稀土7075铝合金中块状化合物的结构和形成规律

用分析电镜、扫描电镜等手段研究了稀土７０７５铝合金中粗大块状化合物的成分、结构和形成规律。研究表明，在铸态稀土７０７５合金中出现的粗大块状化合物是一种（Ｃｒ，Ｔｉ）２ＲＥ（Ａｌ，Ｘ）２０型稀土化合物，其中Ｘ为Ｍｇ，Ｃｕ，Ｚｎ等元素。该化合物具有体心立方结构，晶体常数为１．４５３－１．４５８ｎｍ，显微硬度为４０００－５６００ＭＰａ，计算密度为３．４ｇ／ｃｍ＾３。合金中（Ｔｉ＋Ｃｒ）含量的减少和凝固时     

稀土对60CrMnMo钢奥氏体长大动力学的影响

研究了不同稀土加入量对６０ＣｒＭｎＭｏ钢奥氏体晶粒长大动力学的影响。结果表明，６０ＣｒＭｎＭｏ钢中加入一定量的稀土，能细化奥氏体晶粒并抑制其长大。根据实验结果，对奥氏体晶界迁移激活能（Ｑ）进行了计算，计算表明随稀土加入量增加，Ｑ值亦增加。     

稀土对铸造Cr12MoV模具钢碳化物形貌及性能的影响

研究了稀土元素对铸造Ｃｒ１２ＭｏＶ模具钢碳化物形貌及性能的影响。实验结果表明，稀土地Ｍ７Ｃ３型共晶碳化物有很强的变质作用，Ｃｒ１２ＭｏＶ模具钢铸态为粗大的网状共生共晶组织，经变质处理，共晶组织细化，离异共昌数量半多；热处理后共晶碳化物粒化且均匀分布，冲击韧性得到了明显提高，耐磨性比锻造Ｃｒ１２ＭｏＶ模具钢高出１倍以上。     

稀土对ZA27合金晶间腐蚀影响的电子理论研究

通过自行开发的计算机软件构造了ZA27合金中α相大角度晶界析出η相及稀土元素的原子集团模型. 采用递归法计算了Al, Zn, La, Y的局域态密度, 计算并分析了α相、η相的总态密度和费米能级, 及稀土对态密度和费米能级的影响. 计算表明: 稀土元素的局域态密度形状与Zn相近, 其与Zn结合的能力大; 稀土元素降低η相的费米能级, 减小Zn, Al电极电位差, 具有抑制晶间腐蚀的作用; 稀土元素不改变α相、η相的总态密度形状, 但使η相的态密度增大, 改变η相的电子结构; 晶格结构对原子的态密度有一定的影响, 掺杂原子的态密度趋于与基体原子态密度相同.     

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。     

SPK势能面上Cl和H2反应的量子动力学计算

给出了在ＳＰＫ势能面上应用广义牛顿变分法（ＧＮＶＰ）和振幅密度衡量法（ＭＭＡＤ）对于反应系统Ｃｌ＋Ｈ２→ＨＣｌ＋Ｈ态－态之间反应几率的三维量子力学计算。总反应能量从９ｋｃａｌ．ｍｏｌ＾－１至１６ｋｃａｌ．ｍｏｌ＾－１。对于两种方法的计算结果进行了比较。为了同超球谐密耦合方法结果进行比较，还对总反应能量１９ｋｃａｌ．ｍｏｌ＾－１的情况进行了计算和分析。     

浇铸尼龙—6的结晶与熔融

用ＤＳＣ法研究了Ｌａ２Ｏ３和Ｙ２Ｏ３对浇铸尼龙－６（ＭＣ尼龙－６）结晶与熔融的影响，二者都使ＭＣ尼龙－６熔体等速降温的结晶温度Ｔｅ升高，等速升温的溶点Ｔｍ降低，结晶度Ｘｃ降低，拉伸过程的断裂能密度及断裂伸长率提高，Ｌａ２Ｏ３使ＭＣ尼龙－６平衡熔点Ｔｍ降低，结晶速率增加，结晶完善程度变差，Ｙ２Ｏ３使ＭＣ尼龙－６的Ｔｍ升高，它可显著改善ＭＣ尼龙－６的耐热性。     

