ThMn12型金属间化合物YFe10-xSix有序化行为的热力学研究

采用四亚晶格热力学模型,辅助以第一性原理总能计算,研究了具有ThMn12原型结构的YFe10-xSix金属间化合物中元素的占位有序化行为.结果表明,YFe10.2Si1.8和YFe10Si2化合物中稀土元素Y占据2a亚晶格,Fe占据全部8i亚晶格和部分8j,8f亚晶格,Si占据部分8j,8f亚晶格,且Si更倾向于占据8f亚晶格.随温度的变化,YFe10-xSix化合物中各元素的占位有序化行为并不发生改变.本文预测结果与近期文献报道的实验结果相当吻合,间接证明了成分为YFe10Si2的化合物以ThMn12型结构的YFe10.2Si1.8相和α-(Fe,Si)固溶体相的共存形式更为合理.     

稀土过渡金属CaCu5型衍生化合物结构的原子级模拟

稀土过渡族金属化合物是功能材料研究领域的重要对象. 本文综述了CaCu5衍生型稀土过渡金属化合物Rn-mM5n 2m结构和变换关系的传统内容、含义, 以及在应用中的有效性和局限性. 从原子间相互作用势出发, 通过能量最小化对5类二元本征结构SmFe5, Sm2Fe17(H), Sm2Fe17(R), SmFe12(t), Sm3Fe29的空间群及晶格参数进行了计算, 并由此确定了这5类结构间的变换矩阵, 与传统矩阵变换关系作了对照, 分析了它们相近和相异的原因. 讨论了第三元素Cr, Ti对Sm3Fe29结构的稳定作用, 以及对晶体几何参数及X光谱的影响, 这都是传统矩阵变换反映不了的.     

C60分子间相互作用的Morse势函数及应用

利用C60晶体的升华焓、晶胞参数等性质,得到C60分子间相互作用的Morse势函数，其解析表达式为 u(r)=30.05 exp[－24.96(r－1.005)]－60.10 exp[－12.48(r－1.005)] 采用该作用势研究了C60及其晶体的一些性质, 如计算得到C60晶体(100)面的表面能为7.46×10－2 J•m－2, 在650～4500 K温度范围内计算了C60分子的第二维里系数, 研究了C60面心立方晶体的晶格振动, 并计算得到了晶格振动的态密度分布,还利用该作用势研究了不同晶型时C60晶体的稳定性.     

1,1-二氟乙烷和1,2-二氟乙烷分子内原子间非键相互作用

用从头算势诱导极小二乘拟合(PD/LSF)和(exp-6-1)函数研究了1,1-二氟乙烷和1,2-二氟乙烷分子内非键原子间的相互作用。计算结果表明, 同分异构体的能量稳定性差, 在于分子内非键原子间的相互作用。该模式提供了一种简单、实用的研究分子内非键相互作用的方法。     

原子氧在Ru低指数面及(1120), (1121)台阶面上的吸附

利用原子与表面簇合物相互作用的5参数Morse势方法(简称5-MP)系统地研究了O-Ru低指数面及Ru(1120), (1121)台阶面体系, 获得了吸附几何、结合能、振动频率等临界点特性, 所得相关数据与实验结果非常吻合. 并且通过理论计算及原子吸附态振动指纹的遗传、遗变特性预言了氧原子在Ru(1121)台阶面的吸附. 本文认为氧原子在HCP晶格的金属表面上的吸附倾向于三重位.     

原子氧在Ru低指数面及(110),(111)台阶面上的吸附

利用原子与表面簇合物相互作用的5参数Morse势方法(简称5-MP)系统地研究了O-Ru低指数面及Ru(1120),(1121)台阶面体系,获得了吸附几何、结合能、振动频率等临界点特性,所得相关数据与实验结果非常吻合.并且通过理论计算及原子吸附态振动指纹的遗传、遗变特性预言了氧原子在Ru(1121)台阶面的吸附.本文认为氧原子在HCP晶格的金属表面上的吸附倾向于三重位.     

