The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerim...The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerimental results show that the symmetric TiO2 membranes display better sintering activity in the air than in argon, and the mean pore diameters and porosities of the membrane sintered in argon are higher than those of the membrane sintered in the air at the same temperature. The surface compositions of the symmetric TiO2 membrane sintered in the air and in argon at different temperatures, as studied by X-ray photoelectron spectroscopy, are discussed in terms of their chemical composition, with particular emphasis on the valence state of the titanium ions. The correlation between the valence state of the titanium ions at the surface and the surface charge properties is examined.It is found that the presence of Ti^3+, introduced at the surface of the symmetric TiO2 membranes by sintering in a lower partial pressure of oxygen, is related to a significant decrease in the isoelectric point. TiO2 with Ti^4+ at the interface has an isoelectric point of 5.1, but the non-stoichiometric TiO2-x with Ti^3+ at the interface has a lower isoelectric point of 3.6.展开更多
Molecular dipole moments computed at the levels of HF/STO-3G, HF/6-31G(d, p), HF/6-311+G(2d, 2p), MP2/6-31G(d, p) and MP2/6-311+G(2d, 2p) have been investigated. HF/6-311+G(2d, 2p) was found to be the relatively good ...Molecular dipole moments computed at the levels of HF/STO-3G, HF/6-31G(d, p), HF/6-311+G(2d, 2p), MP2/6-31G(d, p) and MP2/6-311+G(2d, 2p) have been investigated. HF/6-311+G(2d, 2p) was found to be the relatively good choice to compute MKS charges for reproducing the experimental values of molecular dipole moments. Root mean square deviation of computed dipole moments for 21 small polar molecules is about 0.1969 D.展开更多
First-principles calculations have been performed for the study of the electronic band structure and ferromagnetic properties of double perovskite Ca2CrSbO6. The density of states, total energy, spin magnetic moment, ...First-principles calculations have been performed for the study of the electronic band structure and ferromagnetic properties of double perovskite Ca2CrSbO6. The density of states, total energy, spin magnetic moment, and charge density were calculated and analyzed in details. It is found that Ca2CrSbO6 has a stable ferromagnetic ground state and the spin magnetic moment per molecule is about 2.99#B. The chromium contributes the most in the total magnetic moments. The results indicate that Ca2CrSbO6 is half-metallic.展开更多
Using Geant4 Monte Carlo code and Technology Computer-Aided Design(TCAD) simulation,energy deposition and charge collection of single event effects(SEE) are studied,which are induced by low-energy protons and α parti...Using Geant4 Monte Carlo code and Technology Computer-Aided Design(TCAD) simulation,energy deposition and charge collection of single event effects(SEE) are studied,which are induced by low-energy protons and α particles in small feature size devices.We analyzed charge collection of SEE especially at Bragg's peak and obtained two types of deposited energy distributions of protons and α particles at different incident energies.The two components of the total charge collected are quantified,which are due to drift current of the space charge region and current in the funnel region separately.Results explain the high soft error rate in experiments of low energy proton.展开更多
This paper proposes a new mechanism to explain the performance of thin dye-sensitized solar cells (DSSC). Near-stoichiometric flower-like Cu2ZnSnS4 (CZTS) microspheres with a high specific surface area was fabri- ...This paper proposes a new mechanism to explain the performance of thin dye-sensitized solar cells (DSSC). Near-stoichiometric flower-like Cu2ZnSnS4 (CZTS) microspheres with a high specific surface area was fabri- cated for use as the photocathode in a DSSC. To improve the extraction and transfer of electrons, graphene was added to the CZTS. A DSSC with a 10-gin TiO2 pho- toanode layer exhibited a slightly degraded efficiency with a CZTS-graphene photocathode, relative to a Pt counter electrode (CE). Nevertheless, when the thickness of the TiO2 photoanode was reduced to 2 lam, the efficiency of a DSSC with a CZTS-graphene photocathode was greater than that of a Pt-DSSC. It is speculated that, unlike the Pt CE, a CZTS-graphene photocathode not only collects electrons from an external circuit and catalyzes the reduction of the triiodide ions in the electrolyte, but also utilizes unabsorbed photons to produce photo-excited electrons and suppresses charge recombination, thus enhancing the performance of the cell. The use of narrowband gap p-type semiconductors as photocathodes offers a new means of fabricating thin dye-sensitized solar cells and effectively improving the cell performance.展开更多
Non-hermiticity presents a vast newly opened territory that harbors new physics and applications such as lasing and sensing.However,only non-Hermitian systems with real eigenenergies are stable,and great efforts have ...Non-hermiticity presents a vast newly opened territory that harbors new physics and applications such as lasing and sensing.However,only non-Hermitian systems with real eigenenergies are stable,and great efforts have been devoted in designing them through enforcing parity-time(PT)symmetry.In this work,we exploit a lesser-known dynamical mechanism for enforcing real-spectra,and develop a comprehensive and versatile approach for designing new classes of parent Hamiltonians with real spectra.Our design approach is based on a new electrostatics analogy for modifed non-Hermitian bulk-boundary correspondence,where electrostatic charge corresponds to density of states and electric felds correspond to complex spectral fow.As such,Hamiltonians of any desired spectra and state localization profle can be reverse-engineered,particularly those without any guiding symmetry principles.By recasting the diagonalization of non-Hermitian Hamiltonians as a Poisson boundary value problem,our electrostatics analogy also transcends the gain/loss-induced compounding of foating-point errors in traditional numerical methods,thereby allowing access to far larger system sizes.展开更多
基金Supported by the National-Basic Research Program of China (2003CB615707) and the National Natural Science Foundation of China (20636020).