MgH2分子的激发态研究

本文采用ＳＣＦ、ＭＣＳＣＦ、ＳＯＣＩ方法对ＭｇＨ＿２的基态和两个激发态进行了计算研究，预言了各态的平衡几何构型、总能量、偶极矩、电荷分布等性质，并首次报道了各态的振动频率。     

稀土对SiMnCr和SiMnMo结构钢回火脆性的影响

研究了ＳｉＭｎＣｒ钢和ＳｉＭｎＭｏ钢低温回火过程中机械性能的变化。稀土对低温回火时的材料强度没有明显的影响。ＳｉＭｎＣｒ钢和ＳｉＭｎＭｏ钢分别在３５０和４００℃存在ＴＭＥ谷底值；稀土对谷底值的温度虽然没有影响，却可以在一定程度上改善其数值。稀土改善回火脆性是细化晶粒和抑制奥氏体晶界脆化作用的结果。     

晶态C60,K3C60,K6C60的能带计算

本文用紧束缚法的ＥＨＭＯ三维晶体轨道程序进行计算求得了Ｃ６０，Ｋ３Ｃ６０和Ｋ６Ｃ６０的能带结构，并得到了一系列过去未曾见过报导的原子投影态密度、轨道、原子重叠布据、原子电荷、轨道矢量等数据。从这些能带图中可以充分说明三种物质的区别，并可解释Ｋ３Ｃ６０的超导性和Ｃ６０与Ｋ６Ｃ６０的绝缘性。     

Crystal and magnetic structures and magnetic properties of selenate containing natrochalcite, A(I)M(II)2(H3O2)(SeO4)2 where A = Na or K and M = Mn, Co, or Ni

The synthesis of a series of selenate containing natrochalcite, A(I)M(II)(2)(H(3)O(2))(SeO(4))(2) where A = Na or K and M = Mn, Co, or Ni (here labeled as AMH and AMD for the hydrogenated and deuterated compounds, respectively), the X-ray crystal structure determinations from single crystals (Ni) and powder (Mn), magnetic properties, and magnetic structures of the cobalt analogues are reported. The nuclear crystal structures for NaNiH, KNiH, and KMnH are similar to those reported for the cobalt analogues (NaCoH and KCoH) and consist of chains of edge-sharing octahedra (MO(6)) which are connected by H(3)O(2) and SeO(4) to form layers which are in turn bridged by the alkali, in an octahedral coordination site, to form the 3D-framework. The magnetic properties are characterized by antiferromagnetic interaction at high temperatures and antiferromagnetic ordering at low temperatures (NaCoH, 3.5 K; KCoH, 5.9 K; KNiH, 8.5 K; and KMnH, 16 K), except for KNi(2)(H(3)O(2))(SeO(4))(2) which displays a weak ferromagnetic interaction and no long-range ordering above 2 K. The neutron magnetic structures of the cobalt analogues, studied as a function of temperature, are different for the two cobalt salts and also different from all the known magnetic structures of the natrochalcite family. Whereas the magnetic structure of NaCoD has a k = (0, 0, 0), that of KCoD has one consisting of a doubled nuclear cell, k = (0, 0, 1/2). Both compounds have four magnetic sublattices related to the four cobalt atoms of the nuclear unit cell. In NaCoD the moments are in the bc-plane, M(y) = 2.51(2) μ(B) and M(z) = 1.29(4) μ(B), with the major component along the cobalt chain and the resultant moment, 2.83(3) μ(B), making an angle of 27° with the b-axis. The sum of the moments within the cell is zero. For KCoD the moment at each cobalt site has a component along each crystallographic axis, M(x) = 2.40(3), M(y) = 1.03(3), M(z) = 1.59(8) giving a total M = 2.49(3) μ(B). Within one nuclear cell the moments are fully compensated. The moments corresponding to the cobalt atoms of the second nuclear cell comprising the magnetic unit cell are oriented in opposite directions.     

