First-principles study on superconductivity of P- and Cl-doped H3_3S

The recent reports on 203 K superconductivity in compressed hydrogen sulfide, H$_3$S, has attracted great interest in sulfur-hydrogen system under high pressure. Here, we investigated the superconductivity of P-doped and Cl-doped H$_3$S using the first-principles calculations based on the supercell method, which gives more reliable results on the superconductivity in doped systems than the calculations based on the virtual crystal approximation reported earlier. The superconducting critical temperature is increased from 189 to 212 K at 200 GPa in a cubic $Im\bar{3}m$ phase by the 6.25 % P doping, whereas it is decreased to 161 K by the 6.25 % Cl doping. Although the Cl doping weakens the superconductivity, it causes the $Im\bar{3}m$ phase to be stabilized in a lower pressure region than that in the non-doped H$_3$S.Comment: 7 pages, 5 figures, 5 tables, submitted to Physical Review

Structural analysis of zirconium oxynitride/water interface using neural network potential

Zr oxides with oxygen-nitrogen substitutions and oxygen vacancies are promising candidates to replace Pt as electrocatalyst for the oxygen reduction reaction. To understand the microscopic structure of the catalyst/water interface, many nanosecond-long molecular dynamics simulations were performed using the interatomic force field constructed by machine learning the ab initio calculations. A defective Zr$_7$O$_8$N$_4$/H$_2$O interface model was simulated and compared with a pristine ZrO$_2$/H$_2$O interface model. Water was found to be adsorbed on the surface partly as a H$_2$O molecule or as dissociated components, OH and H, on both surfaces. On the pristine ZrO$_2$ surface, H$_2$O molecules show a monolayer adsorption structure and adsorb on all Zr atoms with equal probability. On defective Zr$_7$O$_8$N$_4$ surface, however, H$_2$O molecules show a bilayer adsorption structure and do not adsorb on the oxygen vacancies but only on some of the surrounding Zr atoms. The total number of the molecular and dissociative adsorptions are almost the same on both surfaces, but a larger number are dissociatively adsorbed on the pristine surface. Possible implications for the catalytic behaviour are discussed.Comment: 27 pages, 6 figure

General Rule and Materials Design of Negative Effective U System for High-T_c Superconductivity

Based on the microscopic mechanisms of (1) charge-excitation-induced negative effective U in s^1 or d^9 electronic configurations, and (2) exchange-correlation-induced negative effective U in d^4 or d^6 electronic configurations, we propose a general rule and materials design of negative effective U system in itinerant (ionic and metallic) system for the realization of high-T_c superconductors. We design a T_c-enhancing layer (or clusters) of charge-excitation-induced negative effective $U$ connecting the superconducting layers for the realistic systems.Comment: 11 pages, 1 figures, 2 tables, APEX in printin

Expansion of retinal nerve fiber bundle narrowing in glaucoma: An adaptive optics scanning laser ophthalmoscopy study

Purpose: To investigate longitudinal changes in the retinal nerve fiber bundle in eyes with primary open angle glaucoma using adaptive optics scanning laser ophthalmoscopy. Methods: A prospective observational case series. Fourteen eyes from 12 patients with primary open angle glaucoma that exhibited retinal nerve fiber layer defects on fundus photography were imaged with adaptive optics scanning laser ophthalmoscopy over time. Results: The expansion of retinal nerve fiber bundle narrowing was observed on adaptive optics scanning laser ophthalmoscopy in 8 eyes (57.1%) over a period of 1.44 ± 0.42 years. Retinal nerve fiber bundle narrowing expanded horizontally in 2 eyes and vertically in 6 eyes. In 3 eyes, changes in the retinal nerve fiber layer were only detectable on adaptive optics scanning laser ophthalmoscopy images. Conclusions and Importance: The expansion of retinal nerve fiber bundle narrowing was observed using adaptive optics scanning laser ophthalmoscopy. Accordingly, this tool may be a useful tool for detecting glaucoma-related changes in retinal nerve fibers in a short time