La,Ca改性及缺陷PbTiO3纳米晶的DFT—DVM计算研究

采用ＤＦＴ－ＤＶＭ计算程序中的原子簇模型对Ｌａ，Ｃａ改性及含有缺陷的Ｌａ，Ｃａ改性ＰｂＴｉＯ３纳米晶进行了量子化学计算，得到了晶体中的电荷分布规律、总能、总态密度及轨道能级，并对晶体的成键情况进行了分析。     

Cell Volume Effect on the Ferroelectric Stability of Perovskite Oxides PbTiO3 and BaTiO3 from First Principle Calculation

Electronic structure of ferroelectric PbTiO3 and BaTiO3 is calculated by the full potential linearized augmented plane wave method. The total energy as a function of the displacement of Ti-cation is obtained for PbTiO3 and BaTiO3 at different cell volumes. At experimental cell volume, Ti-displacement lowers the total energy and the ferroelectricity is stable. When the cell volume is reduced to 90%, total energy is increased with Ti-displacement and ferroelectricity will disappear. The cell volume effect is also confirmed by comparison of the density of states of Ti and O at different cell volumes.     

纳米PbTiO3改性MnO2电极

改性添加剂;放电容量;纳米PbTiO3改性MnO2电极     

给、吸电子基团对芳香共轭体系电子结构影响的密度泛函理论研究

采用密度泛函理论,在B3LYP／6—31G^＊方法水平上对8个连接有给、吸电子基团的芳香共轭体系的稳定性、偶极矩、静电荷分布和前线轨道能级进行了研究,并采用TD／DFT方法进一步研究了它们的电子光谱．结果表明a-1,b-1,c-1和d-2分子比它们的同分异构体要稳定;对于苯、呋喃、吡咯与乙烯形成的共轭体系,吸电子基团连接在乙烯一端,给电子基团连接在芳香环上使体系的偶极距增强,而吡啶则相反;前线轨道能级差较小的是吸电子基团连接在芳香环一端的体系,相应的分子最大吸收波长也较大．     

电场和应力作用下氮钝化扶手型氧化锌纳米带的电子结构和磁特性

采用密度泛函理论(DFT)方法,在LDA+U水平下详细研究了电场和应力作用下氮钝化扶手型氧化锌纳米带(NA8-ZnONRs)的电子结构和磁特性。对体系的电子结构和磁性进行详细的计算,结果表明：本征扶手型氧化锌纳米带(A8-ZnONRs)是无磁性P型半导体。氮钝化后NA8-ZnONRs具有铁磁金属性,其磁性主要来源于N2p轨道(2.56μ_B)和O2p轨道(0.69μ_B)电子的自旋极化,总磁矩为3.21μ_B。NA8-ZnONRs体系对X方向电场有较强的响应,通过调节X方向电场的幅度,可以有效调节体系的磁矩。在X方向电场作用下体系仍具有铁磁金属性,磁性也主要来源于N2p和O2p轨道电子的自旋极化。施加X方向应力作用后,体系仍表现为铁磁金属性。与NA8-ZnONRs纳米带磁矩相比,体系的总磁矩均发生了较大幅度的增长,表明体系对应力作用具有较明显的相应。但随着应力幅度的调节,总磁矩的变化较平坦。表明施加应力可以有效调节体系的磁矩,但在较小应力范围内,体系对应力变化的相应不明显。     

富勒烯C70及Sc3N@C70的密度泛函理论研究

在混合密度泛函B3LYP理论下,用6-31G*基函数对富勒烯C70、它的阴离子及内掺Sc3N富勒烯Sc3N@C70两种同分异构体的几何结构和电子结构进行了研究。计算结果表明,在C70的两种异构体中,满足五元环分离规则(IPR)的C70(D5h)稳定,C70q-(#7854)(q=4,6)比C70q-(D5h)稳定;在Sc3N@C70两种异构体中有三对两两相邻五元环的Sc3N@C70(#7854)稳定,C70(#7854)易于形成富勒烯金属包合物。     

Nd2O3改性PbTiO3陶瓷性能的研究

通过添加少量的Ｎｄ２Ｏ３可以改善ＰｂＴｉＯ３陶瓷的性能。这种性能的改善是与用Ｎｄ２Ｏ３改性的ＰｂＴｉＯ３陶瓷的显微结构物导电机制密切相关的。本文研究了Ｎｄ２Ｏ３改性的ＰｂＴｉＯ３陶瓷的性能参数。     

Ge@C82结构及性质的理论研究

采用密度泛函理论方法,对Ge@C82的结构及性质进行计算研究.结果表明,由于包合Ge,C82碳笼平均键长增长,碳笼增大,而且Ge原子略微偏离碳笼中心.三重态的C2Ge@C82为能量最低结构.自然布居分析表明,C2C82与Ge之间未发生电子转移,可以用C2Ge@C82来表示它的结构.C2C82和C2Ge@C82的红外光谱计算结果显示,二者的主要区别为C2Ge@C82在1100～1200 cm-1区间的吸收峰变得更尖锐.     