Electronic and Magnetic Structures of New Interstitial Boron Sub-Oxides B12O2:X (X = B,C, N,O)

The boron-rich boron sub-oxide rhombohedral B₆O considered in B₁₂O₂ full formulation has a large O-O spacing of ~3 Å and a central vacant position that can receive interstitial atoms X, forming a central O-X-O alignment in the dodecaboron cage as observed in well-known triatomic B₁₂ compounds as B₁₂{C-C-C}, B₁₂{N-B-N}, etc. Plane wave density functional theory (DFT) based calculations of unrestricted geometry relaxation of B₁₂{O-X-O}, X = B, C, N, and O let one identify new ternary sub-oxides, all found cohesive while showing different d(X-O) distances ranging from d(B-O) = 1.95 Å down to d(O-O) = 1.73 Å with intermediate d(C-O) = 1.88 Å. The different magnitudes were assigned to the chemical affinities of X-inserts versus host oxygen with the increasing development of X-O bonding along the series with larger cohesive B₁₂{O-O-O}. From the atom projected charge density, B presents none, while significant magnitudes are shown on C and N, the latter developing bonding with terminal oxygen atoms especially N. The presence of unpaired valence electrons leaves nonbonding charge density on X = C, N interstitial compounds, which, besides the relative isolation of the central C and N lead to the onset of magnetic moments: M(C) = 1.9 μ_B, and M(N) = 1 μ_B in a ferromagnetic ground state. Atom-resolved assessments are provided with the magnetic charge density and electron localization function electron localization function (ELF) projections on one hand and the site and spin projected density of states and the chemical bonding based on the overlap integral S_ij within the COOP criterion, on the other hand.     

Magnetic properties and magnetic structures of synthetic natrochalcites, NaM(II)2(D3O2)(MoO4)2, M = Co or Ni

The magnetic properties and magnetic structures from neutron diffraction of two synthetic natrochalcites, NaM(II)2(H3O2)(MoO4)2, M = Co (1Co) or Ni (2Ni), are reported. They are isostructural (monoclinic C2/m) and consist of chains of edge-shared MO6 octahedra connected by mu-O from H3O2(-) and MoO4(2-). These chains form a three-dimensional network with O-H-O, O-Mo-O, and O-Na-O bridging 4, 3, and 4 metal ions, respectively. Both compounds behave as canted antiferromagnets but differ in their behaviors, 1Co showing a broad maximum (28 K) above the Neel transition (21 K) and the canting taking place at 13 K, some 8 K below T(N), while for 2Ni the canting takes place at T(N) (28 K). Analyses of the neutron powder diffraction data shed some light on the geometry of D3O2(-) and suggest antiferromagnetism with a propagation vector k = (0,0,0) with the moments within each chain being parallel but antiparallel to those in neighboring chains. The difference between 1Co and 2Ni is in the orientation of the moments; they are parallel to the chain axis (b-axis) for 1Co and perpendicular to it for 2Ni with a major component along the c-axis and a small one along the a-axis. The heat capacity data peak at 20.9(3) K (1Co) and 25.1(1) K (2Ni). The derived magnetic entropies, following correction of the lattice contribution using the measured data for the nonmagnetic Zn analogue, suggest S = 1/2 for 1Co but is lower than that expected for 2Ni (S = 1). In both cases, only ca. 60% of the entropy is found below the magnetic ordering temperature, suggesting considerable short-range correlations at higher temperatures. While the temperature at which the magnetic diffraction becomes observable coincides with that of at the peak in heat capacity, it is lower than T(N) observed by magnetization measurements in both cases, and there is evidence of short-range ordering in a narrow range of temperature (T(N) +/- 5 K).     

