Pure and Smdoped NdOnanophosphors were synthesized using modified Pechini method. The phase formation with symmetry of the sample is confirmed by the Rietveld refinement of the powder Xray diffraction(PXRD) data. The ...Pure and Smdoped NdOnanophosphors were synthesized using modified Pechini method. The phase formation with symmetry of the sample is confirmed by the Rietveld refinement of the powder Xray diffraction(PXRD) data. The surface morphology and the crystallite size were examined using scanning electron microscopy(SEM) and transmission electron microscopy(TEM) and the results confirmed that the synthesized particles are in nanosize. The energy-dispersive X-ray(EDX) analysis was done to confirm the purity of the sample. The optical properties of the sample were studied using ultraviolet-visible range(UV-Vis) spectroscopic analysis and photoluminescence studies. The calculated band gap of the synthesized NdOwas found to be higher than that of bulk NdO. The photoluminescence(PL) of the prepared samples reveals that doping with Sm3+ ion has influenced the optical properties. Quantitative investigation on charge density distribution was done by analysing the 3-dimensional and 2-dimensional charge density maps drawn along the bonding directions. The maximum entropy method(MEM)/Rietveld analysis was used for the first time to analyse the charge density in the chosen system. Charge density arrangement in the unit cell is correlated to the analysed photoluminescent(PL) properties. The spectral behaviour of the samples has been explained through charge ordering which are verified using experimental data obtained. The studies on these materials have shown that these nanophosphors will provide promising application for near-ultraviolet lightemitting diodes(n-UV-LEDs).展开更多
Smearing methods have been used to compute temperature-dependent phonon dispersions and predict critical temperatures of charge density waves,but usually lead to a much higher result because of its ambiguousmechanism ...Smearing methods have been used to compute temperature-dependent phonon dispersions and predict critical temperatures of charge density waves,but usually lead to a much higher result because of its ambiguousmechanism for modeling temperature effects.Here,a three-temperaturemodel was developed to describe the energy transfer process between electrons,soft-mode and non-soft-mode phonons.In particular,mode-selective smearing induced soft-mode phonons were assigned a temperature to analyze its contributions to the relaxation between electrons and phonons.A relative standard was established to screen soft-mode phonons quantitatively for different materials.In addition,three smearing methods(Fermi–Dirac,Gaussian,and Methfessel–Paxton)and eight materials(monolayer or bulk TX_(2),T=Ti,Nb,Ta and X=Se,S)were tested.Critical temperatures corrected by the three-temperature model were in great agreement with experimental results.This work provides new insights into correctly predicting critical temperatures of charge density waves,addressing the relaxation process of electrons and phonons using smearing method and determining phase transitions by phonon softening.展开更多
In this paper,we analyze the dependence of the topological charge density from the overlap operator on the Wilson mass parameter in the overlap kernel by the symmetric multi-probing source(SMP)method.We observe that n...In this paper,we analyze the dependence of the topological charge density from the overlap operator on the Wilson mass parameter in the overlap kernel by the symmetric multi-probing source(SMP)method.We observe that non-trivial topological objects are removed as the Wilson mass is increased.A comparison of topological charge density calculated by the SMP method using the fermionic definition with that of the gluonic definition by the Wilson flow method is shown.A matching procedure for these two methods is used.We find that there is a best match for topological charge density between the gluonic definition with varied Wilson flow time and the fermionic definition with varied Wilson mass.By using the matching procedure,the proper flow time of Wilson flow in the calculation of topological charge density can be estimated.As the lattice spacing a decreases,the proper flow time also decreases,as expected.展开更多
