Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, the...Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.展开更多
Density functional theory calculations corrected by on-site Coulomb interactions were carried out o study the structures of polar CeO2 （100） surfaces as well as activities during catalytic CO oxidation. The stabilit...Density functional theory calculations corrected by on-site Coulomb interactions were carried out o study the structures of polar CeO2 （100） surfaces as well as activities during catalytic CO oxidation. The stabilities of various CeO2 （100） termination structures are discussed, and calculated energetics are presented. The most stable Ce〇2 （100） surface was obtained by removing half the outermost full layer of oxygen and the surface stability was found to decrease as the exposed oxygen concentration was increased. Assessing the reaction pathways leading to different final products during CO oxidation over the most stable CeO2 （100） surface, we determined that the formation of carbonate species competed with CO2 desorption. However, during CO oxidation on the less stable CeO2 （100） surfaces having more exposed oxygen, the CO is evidently able to react with surface oxygen, leading to CO2 formation and desorption. The calculation results and electronic analyses reported herein also indicate that the characteristic Ce 4/ orbitals are directly involved in deter-mining the surface stabilities and reactivities.展开更多
The interaction of atomic oxygen with the clean Cu（100） surface has been studied by means of cluster and periodic slab models density functional theory in the present paper. The Cu（4,9,4） cluster and a three-layer...The interaction of atomic oxygen with the clean Cu（100） surface has been studied by means of cluster and periodic slab models density functional theory in the present paper. The Cu（4,9,4） cluster and a three-layer slab with c（2×2） structure are used to model the perfect Cn（100） surface. Three possible adsorption sites, top, bridge and hollow site, were considered in the calculations. The predicted results show that the hollow site is the prefer site for atomic oxygen adsorbed on Cu（100） surface energetically. This is in good agreement with the experiment. The calculated binding energies are respective 2.014, 3.154 and 3.942 eV for top, bridge and hollow sites at mPW1PW91/LanL2dz level for the cluster model. The geometry of Cu（100） surface has also been optimized theoretically with various density functional rnethods and the results show that the prediction from the B3PW91/LanL2dz and mPWlPW91/LanL2dz reproduce the experimental observation. The frontier molecular orbitals and partial density of states analysis show that the electron transfer from the d orbital of substrate to the p orbital of the surface oxygen atom.展开更多
文摘Pyrite （FeS2） bulk and （100） surface properties and the oxygen adsorption on the surface were studied by using density functional theory methods. The results show that in the formation of FeS2 （100） surface, there exists a process of electron transfer from Fe dangling bond to S dangling bond. In this situation, surface Fe and S atoms have more ionic properties. Both Fe2+ and S2- have high electrochemistry reduction activity, which is the base for oxygen adsorption. From the viewpoint of adsorption energy, the parallel form oxygen adsorption is in preference. The result also shows that the state of oxygen absorbed on FeS2 surface acts as peroxides rather than O2.
基金supported the National Natural Science Foundation of China(21421004,21573067)~~
文摘Density functional theory calculations corrected by on-site Coulomb interactions were carried out o study the structures of polar CeO2 （100） surfaces as well as activities during catalytic CO oxidation. The stabilities of various CeO2 （100） termination structures are discussed, and calculated energetics are presented. The most stable Ce〇2 （100） surface was obtained by removing half the outermost full layer of oxygen and the surface stability was found to decrease as the exposed oxygen concentration was increased. Assessing the reaction pathways leading to different final products during CO oxidation over the most stable CeO2 （100） surface, we determined that the formation of carbonate species competed with CO2 desorption. However, during CO oxidation on the less stable CeO2 （100） surfaces having more exposed oxygen, the CO is evidently able to react with surface oxygen, leading to CO2 formation and desorption. The calculation results and electronic analyses reported herein also indicate that the characteristic Ce 4/ orbitals are directly involved in deter-mining the surface stabilities and reactivities.
基金This work was supported by National Natural Science Foundation of China （NSFC No. 20273013） and Pujian Provincial Department of Education （No. JA03020）
文摘The interaction of atomic oxygen with the clean Cu（100） surface has been studied by means of cluster and periodic slab models density functional theory in the present paper. The Cu（4,9,4） cluster and a three-layer slab with c（2×2） structure are used to model the perfect Cn（100） surface. Three possible adsorption sites, top, bridge and hollow site, were considered in the calculations. The predicted results show that the hollow site is the prefer site for atomic oxygen adsorbed on Cu（100） surface energetically. This is in good agreement with the experiment. The calculated binding energies are respective 2.014, 3.154 and 3.942 eV for top, bridge and hollow sites at mPW1PW91/LanL2dz level for the cluster model. The geometry of Cu（100） surface has also been optimized theoretically with various density functional rnethods and the results show that the prediction from the B3PW91/LanL2dz and mPWlPW91/LanL2dz reproduce the experimental observation. The frontier molecular orbitals and partial density of states analysis show that the electron transfer from the d orbital of substrate to the p orbital of the surface oxygen atom.