Direct observation of magnetic ordering in the (CH3NH2)K3C60 fulleride

The zero-field muon-spin-relaxation (ZF-micro(+)SR) technique provides direct observation of the development of antiferromagnetic long range order in the hyperexpanded methylaminated fulleride salt, (CH(3)NH(2))K(3)C(60) below T(N) approximately 10 K-coherent ordering of the electronic magnetic moments leads to a local field of approximately 25 G at the muon site at 1.2 K.     

Synthesis, structural, and magnetic characterization of linear and bent geometry cobalt(II) and nickel(II) amido complexes: evidence of very large spin-orbit coupling effects in rigorously linear coordinated Co2+

The complexes M(II){N(H)Ar(Pr(i)(6))}(2) (M = Co, 1 or Ni, 2; Ar(Pr(i)(6)) = C(6)H(3)-2,6(C(6)H(2)-2,4,6-Pr(i)(3))(2)), which have rigorously linear, N-M-N = 180°, metal coordination, and M(II){N(H)Ar(Me(6))}(2) (M = Co, 3 or Ni, 4; Ar(Me(6)) = C(6)H(3)-2,6(C(6)H(2)-2,4,6-Me(3))(2)), which have bent, N-Co-N = 144.1(4)°, and N-Ni-N = 154.60(14)°, metal coordination, were synthesized and characterized to study the effects of the metal coordination geometries on their magnetic properties. The magnetometry studies show that the linear cobalt(II) species 1 has a very high ambient temperature moment of about 6.2 μ(B) (cf. spin only value = 3.87 μ(B)) whereas the bent cobalt species 3 had a lower μ(B) value of about 4.7 μ(B). In contrast, both the linear and the bent nickel complexes 2 and 4 have magnetic moments near 3.0 μ(B) at ambient temperatures, which is close to the spin only value of 2.83 μ(B). The studies suggest that in the linear cobalt species 1 there is a very strong enhanced spin orbital coupling which leads to magnetic moments that broach the free ion value of 6.63 μ(B) probably as a result of the relatively weak ligand field and its rigorously linear coordination. For the linear nickel species 2, however, the expected strong first order orbital angular momentum contribution does not occur (cf. free ion value 5.6 μ(B)) possibly because of π bonding effects involving the nitrogen p orbitals and the d(xz) and d(yz) orbitals (whose degeneracy is lifted in the C(2h) local symmetry of the Ni{N(H)C(ipso)}(2) array) which quench the orbital angular momentum.     

Stern-Gerlach experiments of one-dimensional metal-benzene sandwich clusters: Mn(C6H6)m (M = Al, Sc, Ti, and V)

A molecular beam of multilayer metal-benzene organometallic clusters Mn(C6H6)m (M = Al, Sc, Ti, and V) was produced by a laser vaporization synthesis method, and their magnetic deflections were measured. Multidecker sandwich clusters of transition-metal atoms and benzene Scn(C6H6)n+1 (n = 1, 2) and Vn(C6H6)n+1 (n = 1-4) possess magnetic moments that increase monotonously with n. The magnetic moments of Al(C6H6), Scn(C6H6)n+1, and Vn(C6H6)n+1 are smaller than that of their spin-only values as a result of intracluster spin relaxation, an effect that depends on the orbital angular momenta and bonding characters of the orbitals containing electron spin. While Ti(C6H6)2 was found to be nonmagnetic, Tin(C6H6)n+1 (n = 2, 3) possess nonzero magnetic moments. The mechanism of ferromagnetic spin ordering in M2(C6H6)3 (M = Sc, Ti, V) is discussed qualitatively in terms of molecular orbital analysis. These sandwich species represent a new class of one-dimensional molecular magnets in which the transition-metal atoms are formally zerovalent.     