Amount and properties of roots surface charge are important for nutrient uptake and balance in plants. Roots surface charge markedly varies at different rizosphere conditions (particularly pH and ionic strength), whic...Amount and properties of roots surface charge are important for nutrient uptake and balance in plants. Roots surface charge markedly varies at different rizosphere conditions (particularly pH and ionic strength), which can markedly alter during vegetation season. Among recently available measuring methods, surface charge-pH dependence of roots (as well as other biological objects) is most easily evaluated by potentiometric titration. Use of this method is also easy at different ionic strengths. Potentiometric titration also allows for estimation of the distribution of charge generating surface groups. However, many applications of this method seem to be based either on incorrect methodical or theoretical approaches. In this paper we discuss the methodical and theoretical backgrounds of the titration method. Basing on experimental titration curves of roots of barley grown in nutrient solution, we show inconsistency of surface charge results obtained at different measuring conditions. Limitations of theoretical interpretations of the results are outlined also.展开更多
The electronic and physical properties of PtmPdn （m＋n≤5） metal clusters and their interactions with dioxygen have been studied by using hybrid density functional B3LYP method. The total energies, atomization energ...The electronic and physical properties of PtmPdn （m＋n≤5） metal clusters and their interactions with dioxygen have been studied by using hybrid density functional B3LYP method. The total energies, atomization energies, vibration frequencies, and charge distributions were reported. The Pt-Pt bridge site modified by Pd atoms was found to be the most active site for the dissociation of dioxygen, which was mainly due to the change of electronic structures of the Pt atoms in bimetallic Pt-Pd clusters.展开更多
在对高压直流(HVDC)输电线路下的电磁环境进行预测时,地面合成场强和离子流密度的计算问题实际上是一个多维非线性问题。在对剖分单元进行处理时,为了解决传统的有限元方法、上流有限元法采取线性假设与线性插值,存在计算量大、精度差...在对高压直流(HVDC)输电线路下的电磁环境进行预测时,地面合成场强和离子流密度的计算问题实际上是一个多维非线性问题。在对剖分单元进行处理时,为了解决传统的有限元方法、上流有限元法采取线性假设与线性插值,存在计算量大、精度差、算法效率低的问题,提出一种新的非线性空间电荷密度插值方法,从理论上推导了算法的实现过程,并基于上流有限元方法对离子电流密度方程进行迭代求解。采用该算法对现场运行的±500 k V和±800 k V输电线路离子流场进行了理论计算与现场实地测量,并将理论计算结果与实际测量结果进行了对比,结果表明:所提出的算法能在减少计算量的同时提高计算的准确度。针对风速对双极离子流场影响的研究较少的情况,研究讨论了不同风速影响下的双极离子流场问题,得到了风速对双极离子流场地面最大合成场强和离子流密度影响的规律,为新的直流输电线路的设计提供了有力的参考。展开更多
Based on density functional theory and electronegativity equalization principle, a σπ model, which considers the structure of double bond for the first time, is developed. In this model the double bond is partitione...Based on density functional theory and electronegativity equalization principle, a σπ model, which considers the structure of double bond for the first time, is developed. In this model the double bond is partitioned into one σ bond region and four π bond regions. The atom bond electronegativity equalization method plus σπ model(ABEEM σπ ) is then proposed for the calculation of charge distribution and charge polarization in large molecules. It has been shown that the results of charge distribution in large molecules obtained by ABEEM σπ model agree with those obtained by ab initio method very well. In addition, the model can be used to explain the region selectivity of Diels Alder reaction successfully. All these indicate that ABEEM σπ model is reasonable and reliable.展开更多
为研究高压直流(HVDC)输电系统中油纸绝缘的老化状态与空间电荷效应对其击穿特性的影响,采用加速热老化处理得到3种不同老化程度的油纸绝缘试样,通过同极性不同幅值的预压方式注入空间电荷,测量其击穿电压;采用电声脉冲法(PEA)在室温下...为研究高压直流(HVDC)输电系统中油纸绝缘的老化状态与空间电荷效应对其击穿特性的影响,采用加速热老化处理得到3种不同老化程度的油纸绝缘试样,通过同极性不同幅值的预压方式注入空间电荷,测量其击穿电压;采用电声脉冲法(PEA)在室温下观察试品的空间电荷分布,进一步分析了油纸内部的电场分布情况和陷阱分布特性。实验结果表明:经3 k V同极性预压后试品的击穿电压整体高于未经预压处理的试品;且随着油纸绝缘老化程度的加剧,介质内部浅陷阱密度增大;随着电荷注入量的逐渐增加、电荷效应的增强,击穿电压有所提高。但经4 k V同极性预压后试品的击穿电压整体低于经3 k V同极性预压后试品的击穿电压;因此,在实际运行中,同极性预压幅值超过一定阈值时反而会出现击穿电压降低的现象,应引起特别注意。展开更多
