Manganese-based perovskite is popular for research on ferromagnetic materials,and its spectroscopic studies are essential for understanding its electronic structure,dielectric,electrical,and magnetic properties.In thi...Manganese-based perovskite is popular for research on ferromagnetic materials,and its spectroscopic studies are essential for understanding its electronic structure,dielectric,electrical,and magnetic properties.In this paper,the M-edge spectra of La ions and the M-edge,L-edge,and K-edge spectra of Mn ions in LaMnO3 are calculated by considering both the free-ion multiplet calculation and the crystal field effects.We analyze spectral shapes,identify peak origins,and estimate the oxidation states of La and Mn ions in LaMnO3 theoretically.It is concluded that La ions in LaMnO3 predominantly exist in the trivalent state,while Mn ions exist primarily in the trivalent state with a minor presence of tetravalent ions.Furthermore,the calculated spectra are in better conformity with the experimental spectra when the proportion of Mn3+is 90%and Mn4+is 10%.This article enhances our comprehension of the oxidation states of La and Mn within the crystal and also provides a valuable guidance for spectroscopic investigations of other manganates.展开更多
Cross-sections for electronic excitation and de-excitation among the ground state and lowest-lying seven electronic excited states of carbon monoxide(CO)by low-energy electron impact are computed using the R-matrix me...Cross-sections for electronic excitation and de-excitation among the ground state and lowest-lying seven electronic excited states of carbon monoxide(CO)by low-energy electron impact are computed using the R-matrix method.The excitation cross-sections from the ground state to the electronic states a^(3)Π,a'^(3)Σ^(+)+and A^(1)Πagree with previous experimental and theoretical results.In addition,the cross-sections for the I^(1)Σ^(+)-and D^(1)Δstates of CO,which will cascade to CO a'^(3)Σ^(+)+and A^(1)Πstates,are calculated.Furthermore,in contrast to the typical increase in electronic excitation cross-sections with collision energy,the de-excitation cross-sections show a negative trend with increasing energy.展开更多
The lead-free perovskites Cs_(3)B_(2)X_(9)(B=Sb,Bi;X=Cl,Br,I)as the popular photoelectric materials have excellent optical properties with lower toxicity.In this study,we systematically investigate the stable monolaye...The lead-free perovskites Cs_(3)B_(2)X_(9)(B=Sb,Bi;X=Cl,Br,I)as the popular photoelectric materials have excellent optical properties with lower toxicity.In this study,we systematically investigate the stable monolayer Cs_(3)B_(2)X_(9)and bilayer vertical heterostructure Cs_(3)B_(2)X_(9)/Cs3B02X9(B,B0=Sb,Bi;X=Cl,Br,I)via first-principles simulations.By exploring the electrical structures and band edge positions,we find the band gap reduction and the band type transition in the heterostructure Cs_(3)B_(2)X_(9)/Cs3B02X9 due to the charge transfer between layers.Furthermore,the results of optical properties reveal light absorption from the visible light to UV region,especially monolayer Cs3Sb2I9 and heterostructure Cs3Sb2I9/Cs3Bi2I9,which have absorption peaks in the visible light region,leading to the possibility of photocatalytic water splitting.These results provide insights for more two-dimensional semiconductors applied in the optoelectronic and photocatalytic fields.展开更多
MoS_(2),a transition metal dichalcogenide(TMDC),has attracted significant amount of attention due to its direct bandgap,tunability and optical properties.Recently,a novel structure consisting of MoS_(2) and noble meta...MoS_(2),a transition metal dichalcogenide(TMDC),has attracted significant amount of attention due to its direct bandgap,tunability and optical properties.Recently,a novel structure consisting of MoS_(2) and noble metal nanoclusters has been reported.Inspired by this,first principle calculations are implemented to predict the structures of M_(6)X_(2) and M_(6)XX'(M=Au,Ag;X,X'=S,Se).The calculated bandgap,band edge position,and optical absorption of these structures prove that the silver compounds(Ag_(6)X_(2) and Ag_(6)XX')have great potential for catalytic water splitting.In addition,biaxial strain(tensile strain and compressive strain)is applied to adjust the properties of these materials.The bandgap presents a quasi-linear trend with the increase of the applied strain.Moreover,the transition between the direct and indirect bandgap is found.The outstanding electronic and optical properties of these materials provide strong evidence for their application in microelectronic devices,photoelectric devices,and photocatalytic materials.展开更多