文摘The effects of sintering atmosphere on the properties of symmetric TiO2 membranes are studied with regard to sintering behavior, porosity, mean pore size, surface comPosition. and surface charge properties. The exerimental results show that the symmetric TiO2 membranes display better sintering activity in the air than in argon, and the mean pore diameters and porosities of the membrane sintered in argon are higher than those of the membrane sintered in the air at the same temperature. The surface compositions of the symmetric TiO2 membrane sintered in the air and in argon at different temperatures, as studied by X-ray photoelectron spectroscopy, are discussed in terms of their chemical composition, with particular emphasis on the valence state of the titanium ions. The correlation between the valence state of the titanium ions at the surface and the surface charge properties is examined.It is found that the presence of Ti^3+, introduced at the surface of the symmetric TiO2 membranes by sintering in a lower partial pressure of oxygen, is related to a significant decrease in the isoelectric point. TiO2 with Ti^4+ at the interface has an isoelectric point of 5.1, but the non-stoichiometric TiO2-x with Ti^3+ at the interface has a lower isoelectric point of 3.6.
基金The project was supported by the National Science Foundation (29773021) Provincial Educational Foundation of Jiangsu (98KJB150001).
文摘Molecular dipole moments computed at the levels of HF/STO-3G, HF/6-31G(d, p), HF/6-311+G(2d, 2p), MP2/6-31G(d, p) and MP2/6-311+G(2d, 2p) have been investigated. HF/6-311+G(2d, 2p) was found to be the relatively good choice to compute MKS charges for reproducing the experimental values of molecular dipole moments. Root mean square deviation of computed dipole moments for 21 small polar molecules is about 0.1969 D.
基金Supported by the Natural Science Foundation of China under Grant Nos. 10774053 and 2006CB921605
文摘First-principles calculations have been performed for the study of the electronic band structure and ferromagnetic properties of double perovskite Ca2CrSbO6. The density of states, total energy, spin magnetic moment, and charge density were calculated and analyzed in details. It is found that Ca2CrSbO6 has a stable ferromagnetic ground state and the spin magnetic moment per molecule is about 2.99#B. The chromium contributes the most in the total magnetic moments. The results indicate that Ca2CrSbO6 is half-metallic.
基金supported by the State Key Program of National Natural Science Foundation of China (Grant No 60836004)the National Natural Science Foundation of China (Grant Nos 61076025 and 61006070)the Specialized Research Fund for the Doctoral Program of Higher Education of China (Grant No 20104307120006)
文摘Using Geant4 Monte Carlo code and Technology Computer-Aided Design(TCAD) simulation,energy deposition and charge collection of single event effects(SEE) are studied,which are induced by low-energy protons and α particles in small feature size devices.We analyzed charge collection of SEE especially at Bragg's peak and obtained two types of deposited energy distributions of protons and α particles at different incident energies.The two components of the total charge collected are quantified,which are due to drift current of the space charge region and current in the funnel region separately.Results explain the high soft error rate in experiments of low energy proton.
基金This work was supported by the National Natural Science Foundation of China (51272033, 51572037 and 51335002), the Priority Academic Program Development of Jiangsu Higher Education Institutions and the Natural Science Foundation of the Jiangsu Higher Education Institutions of China (14KJA430001).
文摘This paper proposes a new mechanism to explain the performance of thin dye-sensitized solar cells (DSSC). Near-stoichiometric flower-like Cu2ZnSnS4 (CZTS) microspheres with a high specific surface area was fabri- cated for use as the photocathode in a DSSC. To improve the extraction and transfer of electrons, graphene was added to the CZTS. A DSSC with a 10-gin TiO2 pho- toanode layer exhibited a slightly degraded efficiency with a CZTS-graphene photocathode, relative to a Pt counter electrode (CE). Nevertheless, when the thickness of the TiO2 photoanode was reduced to 2 lam, the efficiency of a DSSC with a CZTS-graphene photocathode was greater than that of a Pt-DSSC. It is speculated that, unlike the Pt CE, a CZTS-graphene photocathode not only collects electrons from an external circuit and catalyzes the reduction of the triiodide ions in the electrolyte, but also utilizes unabsorbed photons to produce photo-excited electrons and suppresses charge recombination, thus enhancing the performance of the cell. The use of narrowband gap p-type semiconductors as photocathodes offers a new means of fabricating thin dye-sensitized solar cells and effectively improving the cell performance.
基金supported by Singapore’s MOE Tier I grant WBS No.A-800022-00-00。
文摘Non-hermiticity presents a vast newly opened territory that harbors new physics and applications such as lasing and sensing.However,only non-Hermitian systems with real eigenenergies are stable,and great efforts have been devoted in designing them through enforcing parity-time(PT)symmetry.In this work,we exploit a lesser-known dynamical mechanism for enforcing real-spectra,and develop a comprehensive and versatile approach for designing new classes of parent Hamiltonians with real spectra.Our design approach is based on a new electrostatics analogy for modifed non-Hermitian bulk-boundary correspondence,where electrostatic charge corresponds to density of states and electric felds correspond to complex spectral fow.As such,Hamiltonians of any desired spectra and state localization profle can be reverse-engineered,particularly those without any guiding symmetry principles.By recasting the diagonalization of non-Hermitian Hamiltonians as a Poisson boundary value problem,our electrostatics analogy also transcends the gain/loss-induced compounding of foating-point errors in traditional numerical methods,thereby allowing access to far larger system sizes.