The thermodynamic properties of the bilayer ruthenate compound Sr3Ru2O7 at very low temperatures are inves- tigated by using a tight-binding model yielding the realistic band structure combined with the on-site intera...The thermodynamic properties of the bilayer ruthenate compound Sr3Ru2O7 at very low temperatures are inves- tigated by using a tight-binding model yielding the realistic band structure combined with the on-site interactions treated at the mean-field level. We find that both the total density of states at the Fermi energy and the entropy exhibit a sudden increase near the critical magnetic field for the nematic phase, echoing the experimental find- ings. A new mechanism to explain the anisotropic transport properties is proposed based on scatterings at the anisotropic domain boundaries. Our results suggest that extra cares are necessary to isolate the contributions due to the quantum criticality from the band structure singularity in Sr3Ru2O7.展开更多
The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G* level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular...The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G* level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound's structure-activity relationship.展开更多
Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were ...Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×10^5 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume(CVθ),entropy(Sθ),standard heat of formation(△fHθ) and standard free energy of formation(△fGθ) of PBPTs and the structural parameters(the most negative atomic charge(q^-) and molecular average polarizability(α)).These models presented better correlations(r^2〉0.97).And they were validated by variance inflation factor(VIF) and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.展开更多
DFT-B3LYP/6-311G** method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene(PCFRT) congeners and calculate their thermo-dynamic properties in the ideal gas state,such as ...DFT-B3LYP/6-311G** method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene(PCFRT) congeners and calculate their thermo-dynamic properties in the ideal gas state,such as heat capacity at constant volume(Cv),entropy(S),standard enthalpy of formation(ΔfH) and standard Gibbs free energy of formation(ΔfG).The relations of Cv,S,ΔfH and ΔfG with the number and position of chlorine atoms have also been explored,from which the relative stability of PCFRT congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation(Δr,fG).It was found that some of the PCFRT isomers are in a nonplanar configuration and there are intramolecular Cl…Cl weak interactions in some of the isomers.With increasing the number of chlorine atoms,the values of ΔfH and ΔfG of the most stable PCFRT isomers decrease initially and then increase.The values of ΔfH and ΔfG of PCFRT congeners with the same number of chlorine atoms show a strong dependence on the positions of chlorine atoms.The relative thermodynamic stability of PCFRT isomers is determined mainly by intramolecular adjacent Cl…Cl nuclear repulsive interaction between Cl atoms at two different six-membered rings.Most PCFRT congeners are easier to form thermodynamically than their parent compound.展开更多
High levels of fine particulate matter(PM_(2.5))is linked to poor air quality and premature deaths,so haze pollution deserves the attention of the world.As abundant inorganic components in PM_(2.5),ammonium nitrate(NH...High levels of fine particulate matter(PM_(2.5))is linked to poor air quality and premature deaths,so haze pollution deserves the attention of the world.As abundant inorganic components in PM_(2.5),ammonium nitrate(NH_(4)NO_(3))formation includes two processes,the diffusion process(molecule of ammonia and nitric acid move from gas phase to liquid phase)and the ionization process(subsequent dissociation to form ions).In this study,we discuss the impact of meteorological factors,emission sources,and gaseous precursors on NH4NO3 formation based on thermodynamic theory,and identify the dominant factors during clean periods and haze periods.Results show that aerosol liquid water content has a more significant effect on ammonium nitrate formation regardless of the severity of pollution.The dust source is dominant emission source in clean periods;while a combination of coal combustion and vehicle exhaust sources is more important in haze periods.And the control of ammonia emission is more effective in reducing the formation of ammonium nitrate.The findings of this work inform the design of effective strategies to control particulate matter pollution.展开更多
The stability of cement sheath under high temperature and high pressure is one of the most critical issues for the durability of geother-mal well systems.In this study,a two-dimensional plane-strain finite element cod...The stability of cement sheath under high temperature and high pressure is one of the most critical issues for the durability of geother-mal well systems.In this study,a two-dimensional plane-strain finite element code was developed to investigate the coupled thermo-mechanical behaviors of the casing-cement-formation system.Different from previous linear elastic analyses,a thermoelasto-plastic con-stitutive model based on the thermodynamic theory was adopted for the cement sheath.It is shown that the finite element simulations using the proposed model provide a more accurate and realistic prediction of stress–strain responses of the cement sheath under high temperature.The results demonstrate that the radial stress concentration and the tensile strain concentration occur at both the cement–casing interface and the cement–formation interface,where the cement sheath is most likely to fail.High strength and low stiff-ness in the cement sheath and the formation are preferred for the integrity of the system.Both large thermal cycles and large differences between the internal fluid pressure and the external pressure should be avoided during operation.The new code is an alternative tool for guiding the geothermal well design.The finite element framework described herein is universal for other thermo-mechanical applications,such as energy foundations and energy tunnels.展开更多
基金Supported by the NSF DMR-1410375 and AFOSR FA9550-14-1-0168the President's Research Catalyst Award(No CA-15-327861) from the University of California Office of the Presidentthe CAS/SAFEA International Partnership Program for Creative Research Teams
文摘The thermodynamic properties of the bilayer ruthenate compound Sr3Ru2O7 at very low temperatures are inves- tigated by using a tight-binding model yielding the realistic band structure combined with the on-site interactions treated at the mean-field level. We find that both the total density of states at the Fermi energy and the entropy exhibit a sudden increase near the critical magnetic field for the nematic phase, echoing the experimental find- ings. A new mechanism to explain the anisotropic transport properties is proposed based on scatterings at the anisotropic domain boundaries. Our results suggest that extra cares are necessary to isolate the contributions due to the quantum criticality from the band structure singularity in Sr3Ru2O7.
