We reveal the electronic structure in Yb Cd_(2)Sb_(2),a thermoelectric material,by angle-resolved photoemission spectroscopy(ARPES)and time-resolved ARPES(tr ARPES).Specifically,three bulk bands at the vicinity of the...We reveal the electronic structure in Yb Cd_(2)Sb_(2),a thermoelectric material,by angle-resolved photoemission spectroscopy(ARPES)and time-resolved ARPES(tr ARPES).Specifically,three bulk bands at the vicinity of the Fermi level are evidenced near the Brillouin zone center,consistent with the density functional theory(DFT)calculation.It is interesting that the spin-unpolarized bulk bands respond unexpectedly to right-and left-handed circularly polarized probe.In addition,a hole band of surface states,which is not sensitive to the polarization of the probe beam and is not expected from the DFT calculation,is identified.We find that the non-equilibrium quasiparticle recovery rate is much smaller in the surface states than that of the bulk states.Our results demonstrate that the surface states can be distinguished from the bulk ones from a view of time scale in the nonequilibrium physics.展开更多
The electronic properties of FeS 2 (100) surface were studied by using a density functional theory(DFT) method. The very stable (100) surface does not give any significant geometric relaxation and can be regarded as a...The electronic properties of FeS 2 (100) surface were studied by using a density functional theory(DFT) method. The very stable (100) surface does not give any significant geometric relaxation and can be regarded as a simple termination of the bulk structure along a plane of cleaved Fe S bonds. The electronic structure of FeS 2 (100) surface is characterized by surface states in its forbidden zone. The highest occupied and the lowest unoccupied states localize at surface Fe sites. Fe sites are energetically favored over S 2 sites for redox interaction with electron donor or acceptor species on (100) surface.展开更多
Kinetic investigations including quasi-classical trajectory and canonical unified statistical theory method calculations are carried out on a potential energy surface for the hydrogen-abstraction reaction from methane...Kinetic investigations including quasi-classical trajectory and canonical unified statistical theory method calculations are carried out on a potential energy surface for the hydrogen-abstraction reaction from methane by atom O(^3P).The surface is constructed using a modified Shepard interpolation method.The ab initio calculations are performed at the CCSD(T)level.Taking account of the contribution of inner core electrons to electronic correlation interaction in ab initio electronic structure calculations,modified optimized aug-cc-pCVQZ basis sets are applied to the all-electrons calculations.On this potential energy surface,the triplet oxygen atom attacks methane in a near-collinear H-CH3 direction to form a saddle point with barrier height of 13.55 kcal/mol,which plays a key role in the kinetics of the title reaction.For the temperature range of 298-2500 K,our calculated thermal rate constants for the O(^3P)+CH4→OH+CH3 reaction show good agreement with relevant experimental data.This work provides detailed mechanism of this gas-phase reaction and a theoretical guidance for methane combustion.展开更多
基金support from the National Natural Science Foundation of China(Grant No.11974243)support from the National Natural Science Foundation of China(Grant No.11521404)+1 种基金additional support from a Shanghai talent programsupport by the Natural Science Foundation of Shanghai,China(Grant No.17ZR1443300)。
文摘We reveal the electronic structure in Yb Cd_(2)Sb_(2),a thermoelectric material,by angle-resolved photoemission spectroscopy(ARPES)and time-resolved ARPES(tr ARPES).Specifically,three bulk bands at the vicinity of the Fermi level are evidenced near the Brillouin zone center,consistent with the density functional theory(DFT)calculation.It is interesting that the spin-unpolarized bulk bands respond unexpectedly to right-and left-handed circularly polarized probe.In addition,a hole band of surface states,which is not sensitive to the polarization of the probe beam and is not expected from the DFT calculation,is identified.We find that the non-equilibrium quasiparticle recovery rate is much smaller in the surface states than that of the bulk states.Our results demonstrate that the surface states can be distinguished from the bulk ones from a view of time scale in the nonequilibrium physics.
文摘The electronic properties of FeS 2 (100) surface were studied by using a density functional theory(DFT) method. The very stable (100) surface does not give any significant geometric relaxation and can be regarded as a simple termination of the bulk structure along a plane of cleaved Fe S bonds. The electronic structure of FeS 2 (100) surface is characterized by surface states in its forbidden zone. The highest occupied and the lowest unoccupied states localize at surface Fe sites. Fe sites are energetically favored over S 2 sites for redox interaction with electron donor or acceptor species on (100) surface.
基金Project supported by the National Natural Science Foundation of China(Grant No.51574016)and completed while the author was in residence at UNSW,Australia supported by the International Cooperation Training Program for Innovative Talents of USTB.
文摘Kinetic investigations including quasi-classical trajectory and canonical unified statistical theory method calculations are carried out on a potential energy surface for the hydrogen-abstraction reaction from methane by atom O(^3P).The surface is constructed using a modified Shepard interpolation method.The ab initio calculations are performed at the CCSD(T)level.Taking account of the contribution of inner core electrons to electronic correlation interaction in ab initio electronic structure calculations,modified optimized aug-cc-pCVQZ basis sets are applied to the all-electrons calculations.On this potential energy surface,the triplet oxygen atom attacks methane in a near-collinear H-CH3 direction to form a saddle point with barrier height of 13.55 kcal/mol,which plays a key role in the kinetics of the title reaction.For the temperature range of 298-2500 K,our calculated thermal rate constants for the O(^3P)+CH4→OH+CH3 reaction show good agreement with relevant experimental data.This work provides detailed mechanism of this gas-phase reaction and a theoretical guidance for methane combustion.