有机-无机杂化化合物[Cu（μ-cbdca）（H2O）]n的电子结构及铁磁性

利用基于密度泛函理论(DVF)的第一性原理的FP_LAPW方法,对以铜离子为磁性中心的化合物[Cu(μ-cbdca)(H2O)]n(cbdca=cyclobutanedicarboxylate)的电子结构及磁性质进行了计算.对该材料的铁磁性、反铁磁性和非磁性三种状态下的总能量进行了计算.计算结果表明,[Cu(μ-cbdca)(H2O)]n的铁磁态能量最低,该化合物为稳定的铁磁性物质,该结果与实验吻合较好.对原子磁矩的计算结果发现,铜原子对化合物磁性的贡献较大,双齿配体上的氧原子和碳原子的贡献相对较小.     

CdO及CdxZn1-xO化合物的结构、能量和电子性能分析

采用基于密度泛函理论的第一性原理的平面波超软赝势计算方法,研究了纤锌矿结构的cdxZn1-xO化合物以及CdO在纤锌矿结构、岩盐结构和闪锌矿结构的基态电子特性和体结构,分析了CdO的稳定性.通过对比纤锌矿结构、岩盐结构和闪锌矿结构CdO的内聚能,发现岩盐结构和纤锌矿结构CdO的稳定性好,闪锌矿结构相对较差;通过对CdxZn1-xO化合物在不同Cd组分下的电子结构计算,得到了较好的禁带宽度拟合结果,能带弯曲参量B=1.02 eV;通过形成能与组分关系的分析,我们认为当Cd的组分x=0.4左右时,CdxZn1-xO化合物最不稳定,容易出现相分离现象.     

Theoretical Study of La , Ca modified and Pure PbTiO_3 Nanocrystals

ＩｎｔｒｏｄｕｃｔｉｏｎＢｏｔｈｔｈｅｓｔｕｄｉｅｓｏｎｔｈｅｌｏｗ－ｄｉｍｅｎｓｉｏｎｍａｔｅｒｉａｌｓｏｆｍｏｄｉｆｉｅｄＰｂＴｉＯ３ａｎｄｐｕｒｅＰｂＴｉＯ３ｗｅｒｅｃａｒｒｉｅｄｏｕｔｓｙｎｃｈｒｏｎｏｕｓｌｙ，ｔｈｅａｕｔｈｏｒｓｈｏｐｅｄｔｏｓｔｒｅｎｇｔｈｅｎｔｈｅｐｈｙｓｉｃｏｃｈｅｍｉｃａｌｐｒｏｐｅｒ－ｔｉｅｓｏｆｔｈｅｍａｔｅｒｉａｌｓｉｎｓｏｍｅｒｅｓｐｅｃｔｓｂｙｍｅａｎｓｏｆｃｈａｎｇｉｎｇｄｅｓｉｇｎｍｏｄｉｆｉｃａｔｉｏｎｓｃｈｅｍｅ．Ａｍｏｎｇｔｈｅｎｕｍｅｒｏ…     

First-principles Study on the Electronic and Bonding Properties of PbTiO3 (110) Polar Terminations

The electronic structures and bonding properties of the (110) polar terminations of cubic PbTiO₃ were examined by the first-principles calculations at the generalized gradient approximation level. Two stoichiometric (PbTiO and O₂) and three nonstoichiometric(TiO, Pb, and O) terminations were considered in this study. With the aid of the calculated electron density differences, atomic charges, band structures, and densities of states, the charge redistributions and electronic properties were evaluated in detail. Furthermore, based on the calculated results of the cleavage energies, relaxation energies, and surface energies of the investigated terminations, the charge compensation by the modification of the surface stoichiometry and the fillings of surface states were thermodynamically evaluated.     

H‐doped PbTiO3: Structure and electronic properties

The geometry and electronic properties of the interstitial H atom in the tetragonal PbTiO₃ crystal have been studied using an advanced quantum chemical computer code developed for the modeling of crystals. The inserted H atom was found to bind to one of the O atoms and to form the hydroxyl, O? H group, with the inter‐atomic distance equal to 0.93 Å and 1.00 Å for the hydroxyls containing O atom in the dimerized and nondimerized Ti? O? Ti chains, respectively. Atomic displacements in the vicinity of O? H complex are calculated and analyzed in relation to the H‐produced changes upon the atomic charges in defective region. The role of H impurity on the ferroelectric polarization in the tetragonal PbTiO₃ is discussed in terms of the results obtained in our research and those presented in the other studies on this subject. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007     

