In this perspective,we review the chemical information encoded in electron density and other ingredients used in semilocal functionals.This information is usually looked at from the functional point of view:the exchan...In this perspective,we review the chemical information encoded in electron density and other ingredients used in semilocal functionals.This information is usually looked at from the functional point of view:the exchange density or the enhancement factor are discussed in terms of the reduced density gradient.However,what parts of a molecule do these 3D functions represent? We look atthese quantities in real space,aiming to understand the electronic structure information they encode and provide an insight from the quantum chemical topology(QCT).Generalized gradient approximations(GGAs) provide information about the presence of chemical interactions,whereas meta-GGAs can differentiate between the different bonding types.By merging these two techniques,we show new insight into the failures of semilocal functionals owing to three main errors:fractional charges,fractional spins,and non-covalent interactions.We build on simple models.We also analyze the delocalization error in hydrogen chains,showing the ability of QCT to reveal the delocalization error introduced by semilocal functionals.Then,we show how the analysis of localization can help understand the fractional spin error in alkali atoms,and how it can be used to correct it.Finally,we show that the poor description of GGAs of isodesmic reactions in alkanes is due to 1,3-interactions.展开更多
为研究飞秒脉冲激光冲击强化中等离子体压力时空演化规律,利用考虑电子态密度(DOS)效应的模型计算了电子热容和电声耦合系数随电子温度的演化规律,并与采用QEOS(quotidian equation of state)模型计算结果进行了对比;提出DOS飞秒脉冲激...为研究飞秒脉冲激光冲击强化中等离子体压力时空演化规律,利用考虑电子态密度(DOS)效应的模型计算了电子热容和电声耦合系数随电子温度的演化规律,并与采用QEOS(quotidian equation of state)模型计算结果进行了对比;提出DOS飞秒脉冲激光冲击强化模型,计算得到电子温度、晶格温度、等离子体羽位置时间演化规律和等离子体压力时空演化规律,并与QEOS飞秒脉冲激光冲击强化模型结果进行了对比。结果表明:DOS飞秒脉冲激光冲击强化模型计算得到的等离子体羽位置随时间的演化规律与实验结果吻合程度更好;增加激光能量或功率密度、考虑电子DOS效应会增加电子、晶格温度和等离子体压力。展开更多
为了研究金属掺杂团簇时带隙的变化趋势,本文用Cr,Mo,V,Nb四种元素掺杂(TiO_2)_3团簇,并用密度泛函理论下的广义梯度近似(GGA)方法计算.不同掺杂位置的结果表明最好的掺杂位置是3-配位的钛位置.所有掺杂后(TiO_2)_3团簇的HOMO-LUMO带隙...为了研究金属掺杂团簇时带隙的变化趋势,本文用Cr,Mo,V,Nb四种元素掺杂(TiO_2)_3团簇,并用密度泛函理论下的广义梯度近似(GGA)方法计算.不同掺杂位置的结果表明最好的掺杂位置是3-配位的钛位置.所有掺杂后(TiO_2)_3团簇的HOMO-LUMO带隙都要比未掺杂时要小,对应高能区态密度峰值左移0.1 e V;HOMO的电子云分布主要占据了氧原子的位置,当掺杂团簇被激发时,电子从末端氧原子位置跃迁到掺杂原子.此外,我们进一步的计算表明Cr和Mo是降低(TiO_2)_3团簇带隙较好的掺杂元素.为了进一步的研究掺杂(TiO_2)_3团簇的性质以及它在光催化,清洁能源等方面的应用,还需要我们进行实验和理论相结合的研究.展开更多
基金supported partially by the Framework of CALSIMLAB under the Public Grant ANR-11-LABX-0037-01 Overseen by the French National Research Agency(ANR) as Part of the "Investissements d’Avenir" Program(reference:ANR-11-IDEX-0004-02)the National Science Foundation(CHE-1362927)the National Institute of Health(R01-GM061870),USA
文摘In this perspective,we review the chemical information encoded in electron density and other ingredients used in semilocal functionals.This information is usually looked at from the functional point of view:the exchange density or the enhancement factor are discussed in terms of the reduced density gradient.However,what parts of a molecule do these 3D functions represent? We look atthese quantities in real space,aiming to understand the electronic structure information they encode and provide an insight from the quantum chemical topology(QCT).Generalized gradient approximations(GGAs) provide information about the presence of chemical interactions,whereas meta-GGAs can differentiate between the different bonding types.By merging these two techniques,we show new insight into the failures of semilocal functionals owing to three main errors:fractional charges,fractional spins,and non-covalent interactions.We build on simple models.We also analyze the delocalization error in hydrogen chains,showing the ability of QCT to reveal the delocalization error introduced by semilocal functionals.Then,we show how the analysis of localization can help understand the fractional spin error in alkali atoms,and how it can be used to correct it.Finally,we show that the poor description of GGAs of isodesmic reactions in alkanes is due to 1,3-interactions.
文摘为研究飞秒脉冲激光冲击强化中等离子体压力时空演化规律,利用考虑电子态密度(DOS)效应的模型计算了电子热容和电声耦合系数随电子温度的演化规律,并与采用QEOS(quotidian equation of state)模型计算结果进行了对比;提出DOS飞秒脉冲激光冲击强化模型,计算得到电子温度、晶格温度、等离子体羽位置时间演化规律和等离子体压力时空演化规律,并与QEOS飞秒脉冲激光冲击强化模型结果进行了对比。结果表明:DOS飞秒脉冲激光冲击强化模型计算得到的等离子体羽位置随时间的演化规律与实验结果吻合程度更好;增加激光能量或功率密度、考虑电子DOS效应会增加电子、晶格温度和等离子体压力。
基金supported by the National Natural Science Foundation of China(20903075,21273172)Program of Introducing Talents of Discipline to Universities,China(111 Project)(B08040)Northwestern Polytechnical University Foundation for Fundamental Research,China(JC20100226)~~
文摘为了研究金属掺杂团簇时带隙的变化趋势,本文用Cr,Mo,V,Nb四种元素掺杂(TiO_2)_3团簇,并用密度泛函理论下的广义梯度近似(GGA)方法计算.不同掺杂位置的结果表明最好的掺杂位置是3-配位的钛位置.所有掺杂后(TiO_2)_3团簇的HOMO-LUMO带隙都要比未掺杂时要小,对应高能区态密度峰值左移0.1 e V;HOMO的电子云分布主要占据了氧原子的位置,当掺杂团簇被激发时,电子从末端氧原子位置跃迁到掺杂原子.此外,我们进一步的计算表明Cr和Mo是降低(TiO_2)_3团簇带隙较好的掺杂元素.为了进一步的研究掺杂(TiO_2)_3团簇的性质以及它在光催化,清洁能源等方面的应用,还需要我们进行实验和理论相结合的研究.