文摘Pure and Smdoped NdOnanophosphors were synthesized using modified Pechini method. The phase formation with symmetry of the sample is confirmed by the Rietveld refinement of the powder Xray diffraction(PXRD) data. The surface morphology and the crystallite size were examined using scanning electron microscopy(SEM) and transmission electron microscopy(TEM) and the results confirmed that the synthesized particles are in nanosize. The energy-dispersive X-ray(EDX) analysis was done to confirm the purity of the sample. The optical properties of the sample were studied using ultraviolet-visible range(UV-Vis) spectroscopic analysis and photoluminescence studies. The calculated band gap of the synthesized NdOwas found to be higher than that of bulk NdO. The photoluminescence(PL) of the prepared samples reveals that doping with Sm3+ ion has influenced the optical properties. Quantitative investigation on charge density distribution was done by analysing the 3-dimensional and 2-dimensional charge density maps drawn along the bonding directions. The maximum entropy method(MEM)/Rietveld analysis was used for the first time to analyse the charge density in the chosen system. Charge density arrangement in the unit cell is correlated to the analysed photoluminescent(PL) properties. The spectral behaviour of the samples has been explained through charge ordering which are verified using experimental data obtained. The studies on these materials have shown that these nanophosphors will provide promising application for near-ultraviolet lightemitting diodes(n-UV-LEDs).
基金supported by the Guangdong Special Support Program(Grant No.2021TQ06C953)the Shenzhen Science and Technology Programs(Grant No.JCYJ20241202123506009 and GXWD20220811164433002).
文摘Smearing methods have been used to compute temperature-dependent phonon dispersions and predict critical temperatures of charge density waves,but usually lead to a much higher result because of its ambiguousmechanism for modeling temperature effects.Here,a three-temperaturemodel was developed to describe the energy transfer process between electrons,soft-mode and non-soft-mode phonons.In particular,mode-selective smearing induced soft-mode phonons were assigned a temperature to analyze its contributions to the relaxation between electrons and phonons.A relative standard was established to screen soft-mode phonons quantitatively for different materials.In addition,three smearing methods(Fermi–Dirac,Gaussian,and Methfessel–Paxton)and eight materials(monolayer or bulk TX_(2),T=Ti,Nb,Ta and X=Se,S)were tested.Critical temperatures corrected by the three-temperature model were in great agreement with experimental results.This work provides new insights into correctly predicting critical temperatures of charge density waves,addressing the relaxation process of electrons and phonons using smearing method and determining phase transitions by phonon softening.
基金Supported by the National Natural Science Foundation of China(NSFC)(11335001)。
文摘In this paper,we analyze the dependence of the topological charge density from the overlap operator on the Wilson mass parameter in the overlap kernel by the symmetric multi-probing source(SMP)method.We observe that non-trivial topological objects are removed as the Wilson mass is increased.A comparison of topological charge density calculated by the SMP method using the fermionic definition with that of the gluonic definition by the Wilson flow method is shown.A matching procedure for these two methods is used.We find that there is a best match for topological charge density between the gluonic definition with varied Wilson flow time and the fermionic definition with varied Wilson mass.By using the matching procedure,the proper flow time of Wilson flow in the calculation of topological charge density can be estimated.As the lattice spacing a decreases,the proper flow time also decreases,as expected.
