The finite-temperature density-functional theory and quasiharmonic lattice dynamics are used to calculate the Gibbs free energy and quasiharmonic phonons of the hexagonal-close-packed ͑hcp͒ and omega ͑͒ crystal structures for Zr. The hcp phonon dispersions agree with experiment; the phonon dispersions have not been measured yet. From the free energy, the volume thermal expansion coefficients of ␣-Zr are predicted. The calculated volume thermal expansion coefficients for ␣-Zr are in good agreement with the experiment data at T Ͼ 100 K. Our calculated results found that at zero-temperature the lowest-energy phase is not the but the hcp phase. This conclusion is in accordance with the result of Schnell and Albers, but in disagreement with those of Ahuja et al. and Jona and Marcus. The predicted phase boundary of ␣ → is in good agreement with the available experiment; however, other theoretical results are far from the experiment at high temperatures.

Energetic self-healing adhesives have a positive effect on the energy level, mechanical properties, and microcrack healing performance of energetic composite materials (ECMs). However, it is very challenging to design and...

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A nafion film containing cerium phosphate nanotubes was pasted onto a glassy carbon electrode (GCE) to obtain a sensor for hydroquinone (HQ). The morphologies and components of the coating were characterized by transmission electron microscopy, scanning electron microscopy and energy-dispersive spectroscopy. Cyclic voltammetry and differential pulse voltammetry (DPV) showed the specific surface of the electrode to be significantly increased and the electron transfer rate to be accelerated. The modified GCE was applied to the determination of hydroquinone (HQ) via DPV. The oxidation current increases linearly in the 0.23 μM to 16 mM HQ concentration range which is as wide as five orders of magnitude. The limit of detection is 0.12 μM (based on a signal-to-noise ratio of 3), and the sensitivity is 1.41 μA·μM cm. The method was further applied to the simultaneous determination of HQ, catechol and resorcinol. The potentials for the three species are well separated (20, 134, and 572 mV vs SCE). Average recoveries from (spiked) real water samples are between 95.2 and 107.0%, with relative standard deviations of 0.9~2.7% (for n = 3) at three spiking levels. The method was validated by independent assays using HPLC. Graphical abstract ᅟ.

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Using the CCSD(T) method with relativistic correlation consistent basis sets up to cc-pVQZ-PP, the entrance complex, transition state, and exit complex for the endothermic reaction I + H2O → HI + OH have been studied. The vibrational frequencies and the zero-point vibrational energies of the five stationary points for the title reaction are reported and compared with the limited available experimental results. Opposite to the valence isoelectronic F + H2O system, but similar to the Cl + H2O and Br + H2O reactions, the I + H2O reaction is endothermic, in this case by 46 kcal mol(-1). After the zero-point vibrational energy and spin-orbit coupling corrections, the endothermic reaction energy is predicted to be 48 kcal mol(-1), which agrees well with experimental values. For the reverse reaction HI + OH → I + H2O the transition state lies below the reactants, consistent with the experimental negative temperature dependence for the rate constants.

Using the projector augmented wave (PAW) within the Perdew-Burke-Ernzerhof (PBE) form of the generalized gradient approximation (GGA), we investigate the effect of hydrostatic pressure on the structures of zirconium metal at zero temperature. We obtain the [Formula: see text] transition at around 26.8 GPa, which is in excellent agreement with the experimental values. We also find that the ω phase is most stable at 0 K and 0 GPa. This conclusion is supported by first-principles calculations of Schell et al and Jona et al. The elastic constants of ω-Zr under high pressures are calculated for the first time. We find that the compressional and shear wave velocities increase monotonically with increasing pressure and the results are in good agreement with the available experimental data. The pressure dependences of three anisotropies of elastic waves are also presented.