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Computational screening of organic molecules as redox active species in redox flow batteries
A.L. Solovjov,L.V. Omelchenko 한국물리학회 2016 Current Applied Physics Vol.16 No.9
In general, redox active species with a wide redox window and high solubility are necessary to increase the energy density of redox flow batteries. We employed the following three screening factors aimed at identifying such new redox active materials: oxidation potential, reduction potential, and solvation energy. Of the 106 organic molecule candidates, we managed to obtain five molecules that satisfy the screening criteria, namely, trifluoromethoxy-trifluoromethoxybenzylbenzene, bromo-methoxybenzonitrile, dimethoxy-octafluorobiphenyl, chloro-methoxypyridine, and dimethoxyphenyl-ethanone. The characteristics of each molecule are then examined, which enable us to suggest two promising redox active materials for redox flow batteries: fluoro-methoxybenzonitrile and dimethoxyoctafluorobiphenyl.
A.L. Solovjov,L.V. Omelchenko,R.V. Vovk,O.V. Dobrovolskiy,S.N. Kamchatnaya,D.M. Sergeev 한국물리학회 2016 Current Applied Physics Vol.16 No.9
The influence of the hydrostatic pressure P up to 0.95 GPa on the excess conductivity s0(T) and the pseudogap D*(T) in optimally doped YBa2Cu3O7d single crystals (Tc x 91.1 K at ambient pressure) is investigated by electrical resistivity measurements. A pronounced enhancement of the pseudogap under pressure of dlnD*/dP z 0.32, which is only a factor of 1.12 smaller than in slightly doped single crystals, is revealed for the first time. This implies a somewhat more moderate increase of the coupling strength in optimally doped cuprates with increasing pressure. Simultaneously, the ratio 2D*(Tc)/kBTc z 5 at P ¼ 0 GPa, which is typical for high-temperature superconductors with strong coupling, increases by 16% with increasing pressure. At the same time, the pressure effect on Tc is minor: dTc/dP z þ0.73 K GPa1, whereas dlnr/dP z (17 ± 0.2)% GPa1 is comparable with that in lightly doped YBCO single crystals. This suggests that the mechanisms of the pressure effect on r(T) and Tc are noticeably different. Independently of pressure, near Tc, s0(T) is well described by the Aslamazov-Larkin (3D-AL) and 2D Hikami- Larkin fluctuation theories, exhibiting a 3De2D crossover with increasing temperature. However, the temperature interval Tc < T < T01, in which s0(T) obeys the classical fluctuation theories, is exceptionally narrow (z1.16 K). Nevertheless, a peculiarity at the temperature T01, up to which the wave function phase stiffness in the superconductor is maintained, is clearly observed in the dependence D*(T). Below T01 a fast growth of D*(T) is revealed for the first time. It can be associated with a sudden increase of the superfluid density, ns, that is the density of fluctuating Cooper pairs (short-range phase correlations) forming in the sample when T approaches Tc.
Hannachi E.,Slimani Y.,Almessiere M.A.,Alotaibi S.A.,Omelchenko L.V.,Petrenko E.V.,Kurbanov U.,Ben Azzouz F.,Solovjov A.L.,Baykal A. 한국물리학회 2023 Current Applied Physics Vol.48 No.-
We report the effect of the addition of BaTiO3 and WO3 nanoparticles on the pseudogap and excess conductivity of YBCO polycrystal. The excess conductivity analysis showed that the experimental data of pure and sample added with low amount of WO3 and BaTiO3 were perfectly described by the 2D Maki-Thompson (MT) and 3D Aslamazov-Larkin (AL) models. A sharp decrease in excess conductivity was obtained for samples added with high amount of nanoparticles where the analysis indicated the presence of the AL contribution and Lawrence- Doniach (LD) models. The pseudogap (PG) results showed that the value of Tpair (the temperature at which local pairs are transformed from strongly bound bosons into the fluctuating Cooper pairs) increased from around 117 K for the pure sample to around 187 K for sample co-added with low amount of nanoparticles. The pseudogap Δ*(TG) reduced from 230.9 K (for pure sample) to 223.4 K (for added sample).