A2BC60和A3C60晶体中的短程相互作用

研究了Ａ３Ｃ６０和Ａ２ＢＣ６０晶体的结构和稳定性。计算了它们的Ｍａｄｅｌｕｎｇ常数、结合能、晶格常数和体积弹性模量,并讨论了晶体中的短程相互作用。结果显示,短程相互作用结构和八面体空隙碱金属的稳定性具有极大的影响。ＣｓＫ２Ｃ６０、ＲｂＫ２Ｃ６０和Ｋ３Ｃ６０的晶格常数计算结果与实验测量值非常符合。     

两体扰动势和H2O通道反应的三原子体系解析势

提出了两体扰动势的概念.通过两体扰动势构造多原子相互作用体系解析势的理论方法,获得了非线性三原子H2O相互作用体系的解析势函数.用势能面正确描述了O（1D）＋H2→H2O→OH＋H通道反应的性质.理论分析和实验结果非常符合.该方法比较容易推广构造多原子相互作用体系解析势.     

两体扰动势和H2O通道反应的三原子体系解析势

提出了两体扰动势的概念.通过两体扰动势构造多原子相互作用体系解析势的理论方法,获得了非线性三原子H2O相互作用体系的解析势函数.用势能面正确描述了O(1D)+H2→H2O→OH+H通道反应的性质.理论分析和实验结果非常符合.该方法比较容易推广构造多原子相互作用体系解析势.     

立方面心C60晶体晶格振动的研究

采用C60分子之间相互作用势的Kihra形式,研究了立方面心C60晶体的晶格振动问题,得到了质心振动沿[111]、[110]及[100]方向的声子散射圆频率分布曲线及C60晶格振动频率的态密度分布.采用所得到的C60晶格振动频率的态密度分布,计算了晶体C60在298 K时的等压热容,所得数值与实验值相符.     

Sc2MgGa2 and Y2MgGa2

Scandium magnesium gallide, Sc₂MgGa₂, and yttrium magnesium gallide, Y₂MgGa₂, were synthesized from the corresponding elements by heating under an argon atmosphere in an induction furnace. These intermetallic compounds crystallize in the tetragonal Mo₂FeB₂‐type structure. All three crystallographically unique atoms occupy special positions and the site symmetries of (Sc/Y, Ga) and Mg are m2m and 4/m, respectively. The coordinations around Sc/Y, Mg and Ga are pentagonal (Sc/Y), tetragonal (Mg) and triangular (Ga) prisms, with four (Mg) or three (Ga) additional capping atoms leading to the coordination numbers [10], [8+4] and [6+3], respectively. The crystal structure of Sc₂MgGa₂ was determined from single‐crystal diffraction intensities and the isostructural Y₂MgGa₂ was identified from powder diffraction data.     

Zur Kenntnis der Dialkalimetalldichalkogenide β-Na2S2, K2S2, α-Rb2S2, β-Rb2S2, K2Se2, Rb2Se2, α-K2Te2, β-K2Te2 und Rb2Te2

On Dialkali Metal Dichalcogenides β-Na₂S₂, K₂S₂, α-Rb₂S₂, β-Rb₂S₂, K₂Se₂, Rb₂Se₂, α-K₂Te₂, β-K₂Te₂ and Rb₂Te₂ The first presentation of pure samples of α- and β-Rb₂S₂, α- and β-K₂Te₂, and Rb₂Te₂ is described. Using single crystals of K₂S₂ and K₂Se₂, received by ammonothermal synthesis, the structure of the Na₂O₂ type and by using single crystals of β-Na₂S₂ and β-K₂Te₂ the Li₂O₂ type structure will be refined. By combined investigations with temperature-dependent Guinier-, neutron diffraction-, thermal analysis, and Raman-spectroscopy the nature of the monotropic phase transition from the Na₂O₂ type to the Li₂O₂ type will be explained by means of the examples α-/β-Na₂S₂ and α-/β-K₂Te₂. A further case of dimorphic condition as well as the monotropic phase transition of α- and β-Rb₂S₂ is presented. The existing areas of the structure fields of the dialkali metal dichalcogenides are limited by the model of the polar covalence.     