A three-dimensional finite element dynamic simulation platform of the ground source heat pump system(GSHPS)is established.According to the outlet temperature of ground heat exchangers(GHEs)required by the code in summ...A three-dimensional finite element dynamic simulation platform of the ground source heat pump system(GSHPS)is established.According to the outlet temperature of ground heat exchangers(GHEs)required by the code in summer and winter,the calculated minimum buried depth of GHEs meeting the requirements is 60 m,when the number of borehole is 9.By using the established platform,the annual operation performance and cost of the GSHPS under different buried pipe depths are studied.The results show that the deeper the buried depth of GHEs is,the better the heat exchange effect of GHEs is.Compared with the GHEs with 60 m buried depth,when the buried depth of GHEs is 65 m,70 m,75 m and 80 m,the average coefficient of performance(COP)of the unit increases by 4.1%,6.3%,7.7%and 8.2%in cooling period and 1.0%,1.6%,1.8%and 1.9%in heating period,respectively.Considering the performance and initial investment of the GHSPS comprehensively,the optimal buried depth of GHEs is 60 m.However,considering the performance the system and the total cost of the system running for 20 years comprehensively,the optimal buried depth of GHEs is 70 m.展开更多
Using density functional theory, we investigated the hydrogen storage capacity of Li coated BC3 honeycomb sheet. Our result indicates 18 H2 molecules can be adsorbed on BC3Li6 complex with a storage gravimetric densit...Using density functional theory, we investigated the hydrogen storage capacity of Li coated BC3 honeycomb sheet. Our result indicates 18 H2 molecules can be adsorbed on BC3Li6 complex with a storage gravimetric density of 9.68 wt% and the average adsorption energy reaches 0.206 eV/H2. This is desirable for absorbing and desorbing H2 molecules at near ambient conditions.展开更多
Hydrogen can be trapped in the bulk materials in four forms： interstitial molecular H2, interstitial atom H, O-H＋（2Si=O-H）＋, Si-H-（4O SiH）- to affect the electronic and optical properties of amorphous silica. T...Hydrogen can be trapped in the bulk materials in four forms： interstitial molecular H2, interstitial atom H, O-H＋（2Si=O-H）＋, Si-H-（4O SiH）- to affect the electronic and optical properties of amorphous silica. Therefore, the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory. Initially, the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom. However, the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy. Sub- sequently, the optical properties such as absorption spectra, conductivity and loss functions were analyzed. It is in- dicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 eV while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 eV. However, the neutral hydrogen defects just improved the intensity of absorption spectrum. This may give insights into understanding the mechanism of laser-induced damage for optical materials.展开更多
基金Project supported by the National Natural Science Foundation of China(Grant No.11974253).
文摘Manganese-based perovskite is popular for research on ferromagnetic materials,and its spectroscopic studies are essential for understanding its electronic structure,dielectric,electrical,and magnetic properties.In this paper,the M-edge spectra of La ions and the M-edge,L-edge,and K-edge spectra of Mn ions in LaMnO3 are calculated by considering both the free-ion multiplet calculation and the crystal field effects.We analyze spectral shapes,identify peak origins,and estimate the oxidation states of La and Mn ions in LaMnO3 theoretically.It is concluded that La ions in LaMnO3 predominantly exist in the trivalent state,while Mn ions exist primarily in the trivalent state with a minor presence of tetravalent ions.Furthermore,the calculated spectra are in better conformity with the experimental spectra when the proportion of Mn3+is 90%and Mn4+is 10%.This article enhances our comprehension of the oxidation states of La and Mn within the crystal and also provides a valuable guidance for spectroscopic investigations of other manganates.
基金Project supported by the National Natural Science Foundation of China (Grant No.11974253)。
文摘Cross-sections for electronic excitation and de-excitation among the ground state and lowest-lying seven electronic excited states of carbon monoxide(CO)by low-energy electron impact are computed using the R-matrix method.The excitation cross-sections from the ground state to the electronic states a^(3)Π,a'^(3)Σ^(+)+and A^(1)Πagree with previous experimental and theoretical results.In addition,the cross-sections for the I^(1)Σ^(+)-and D^(1)Δstates of CO,which will cascade to CO a'^(3)Σ^(+)+and A^(1)Πstates,are calculated.Furthermore,in contrast to the typical increase in electronic excitation cross-sections with collision energy,the de-excitation cross-sections show a negative trend with increasing energy.
