We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomi...We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.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
The HCNH and CNH2 adsorption on different coordination sites of Cu（100） was theoretically studied considering the cluster approach. The present calculations show that the bridge site is the most favorite for CNH2 pe...The HCNH and CNH2 adsorption on different coordination sites of Cu（100） was theoretically studied considering the cluster approach. The present calculations show that the bridge site is the most favorite for CNH2 perpendicularly adsorbed on the Cu（100） surface via the C atom. For HCNH absorbed on the Cu（100） surface, the parallel adsorption mode with the C and N atoms nearly directly above the adjacent top sites of Cu（100） surface is the most favored. Both CNH2 and HCNH are strongly bound to the Cu（100） surface with CNH2 which is lightly stable （2.51 kJ·mol^-1）, indicating that both species may be co-adsorbed on the Cu（100） surface.展开更多
The adsorption and reaction of O ＋ CN → OCN on Cu（100） are studied by using density functional theory and cluster model. Cu14 cluster model is used to simulate the surface. The calculated results show that the OCN...The adsorption and reaction of O ＋ CN → OCN on Cu（100） are studied by using density functional theory and cluster model. Cu14 cluster model is used to simulate the surface. The calculated results show that the OCN species with the molecule perpendicular to the surface via N atom （N-down） is more favorable than other adsorption models, and the N-down at the bridge site is the most favorable. For N-down, calculated OCN symmetric and asymmetric stretching frequencies are all blue-shifted compared with the calculated values of free and in good agreement with the experiments. The charge transfer from the surface to the OCN species leads to that the bonding of OCN to the metal surface is largely ionic. The present studies also show that CN with the molecule perpendicular to the surface via C atom （NC-down） at the top site is the most stable. Except NC-down at the top site, the calculated CN stretching frequencies are all red-shifted. With O coadsorbed at the hollow site, the adsorption of NC-down at the next nearest bridge or top site is energetically more favorable than that at the adjacent hollow site. The reaction of O ＋ CN → OCN on Cu（100） has no energy barrier via both Eley-Rideal and Langmuir-Hinshelwood processes.展开更多
The molecular-level identification of a chiral recognition process of phthalocyanine （Pc） was studied on a Cu（100） surface by scanning tunneling microscopy （STM）. STM revealed that a chiral Pc molecule forms a s...The molecular-level identification of a chiral recognition process of phthalocyanine （Pc） was studied on a Cu（100） surface by scanning tunneling microscopy （STM）. STM revealed that a chiral Pc molecule forms a series of metastable dimer configurations with other Pc molecules. Eventually, the Pc molecule recognizes another Pc molecule with the same chirality to form a stable dimer configuration. Homochiral dimers were found on the Cu surface, demonstrating the chiral specificity of Pc dimerization. The mechanism for this chiral recognition process is identified, disclosing the critical role of the particular adsorption geometry of the chiral dimers on the Cu surface.展开更多
The experimental results of the adsorption of CO on clean and potassium-modified vicinal Cu (100) surfaces at 125 K were present. We studied three surfaces under identical experimental conditions. At 125 K, potassium ...The experimental results of the adsorption of CO on clean and potassium-modified vicinal Cu (100) surfaces at 125 K were present. We studied three surfaces under identical experimental conditions. At 125 K, potassium forms disordered structure on vicinals and CO adsorbs only on sites not occupied by K. It was found that a small percent of the CO molecules dissociate on the stepped interfaces. The influence of steps dominates over pre-adsorbed alkali atoms at 125 K.展开更多
基金supported by the National Basic Research Program of China(2012CB933001)the National Natural Science Foundation of China(21173058,21203038)
文摘We investigated the orientations of interface dipole moments of individual non-planar titanyl phthalocyanine(TiOPc)molecules on Cu(111)and Cu(100)substrates using scanning tunneling microscope(STM)and noncontact atomic force microscope(NC-AFM).The dipole moment orientations corresponding to two different configurations of individual TiOPc molecules were determined unambiguously.The correlation between the actual molecular structures and the corresponding STM topographies is proposed based on the sub-molecular resolution imaging and local contact potential difference(LCPD)measurements.Comparing with the pristine substrate,the LCPD shift due to the adsorption of non-planar molecule is dependent on the permanent molecular dipole,the charge transfer between the surface and the molecule,and the molecular configurations.This work would shed light on tailoring interfacial electronic properties and controlling local physical properties via polar molecule adsorption.