基金Sponsored by the Youth Foundation for Natural Science from the Sichuan Provincial Education Department (No. 07ZB080)
文摘The structure optimization and frequency calculation have been carried out at the B3LYP/6-31G* level towards herbicidal monosulfuron using density functional theory.The computed results showed that the intramolecular hydrogen bond N-H…N can stabilize the molecule.IR spectra,Raman spectra and thermodynamic properties under different temperatures were also obtained.The first vertical excited state electronic transition energy was calculated by time-dependent density function theory,and absorption wavelength of the lowest energy excitation was obtained at 339.59 nm,belonging to the near UV.These results provided the basis for studies on compound's structure-activity relationship.
基金supported by the Scientific Research Foundation of Guangxi Provincial Education Department (GJKY (2006) No 26)the Research Funds of Guangxi Key Laboratory of Environmental Engineering, Protection and Assessment (0801K007, 0801K008)
文摘Complete optimization was conducted for 136 polybromo-phenoxathiin congeners(PBPTs) on the B3LYP/6-31G* level with Gaussian 03 program.The structural parameters and thermodynamical parameters of each molecule were obtained under the standard state of 298.15 K and 1.013×10^5 Pa.Reverse linear regression was employed to establish the quantitative structure-property correlation models between heat capacity at constant volume(CVθ),entropy(Sθ),standard heat of formation(△fHθ) and standard free energy of formation(△fGθ) of PBPTs and the structural parameters(the most negative atomic charge(q^-) and molecular average polarizability(α)).These models presented better correlations(r^2〉0.97).And they were validated by variance inflation factor(VIF) and t-test,which can better explain the regularity of thermodynamical property of PBPTs,and has good stability and great prediction ability.
基金Sponsored by Natural Science Fundamental Research Program of Henan Provincial Education Department (No.2009A150022)Young Backbone Teacher Program of Xinyang Normal University
文摘DFT-B3LYP/6-311G** method has been used to optimize molecular geometric structures of 527 polychlorinated fluoranthene(PCFRT) congeners and calculate their thermo-dynamic properties in the ideal gas state,such as heat capacity at constant volume(Cv),entropy(S),standard enthalpy of formation(ΔfH) and standard Gibbs free energy of formation(ΔfG).The relations of Cv,S,ΔfH and ΔfG with the number and position of chlorine atoms have also been explored,from which the relative stability of PCFRT congeners was theoretically proposed according to the magnitude of the relative standard Gibbs free energy of formation(Δr,fG).It was found that some of the PCFRT isomers are in a nonplanar configuration and there are intramolecular Cl…Cl weak interactions in some of the isomers.With increasing the number of chlorine atoms,the values of ΔfH and ΔfG of the most stable PCFRT isomers decrease initially and then increase.The values of ΔfH and ΔfG of PCFRT congeners with the same number of chlorine atoms show a strong dependence on the positions of chlorine atoms.The relative thermodynamic stability of PCFRT isomers is determined mainly by intramolecular adjacent Cl…Cl nuclear repulsive interaction between Cl atoms at two different six-membered rings.Most PCFRT congeners are easier to form thermodynamically than their parent compound.
基金the National Natural Science Foundation of China(No.42077191)the Fundamental Research Funds for the Central Universities(Nos.63213072,63213074)+1 种基金the GDAS’Project of Science and Technology Development(No.2021GDASYL-20210103058)the Guangdong Basic and Applied Basic Research Foundation(No.2022A1515012165),The Blue Sky Foundation.
文摘High levels of fine particulate matter(PM_(2.5))is linked to poor air quality and premature deaths,so haze pollution deserves the attention of the world.As abundant inorganic components in PM_(2.5),ammonium nitrate(NH_(4)NO_(3))formation includes two processes,the diffusion process(molecule of ammonia and nitric acid move from gas phase to liquid phase)and the ionization process(subsequent dissociation to form ions).In this study,we discuss the impact of meteorological factors,emission sources,and gaseous precursors on NH4NO3 formation based on thermodynamic theory,and identify the dominant factors during clean periods and haze periods.Results show that aerosol liquid water content has a more significant effect on ammonium nitrate formation regardless of the severity of pollution.The dust source is dominant emission source in clean periods;while a combination of coal combustion and vehicle exhaust sources is more important in haze periods.And the control of ammonia emission is more effective in reducing the formation of ammonium nitrate.The findings of this work inform the design of effective strategies to control particulate matter pollution.
基金the financial support from the 7 th Framework Program for Research of European Commission(Grant No.612665)National Natural Science Foundation of China(NSFC,Grant No.51778338).
文摘The stability of cement sheath under high temperature and high pressure is one of the most critical issues for the durability of geother-mal well systems.In this study,a two-dimensional plane-strain finite element code was developed to investigate the coupled thermo-mechanical behaviors of the casing-cement-formation system.Different from previous linear elastic analyses,a thermoelasto-plastic con-stitutive model based on the thermodynamic theory was adopted for the cement sheath.It is shown that the finite element simulations using the proposed model provide a more accurate and realistic prediction of stress–strain responses of the cement sheath under high temperature.The results demonstrate that the radial stress concentration and the tensile strain concentration occur at both the cement–casing interface and the cement–formation interface,where the cement sheath is most likely to fail.High strength and low stiff-ness in the cement sheath and the formation are preferred for the integrity of the system.Both large thermal cycles and large differences between the internal fluid pressure and the external pressure should be avoided during operation.The new code is an alternative tool for guiding the geothermal well design.The finite element framework described herein is universal for other thermo-mechanical applications,such as energy foundations and energy tunnels.