基金supported by the National Key R&D Program of China(Grant No.2017YFA0303600)the National Natural Science Foundation of China(Grant No.11974253)the Science Specialty Program of Sichuan University(Grand No.2020SCUNL210)。
文摘The lead-free perovskites Cs_(3)B_(2)X_(9)(B=Sb,Bi;X=Cl,Br,I)as the popular photoelectric materials have excellent optical properties with lower toxicity.In this study,we systematically investigate the stable monolayer Cs_(3)B_(2)X_(9)and bilayer vertical heterostructure Cs_(3)B_(2)X_(9)/Cs3B02X9(B,B0=Sb,Bi;X=Cl,Br,I)via first-principles simulations.By exploring the electrical structures and band edge positions,we find the band gap reduction and the band type transition in the heterostructure Cs_(3)B_(2)X_(9)/Cs3B02X9 due to the charge transfer between layers.Furthermore,the results of optical properties reveal light absorption from the visible light to UV region,especially monolayer Cs3Sb2I9 and heterostructure Cs3Sb2I9/Cs3Bi2I9,which have absorption peaks in the visible light region,leading to the possibility of photocatalytic water splitting.These results provide insights for more two-dimensional semiconductors applied in the optoelectronic and photocatalytic fields.
基金Projected supported by the National Natural Science Foundation of China(Grant No.11974253)the National Key R&D Program of China(Grant No.2017YFA0303600)Science Specialty Program of Sichuan University(Grant No.2020SCUNL210).
文摘MoS_(2),a transition metal dichalcogenide(TMDC),has attracted significant amount of attention due to its direct bandgap,tunability and optical properties.Recently,a novel structure consisting of MoS_(2) and noble metal nanoclusters has been reported.Inspired by this,first principle calculations are implemented to predict the structures of M_(6)X_(2) and M_(6)XX'(M=Au,Ag;X,X'=S,Se).The calculated bandgap,band edge position,and optical absorption of these structures prove that the silver compounds(Ag_(6)X_(2) and Ag_(6)XX')have great potential for catalytic water splitting.In addition,biaxial strain(tensile strain and compressive strain)is applied to adjust the properties of these materials.The bandgap presents a quasi-linear trend with the increase of the applied strain.Moreover,the transition between the direct and indirect bandgap is found.The outstanding electronic and optical properties of these materials provide strong evidence for their application in microelectronic devices,photoelectric devices,and photocatalytic materials.
基金The authors gratefully acknowledge the support from the Natural Science Foundation of China(grant No.51778115)the Fundamental Research Funds for the Central Universities(grant No.N182502043).
文摘A three-dimensional finite element dynamic simulation platform of the ground source heat pump system(GSHPS)is established.According to the outlet temperature of ground heat exchangers(GHEs)required by the code in summer and winter,the calculated minimum buried depth of GHEs meeting the requirements is 60 m,when the number of borehole is 9.By using the established platform,the annual operation performance and cost of the GSHPS under different buried pipe depths are studied.The results show that the deeper the buried depth of GHEs is,the better the heat exchange effect of GHEs is.Compared with the GHEs with 60 m buried depth,when the buried depth of GHEs is 65 m,70 m,75 m and 80 m,the average coefficient of performance(COP)of the unit increases by 4.1%,6.3%,7.7%and 8.2%in cooling period and 1.0%,1.6%,1.8%and 1.9%in heating period,respectively.Considering the performance and initial investment of the GHSPS comprehensively,the optimal buried depth of GHEs is 60 m.However,considering the performance the system and the total cost of the system running for 20 years comprehensively,the optimal buried depth of GHEs is 70 m.
基金Acknowledgement This work was supported by the National Natural Science Foundation of China （NSFC Grant No. 11374217）. Meanwhile, we are also grateful to the support of our calculation from Analytical ＆ Testing Center Sichuan University, PR China.
文摘Using density functional theory, we investigated the hydrogen storage capacity of Li coated BC3 honeycomb sheet. Our result indicates 18 H2 molecules can be adsorbed on BC3Li6 complex with a storage gravimetric density of 9.68 wt% and the average adsorption energy reaches 0.206 eV/H2. This is desirable for absorbing and desorbing H2 molecules at near ambient conditions.
基金Project supported by the Science and Technology of Hubei Provincial Department of Education(No.B2017098)
文摘Hydrogen can be trapped in the bulk materials in four forms： interstitial molecular H2, interstitial atom H, O-H＋（2Si=O-H）＋, Si-H-（4O SiH）- to affect the electronic and optical properties of amorphous silica. Therefore, the electronic and optical properties of defect-free and hydrogen defects in amorphous silica were performed within the scheme of density functional theory. Initially, the negative charged states hydrogen defects introduced new defect level between the valence band top and conduction band bottom. However, the neutral and positive charged state hydrogen defects made both the valence band and conduction band transfer to the lower energy. Sub- sequently, the optical properties such as absorption spectra, conductivity and loss functions were analyzed. It is in- dicated that the negative hydrogen defects caused the absorption peak ranging from 0 to 2.0 eV while the positive states produced absorption peaks at lower energy and two strong absorption peaks arose at 6.9 and 9.0 eV. However, the neutral hydrogen defects just improved the intensity of absorption spectrum. This may give insights into understanding the mechanism of laser-induced damage for optical materials.
