shows that the proposed policy performs much better to solve the service models under consideration, especially when the traffic intensity is high.     

Radiation emission from the ＂Rhodotron-TT200＂ cavity

In this paper, the X-rays emitted from the Rhodotron-TT200 cavity have been studied in depth. We found that the Bremsstrahlung interaction is the only contribution of X-ray generation important to safety. The X-ray dose rate in the Rhodotron vault is calculated for normal conditions based on MCNP4C results. The presented calculation shows good agreement with the experimental measurements, which consequently confirms the reliability of the calculation for use in shielding design and other safety aspects.     

On the role of the magnetic dipolar interaction in cold and ultracold collisions: numerical and analytical results for NH(3Σ−) + NH(3Σ−)

We present a detailed analysis of the role of the magnetic dipole-dipole interaction in cold and ultracold collisions. We focus on collisions between magnetically trapped NH molecules, but the theory is general for any two paramagnetic species for which the electronic spin and its space-fixed projection are (approximately) good quantum numbers. It is shown that dipolar spin relaxation is directly associated with magnetic-dipole induced avoided crossings that occur between different adiabatic potential curves. For a given collision energy and magnetic field strength, the cross-section contributions from different scattering channels depend strongly on whether or not the corresponding avoided crossings are energetically accessible. We find that the crossings become lower in energy as the magnetic field decreases, so that higher partial-wave scattering becomes increasingly important below a certain magnetic field strength. In addition, we derive analytical cross-section expressions for dipolar spin relaxation based on the Born approximation and distorted-wave Born approximation. The validity regions of these analytical expressions are determined by comparison with the NH + NH cross sections obtained from full coupled-channel calculations. We find that the Born approximation is accurate over a wide range of energies and field strengths, but breaks down at high energies and high magnetic fields. The analytical distorted-wave Born approximation gives more accurate results in the case of s-wave scattering, but shows some significant discrepancies for the higher partial-wave channels. We thus conclude that the Born approximation gives generally more meaningful results than the distorted-wave Born approximation at the collision energies and fields considered in this work.