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In this work, excited-state intramolecular single and double proton transfer mechanisms for 2,5-bis(benzoxazol-2-yl)thiophene-3,4-diol were investigated using time-dependent density functional theory (TDDFT) method for the first time. Our calculations showed that the intramolecular hydrogen bond N⋯H O is strengthened in the excited state, which provides a driving force to effectively facilitate the proton transfer process. The constructed potential energy surface of the excited state demonstrated that the double proton transfer reaction occurs more readily in both dynamics and thermodynamics aspects, and it is implemented by simultaneous double proton transfer, or successive single transfers. Furthermore, the assignments of multiple fluorescence bands in experiment were confirmed by fluorescence spectral simulation. The calculated emission spectra indicated that the experimental fluorescence maxima at 475 nm should be attributed to normal Stokes shifted emission; the large Stokes shifted fluorescence with peaks at 550 nm originates from the double proton transfer phototautomer emission, and the experimentally observed shoulder peak at ∼493 nm results from the excited state single proton transfer tautomer. [ABSTRACT FROM AUTHOR]

The traditional periodic diagram method is primarily used to solve ground motion coherence coefficients. However, in this method, power spectra need to be artificially smoothed, which will result in an abhorrent situation. To solve this key problem, this study uses the dynamic centrifuge model test results with a circular tunnel completed by Schofield Centre (University of Cambridge) as the basic data. The multidimensional autoregressive (AR) model is used to replace the periodic diagram method for computation, and its rationality is evaluated and verified from many perspectives. The difference between the results of the two methods under the condition of tunnel sites in multiple dimensions is discussed from the perspectives of the reconstruction effect, coherence coefficient, and the site amplification effect of records. The results are as follows: The multidimensional AR model can realize the accurate reconstruction of strong motion acceleration records. The coherence coefficient calculated by the AR model is generally smoother than that calculated by the periodic diagram method, which is conducive to fitting and inducing the parameters of empirical models in subsequent research. Under EQ1–EQ4, the ground motion amplification coefficient of each vibration mode first decreases and then increases from the base to the surface. The AR model is more effective than the periodic diagram method in reflecting the importance of the influence of higher-order modes on site amplification. • The coherence function and site amplification effect are calculated by autoregressive model. • The amplification effect in tunnel site with depth is revealed. • The advantages and disadvantages of autoregressive model and periodic diagram method are compared in different aspects. [ABSTRACT FROM AUTHOR]

Abstract: The structural and electronic properties of the wurtzite ZnxCd1−xS and (ZnxCd1−x)(SexS1−x) alloys are calculated using density functional theory calculations with HSE06 hybrid exchange-correlation functional. Special quasirandom structures are used to describe the disordered alloys, for x = 0.125, 0.25, 0.375, 0.5, 0.625, 0.75 and 0.875, respectively. Our calculations reveal that ZnxCd1−xS alloy with the appropriate Zn doping concentration not only causes the elevation of the conduction band minimum energy, but also increase the mobility of photogenerated holes and electrons, which well explains the high photocatalytic activity and stability of Zn0.2Cd0.8S alloy under a long-term light irradiation. Compared with ZnxCd1−xS alloy, (ZnxCd1−x)(SexS1−x) alloy holds greater potential to simultaneously meet band gap, band edge, and mobility criteria for water splitting. Theoretical results predict that (ZnxCd1−x)(SexS1−x) alloy with the ZnSe concentration in the range from 0.38 to 0.75 could be a more promising candidate than Zn0.2Cd0.8S alloy for photoelectrochemical hydrogen production through water splitting. [Copyright &y& Elsevier]