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.
基金the National Natural Science Foundation of China(20673019,20773024)the Science Foundation of Fujian Province (2006J0256, Z0513005)the Funding of Fuzhou University(XRC-0732, 2008-XQ-07)
文摘The HCNH and CNH2 adsorption on different coordination sites of Cu（100） was theoretically studied considering the cluster approach. The present calculations show that the bridge site is the most favorite for CNH2 perpendicularly adsorbed on the Cu（100） surface via the C atom. For HCNH absorbed on the Cu（100） surface, the parallel adsorption mode with the C and N atoms nearly directly above the adjacent top sites of Cu（100） surface is the most favored. Both CNH2 and HCNH are strongly bound to the Cu（100） surface with CNH2 which is lightly stable （2.51 kJ·mol^-1）, indicating that both species may be co-adsorbed on the Cu（100） surface.
基金This research was supported by the National Natural Science Foundation of China (20273013, 20303002), the Educational Foundation of Fujian Province (2002F010), and the Foundation of State Key Laboratory of Structural Chemistry (020051) and Fuzhou University (2004XY04)
文摘The adsorption and reaction of O ＋ CN → OCN on Cu（100） are studied by using density functional theory and cluster model. Cu14 cluster model is used to simulate the surface. The calculated results show that the OCN species with the molecule perpendicular to the surface via N atom （N-down） is more favorable than other adsorption models, and the N-down at the bridge site is the most favorable. For N-down, calculated OCN symmetric and asymmetric stretching frequencies are all blue-shifted compared with the calculated values of free and in good agreement with the experiments. The charge transfer from the surface to the OCN species leads to that the bonding of OCN to the metal surface is largely ionic. The present studies also show that CN with the molecule perpendicular to the surface via C atom （NC-down） at the top site is the most stable. Except NC-down at the top site, the calculated CN stretching frequencies are all red-shifted. With O coadsorbed at the hollow site, the adsorption of NC-down at the next nearest bridge or top site is energetically more favorable than that at the adjacent hollow site. The reaction of O ＋ CN → OCN on Cu（100） has no energy barrier via both Eley-Rideal and Langmuir-Hinshelwood processes.
基金Acknowledgements This work was supported by the National Basic Research Program of China （No. 2013CB934200） and the National Natural Science Foundation of China （Nos. 10979015 and 50976048）. L. W. acknowledges the financial support from the Program for New Century Excellent Talents in University, Ministry of Education of the People＇s Republic of China （No. NECT-11-1003） and Jiangxi Provincial ＂Ganpo Talents 555 Projects＂. M. D. D. acknowledges financial support from the Danish National Research Foundation, the Carlsberg Foundation, and the Villum Foundation.
文摘The molecular-level identification of a chiral recognition process of phthalocyanine （Pc） was studied on a Cu（100） surface by scanning tunneling microscopy （STM）. STM revealed that a chiral Pc molecule forms a series of metastable dimer configurations with other Pc molecules. Eventually, the Pc molecule recognizes another Pc molecule with the same chirality to form a stable dimer configuration. Homochiral dimers were found on the Cu surface, demonstrating the chiral specificity of Pc dimerization. The mechanism for this chiral recognition process is identified, disclosing the critical role of the particular adsorption geometry of the chiral dimers on the Cu surface.
文摘The experimental results of the adsorption of CO on clean and potassium-modified vicinal Cu (100) surfaces at 125 K were present. We studied three surfaces under identical experimental conditions. At 125 K, potassium forms disordered structure on vicinals and CO adsorbs only on sites not occupied by K. It was found that a small percent of the CO molecules dissociate on the stepped interfaces. The influence of steps dominates over pre-adsorbed alkali atoms at 125 K.