Crystal Structures of [Bu2Sn(O2PPh2)2], [Ph2Sn(O2PPh2)2], and [PhClSn(O2PPh2)OMe]2. Raman Spectra of [Ph2Sn(O2PPh2)2] and [PhClSn(O2PPh2)OMe]2

[(n‐Bu)₂Sn(O₂PPh₂)₂] ( 1 ), and [Ph₂Sn(O₂PPh₂)₂] ( 2 ) have been synthesized by the reactions of R₂SnCl₂ (R=n‐Bu, Ph) with HO₂PPh₂ in Methanol. From the reaction of Ph₂SnCl₂ with diphenylphosphinic acid a third product [PhClSn(O₂PPh₂)OMe]₂ ( 3 ) could be isolated. X‐ray diffraction studies show 1 to crystallize in the monoclinic space group P2₁/c with a = 1303.7(1) pm, b = 2286.9(2) pm, c = 1063.1(1) pm, β = 94.383(6)°, and Z = 4. 2 crystallizes triclinic in the space group , the cell parameters being a = 1293.2(2) pm, b = 1478.5(4) pm, c = 1507.2(3) pm, α = 98.86(3)°, β = 109.63(2)°, γ = 114.88(2)°, and Z = 2. Both compounds form arrays of eight‐membered rings (SnOPO)₂ linked at the tin atoms to form chains of infinite length. The dimer 3 consists of a like ring, in which the tin atoms are bridged by methoxo groups. It crystallizes triclinic in space group with a = 946.4(1) pm, b = 963.7(1) pm, c = 1174.2(1) pm, α = 82.495(6)°, β = 66.451(6)°, γ = 74.922(6)°, and Z = 1 for the dimer. The Raman spectra of 2 and 3 are given and discussed.     

Electrochemical study of (NEt4)2Cl2FeS2MoS2 and (NEt4)2Cl2FeS2MoS2FeCl2

Summary The ability of [MoS₄]^2–, anions to be used as ligands for transition metal ions has been widely demonstrated, especially with Fe²⁺. The present study has been restricted to linear complexes such as (NEt₄)₂ [Cl₂FeS₂MoS₂] and (NEt₄)₂[Cl₂FeS₂MoS₂FeCl₂]. Their electrochemical properties are described: upon electrochemical reduction, these compounds yield MoS₂, as a black precipitate, and an iron complex in solution, assumed to be [SFeCl₂]^2–. The electrochemical reduction goes through two electron transfers, coupled with the breakdown of the molecular skeleton: a DISPl and an ECE mechanism. Depending on the solvent, the following equilibrium may be observed: [Cl₄Fe₂MoS₄]^2–[Cl₂FeMoS₄]^2–+FeCl₂. The equilibrium constant, K_D, was evaluated by differential pulse polarography. K_D is tightly related to the donor number of the solvent.     

Syntheses,Spectroscopic Studies,and Crystal Structures of Me2Sn(O2PPh2)2, Ph2Pb(O2PMe2)2, and Ph2Pb(O2PPh2)2

Me₂Sn(O₂PPh₂)₂ ( 1 ), Ph₂Pb(O₂PMe₂)₂ ( 2 ), and Ph₂Pb(O₂PPh₂)₂ ( 3 ) have been synthesized by the reactions of Me₂SnCl₂ or Ph₃PbCl with the corresponding diorganophosphinic acid in methanol. X‐ray diffraction studies show that the diorganophosphinate groups behave as double bridges between the metal atoms leading to polymeric ring‐chain structures with M₂O₄P₂ (M = Pb, Sn) eight‐membered rings. The organic groups bonded to the metal atoms are in trans‐position in the resulting octahedral arrangement around the metal atoms. The IR and the mass spectra were reported and discussed.     

The alkali hypophosphites KH2PO2, RbH2PO2 and CsH2PO2

The structures of the hypophosphites KH₂PO₂ (potassium hypophosphite), RbH₂PO₂ (rubidium hypophosphite) and CsH₂PO₂ (caesium hypophosphite) have been determined by single‐crystal X‐ray diffraction. The structures consist of layers of alkali cations and hypophosphite anions, with the latter bridging four cations within the same layer. The Rb and Cs hypophosphites are isomorphous.     

Thermal decomposition of Me3SnO2PCl2, Me2Sn(O2PCl2)2 and Ph3SnO2PCl2

TG and DTA studies on Me₃SnO₂PCl₂, Me₂Sn(O₂PCl₂)₂ and Ph₃SnO₂PCl₂ were carried out under dynamic argon atmosphere. The results show that the decomposition proceeds in different stages leading to the formation of Sn₃(PO₄)₂ as a stable product. This compound was characterized by IR spectroscopy. Decomposition schemes involving reductive elimination reactions were proposed.