Au@Gen (n=2-9)团簇的几何结构和电子性质的理论研究

本文选用密度泛函B3LYP方法在Lan L2DZ基组上对Au Gen+(n=2~9)团簇的几何结构和电子性质进行了理论研究,其中包括结构优化、平均键能、HOMO-LUMO能隙和电荷转移等。结果表明,随着锗原子数的不断增加,这些掺杂团簇逐渐形成了三维立体结构,并发现Au Ge7+和Au Ge9+两个掺杂团簇是相对稳定的,而且这些掺杂团簇的电荷转移主要是由金原子到锗原子骨架上。此外,还模拟了这些掺杂团簇的红外光谱,为以后实验研究提供有价值的理论参考。     

A Raman Scattering Study of PbTiO3 and TiO2 Obtained by Sol-Gel

The mechanisms that give rise to the broadening and the shifts of the Raman peaks of titanium dioxide and lead titanate nanocrystals prepared by sol-gel are discussed. Phonon confinement and oxygen deficiency are competitive mechanisms in TiO2 obtained by different sol-gel preparations whereas pressure effects on the nanocrystals predominate in ferroelectric PbTiO3.     

The Solgel Preparation and Electric Properties of MnO2-doped PbTiO3 Ceramics

ＴｈｅＳｏｌ┐ｇｅｌＰｒｅｐａｒａｔｉｏｎａｎｄＥｌｅｃｔｒｉｃＰｒｏｐｅｒｔｉｅｓｏｆＭｎＯ２┐ｄｏｐｅｄＰｂＴｉＯ３ＣｅｒａｍｉｃｓＱＩＡＮＧＬｉａｎｇ－ｓｈｅｎｇ＊,ＦＵＨｏｎｇ－ｇａｎｇ＊＊ａｎｄＸＵＣｈｏｎｇ－ｑｕａｎ（Ｄｅｐａｒｔｍｅｎｔ...     

第一性原理计算钛酸铅A位掺杂对其负热膨胀性的影响

近年来,实验发现钛酸铅基材料具有负热膨胀性,且其热膨胀程度会受到掺杂元素的影响.目前所研究的A位掺杂体系中,仅Cd原子掺杂能使钛酸铅负热膨胀性增强.所以研究A位掺杂钛酸铅,比较Cd原子与其他原子在掺杂钛酸铅时化学键的异同,有助于深刻理解钛酸铅负热膨胀的本质.本文利用第一性原理,分别优化了Sr、Ba、Cd掺杂钛酸铅的晶格常数,计算了它们的态密度和电荷密度.结果表明Cd―O键的共价性强于Pb―O键,而Ba―O键和Sr―O键几乎呈离子性,Ba/Sr对Pb的替代削弱了化合物的共价性,降低了自发极化强度.与实验测量的热膨胀系数对比可以发现,A位原子与氧原子之间的共价性增强,化合物负热膨胀程度升高;若A位原子与氧原子之间的共价性削弱,负热膨胀程度降低.可见A位原子与氧原子之间的共价性影响了钛酸铅基化合物负热膨胀性.     

Theoretical Study on the Structure and Isomerization of CH_3SB

1 INTRODUCTION Solid boron and materials containing boron are po-tential excellent rocket fuel. Many studies arefocused in experiment and theory on the boroncompounds, among which simple boroncompound-HOB with simple structure can be readilyprepared. There are many reports on the experimentaland theoretical re- search results of the molecule aswell as unsaturated CH3NH=B and H2N=B exceptHOB. Very recently, some theoretical studies ofunsaturated CH3OB…     

BaTiO3纳米晶的合成与表征

以硬脂酸、硬脂酸钡和钛酸丁酯为原料合成了ＢａＴｉＯ３纳米晶，粒度为１０～２０ｎｍ，烧成温度为６５０℃，低于传统的合成温度。用红外光谱、差热分析、热重分析和Ｘ射线衍射对合成过程进行了研究，用透射电镜考察纳米晶的粒度和形貌。用发射光谱和Ｘ射线荧光光谱对样品纯度进行了分析。结果表明，此法合成的纳米晶ＢａＴｉＯ３纯度高、粒度小且较均匀，在常温下属立方钙钛矿型。     

水溶性染料在PbTiO3体系中的光催化降解

以ＰｂＴｉＯ３为光催化剂，对多种水溶性染料的光催化降解反应进行了研究，结果表明：光降解脱色效率与染料溶液匠ＰＨ值、光照时间、光源种类及催化剂用量等因素有关，染料浓度为１０ｍｇ／ＬＰＨ＝６，催化剂用量为１００ｍｇ／５０ｍｌ，直接以太阳光作光源，光照１ｈ以后，脱色率达９０５以上，有机染料中硫和氮元素转化为ＳＯ４＾２－和ＮＯ３的生成率分别为８５％和６５％。