Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocataly...Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.展开更多
In this paper we study the existence and stability of two-dimensional discrete gap breathers in a two-dimensional diatomic face-centered square lattice consisting of alternating light and heavy atoms, with on-site pot...In this paper we study the existence and stability of two-dimensional discrete gap breathers in a two-dimensional diatomic face-centered square lattice consisting of alternating light and heavy atoms, with on-site potential and coupling potential. This study is focused on two-dimensional breathers with their frequency in the gap that separates the acoustic and optical bands of the phonon spectrum. We demonstrate the possibility of the existence of two-dimensional gap breathers by using a numerical method. Six types of two-dimensional gap breathers are obtained, i.e., symmetric, mirror-symmetric and asymmetric, whether the center of the breather is on a light or a heavy atom. The difference between one-dimensional discrete gap breathers and two-dimensional discrete gap breathers is also discussed. We use Aubry＇s theory to analyze the stability of discrete gap breathers in the two-dimensional diatomic face-centered square lattice.展开更多
Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2（0001）are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic（fee）str...Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2（0001）are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic（fee）structure of Sn surface is obtained.Superconductivity is also detected on the fcc-Sn（111）surface,and the size of superconducting gap on the Sn surface is nearly the same as that on the superconducting substrate.Furthermore,phase transition occurs from fcc-Sn（111）toβ-Sn（001）by keeping the sample at room temperature for a certain time.Due to the strain relaxation on theβ-Sn islands,both the in-plane unit cell and out-of-plane structures distort,and the height of surface atoms varies periodically to form a universal ripple structure.展开更多
The dynamical progresses involved in ultra-short laser pulse ablation of face-centered cubic metals under stress confinement condition are described completely using molecular dynamics method. The laser beam absorptio...The dynamical progresses involved in ultra-short laser pulse ablation of face-centered cubic metals under stress confinement condition are described completely using molecular dynamics method. The laser beam absorption and thermal energy turning into kinetics energy of. atoms are taken into account to give a detailed picture of laser metal interaction. Superheating phenomenon is observed, and the phase change from solid to liquid is characterized by a destroyed atom configuration and a decreased number density. The steep velocity gradients are found in the systems of Cu and Ni after pulse in consequence of located heating and exponential decrease of fluences following the Lambert-Beer expression. The shock wave velocities are predicted to be about 5 000 m/s in Cu and 7 200 m/s in Ni. The higher ablation rates are obtained from simulations compared with experimental data as a result of a well-defined crystalline surface irradiated by a single pulse. Simulation results show that the main mechanisms of ablation are evaporation and thermoelastic stress due to located heating.展开更多
基金the support from the National Natural Science Foundation of China(22272121,21972107)the National Key Research and Development program of China(2021YFB4001200)。
文摘Metastable nanostructured electrocatalyst with a completely different surface environment compared to conventional phase-based electrocatalyst often shows distinctive catalytic property.Although Ru-based electrocatalysts have been widely investigated toward hydrogen oxidation reaction(HOR)under alkaline electrolytes,these studies are mostly limited to conventional hexagonal-close-packed(hcp)phase,mainly arising from the lack of sufficient synthesis strategies.In this study,we report the precise synthesis of metastable binary RuW alloy with face-centered-cubic(fcc)phase.We find that the introduction of W can serve as fcc phase seeds and reduce the formation energy of metastable fcc-RuW alloy.Impressively,fcc-RuW exhibits remarkable alkaline HOR performance and stability with the activity of 0.67 mA cm_(Ru)^(-2)which is almost five and three times higher than that of hcp-Ru and commercial Pt/C,respectively,which is attributed to the optimized binding strength of adsorbed hydroxide intermediate derived from tailored electronic structure through W doping and phase engineering.Moreover,this strategy can also be applied to synthesize other metastable fcc-RuCr and fcc-RuMo alloys with enhanced HOR performances.
基金Project supported by the National Natural Science Foundation of China (Grant No 10574011)the Foundation for Researching Group by Beijing Normal University
文摘In this paper we study the existence and stability of two-dimensional discrete gap breathers in a two-dimensional diatomic face-centered square lattice consisting of alternating light and heavy atoms, with on-site potential and coupling potential. This study is focused on two-dimensional breathers with their frequency in the gap that separates the acoustic and optical bands of the phonon spectrum. We demonstrate the possibility of the existence of two-dimensional gap breathers by using a numerical method. Six types of two-dimensional gap breathers are obtained, i.e., symmetric, mirror-symmetric and asymmetric, whether the center of the breather is on a light or a heavy atom. The difference between one-dimensional discrete gap breathers and two-dimensional discrete gap breathers is also discussed. We use Aubry＇s theory to analyze the stability of discrete gap breathers in the two-dimensional diatomic face-centered square lattice.
基金Supported by the National Key Research and Development Program of China under Grant Nos 2016YFA0301003 and 2016YFA0300403the National Natural Science Foundation of China under Grant Nos 11521404,11634009,U1632102,11504230,11674222,11574202,11674226,11574201 and U1632272
文摘Surface structures and properties of Sn islands grown on superconducting substrate 2H-NbSe2（0001）are studied using low temperature scanning tunneling microscopy or spectroscopy.The pure face-centered cubic（fee）structure of Sn surface is obtained.Superconductivity is also detected on the fcc-Sn（111）surface,and the size of superconducting gap on the Sn surface is nearly the same as that on the superconducting substrate.Furthermore,phase transition occurs from fcc-Sn（111）toβ-Sn（001）by keeping the sample at room temperature for a certain time.Due to the strain relaxation on theβ-Sn islands,both the in-plane unit cell and out-of-plane structures distort,and the height of surface atoms varies periodically to form a universal ripple structure.
基金the Ministerial Level Advanced Research Foundation (ABAQ440261)
文摘The dynamical progresses involved in ultra-short laser pulse ablation of face-centered cubic metals under stress confinement condition are described completely using molecular dynamics method. The laser beam absorption and thermal energy turning into kinetics energy of. atoms are taken into account to give a detailed picture of laser metal interaction. Superheating phenomenon is observed, and the phase change from solid to liquid is characterized by a destroyed atom configuration and a decreased number density. The steep velocity gradients are found in the systems of Cu and Ni after pulse in consequence of located heating and exponential decrease of fluences following the Lambert-Beer expression. The shock wave velocities are predicted to be about 5 000 m/s in Cu and 7 200 m/s in Ni. The higher ablation rates are obtained from simulations compared with experimental data as a result of a well-defined crystalline surface irradiated by a single pulse. Simulation results show that the main mechanisms of ablation are evaporation and thermoelastic stress due to located heating.