文摘Amount and properties of roots surface charge are important for nutrient uptake and balance in plants. Roots surface charge markedly varies at different rizosphere conditions (particularly pH and ionic strength), which can markedly alter during vegetation season. Among recently available measuring methods, surface charge-pH dependence of roots (as well as other biological objects) is most easily evaluated by potentiometric titration. Use of this method is also easy at different ionic strengths. Potentiometric titration also allows for estimation of the distribution of charge generating surface groups. However, many applications of this method seem to be based either on incorrect methodical or theoretical approaches. In this paper we discuss the methodical and theoretical backgrounds of the titration method. Basing on experimental titration curves of roots of barley grown in nutrient solution, we show inconsistency of surface charge results obtained at different measuring conditions. Limitations of theoretical interpretations of the results are outlined also.
基金This work was partly supported by Innovation Foundation of the Chinese Academy of Sciences (K2003D2), National Natural Science Foundation of China (No. 20173060), Hi-tech Research and Development Program of China (2003AA517040) and Knowledge Innovation Program of the Chinese Academy of Sciences (KGCX2-SW-310)
文摘The electronic and physical properties of PtmPdn （m＋n≤5） metal clusters and their interactions with dioxygen have been studied by using hybrid density functional B3LYP method. The total energies, atomization energies, vibration frequencies, and charge distributions were reported. The Pt-Pt bridge site modified by Pd atoms was found to be the most active site for the dissociation of dioxygen, which was mainly due to the change of electronic structures of the Pt atoms in bimetallic Pt-Pd clusters.
文摘在对高压直流(HVDC)输电线路下的电磁环境进行预测时,地面合成场强和离子流密度的计算问题实际上是一个多维非线性问题。在对剖分单元进行处理时,为了解决传统的有限元方法、上流有限元法采取线性假设与线性插值,存在计算量大、精度差、算法效率低的问题,提出一种新的非线性空间电荷密度插值方法,从理论上推导了算法的实现过程,并基于上流有限元方法对离子电流密度方程进行迭代求解。采用该算法对现场运行的±500 k V和±800 k V输电线路离子流场进行了理论计算与现场实地测量,并将理论计算结果与实际测量结果进行了对比,结果表明:所提出的算法能在减少计算量的同时提高计算的准确度。针对风速对双极离子流场影响的研究较少的情况,研究讨论了不同风速影响下的双极离子流场问题,得到了风速对双极离子流场地面最大合成场强和离子流密度影响的规律,为新的直流输电线路的设计提供了有力的参考。
文摘Based on density functional theory and electronegativity equalization principle, a σπ model, which considers the structure of double bond for the first time, is developed. In this model the double bond is partitioned into one σ bond region and four π bond regions. The atom bond electronegativity equalization method plus σπ model(ABEEM σπ ) is then proposed for the calculation of charge distribution and charge polarization in large molecules. It has been shown that the results of charge distribution in large molecules obtained by ABEEM σπ model agree with those obtained by ab initio method very well. In addition, the model can be used to explain the region selectivity of Diels Alder reaction successfully. All these indicate that ABEEM σπ model is reasonable and reliable.
文摘为研究高压直流(HVDC)输电系统中油纸绝缘的老化状态与空间电荷效应对其击穿特性的影响,采用加速热老化处理得到3种不同老化程度的油纸绝缘试样,通过同极性不同幅值的预压方式注入空间电荷,测量其击穿电压;采用电声脉冲法(PEA)在室温下观察试品的空间电荷分布,进一步分析了油纸内部的电场分布情况和陷阱分布特性。实验结果表明:经3 k V同极性预压后试品的击穿电压整体高于未经预压处理的试品;且随着油纸绝缘老化程度的加剧,介质内部浅陷阱密度增大;随着电荷注入量的逐渐增加、电荷效应的增强,击穿电压有所提高。但经4 k V同极性预压后试品的击穿电压整体低于经3 k V同极性预压后试品的击穿电压;因此,在实际运行中,同极性预压幅值超过一定阈值时反而会出现击穿电压降低的现象,应引起特别注意。