1,2,3-triazolate-bridged tetradecametallic transition metal clusters [M14(L)6O6(OMe)18X6] (M=FeIII, CrIII and VIII/IV) and related compounds: ground-state spins ranging from S=0 to S=25 and spin-enhanced magnetocaloric effect

We report the synthesis, by solvothermal methods, of the tetradecametallic cluster complexes [M14(L)6O6(OMe)18Cl6] (M=FeIII, CrIII) and [V14(L)6O6(OMe)18Cl6-xOx] (L=anion of 1,2,3-triazole or derivative). Crystal structure data are reported for the {M14} complexes [Fe14(C2H2N3)6O6(OMe)18Cl6], [Cr14(bta)6O6(OMe)18Cl6] (btaH=benzotriazole), [V14O6(Me2bta)6(OMe)18Cl6-xOx] [Me2btaH=5,6-Me2-benzotriazole; eight metal sites are VIII, the remainder are disordered between {VIII-Cl}2+ and {VIV=O}2+] and for the distorted [FeIII14O9(OH)(OMe)8(bta)7(MeOH)5(H2O)Cl8] structure that results from non-solvothermal synthetic methods, highlighting the importance of temperature regime in cluster synthesis. Magnetic studies reveal the {Fe14} complexes to have ground state electronic spins of S相似文献   

Geometries and magnetisms of the Zr(n) (n=2-8) clusters: the density functional investigations

The geometries, stabilities, and electronic and magnetic properties of small-sized Zr(n) (n=2-8) clusters with different spin configurations were systematically investigated by using density functional approach. Emphasis is placed on studies that focus on the total energies, equilibrium geometries, growth-pattern behaviors, fragmentation energies, and magnetic characteristics of zirconium clusters. The optimized geometries show that the large-sized low-lying Zr(n) (n=5-8) clusters become three-dimensional structures. Particularly, the relative stabilities of Zr(n) clusters in terms of the calculated fragmentation energies and second-order difference of energies are discussed, exhibiting that the magic numbers of stabilities are n=2, 5, and 7 and that the pentagonal bipyramidal D(5h) Zr(7) geometry is the most stable isomer and a nonmagnetic ground state. Furthermore, the investigated magnetic moments confirm that the atomic averaged magnetic moments of the Zr(n) (n not equal to 2) display an odd-even oscillation features and the tetrahedron C(s) Zr(4) structure has the biggest atomic averaged magnetic moment of 1.5 mu(B)/at. In addition, the calculated highest occupied molecular orbital-lowest unoccupied molecular orbital gaps indicate that the Zr(n) (n=2 and 7) clusters have dramatically enhanced chemical stabilities.     

Iodide, azide, and cyanide complexes of (N,C), (N,N), and (N,O) metallacycles of tetra- and pentavalent uranium

In contrast to the neutral macrocycle [UN*(2)(N,C)] (1) [N* = N(SiMe(3))(3); N,C = CH(2)SiMe(2)N(SiMe(3))] which was quite inert toward I(2), the anionic bismetallacycle [NaUN*(N,C)(2)] (2) was readily transformed into the enlarged monometallacycle [UN*(N,N)I] (4) [N,N = (Me(3)Si)NSiMe(2)CH(2)CH(2)SiMe(2)N(SiMe(3))] resulting from C-C coupling of the two CH(2) groups, and [NaUN*(N,O)(2)] (3) [N,O = OC(═CH(2))SiMe(2)N(SiMe(3))], which is devoid of any U-C bond, was oxidized into the U(V) bismetallacycle [Na{UN*(N,O)(2)}(2)(μ-I)] (5). Sodium amalgam reduction of 4 gave the U(III) compound [UN*(N,N)] (6). Addition of MN(3) or MCN to the (N,C), (N,N), and (N,O) metallacycles 1, 4, and 5 led to the formation of the anionic azide or cyanide derivatives M[UN*(2)(N,C)(N(3))] [M = Na, 7a or Na(15-crown-5), 7b], M[UN*(2)(N,C)(CN)] [M = NEt(4), 8a or Na(15-crown-5), 8b or K(18-crown-6), 8c], M[UN*(N,N)(N(3))(2)] [M = Na, 9a or Na(THF)(4), 9b], [NEt(4)][UN*(N,N)(CN)(2)] (10), M[UN*(N,O)(2)(N(3))] [M = Na, 11a or Na(15-crown-5), 11b], M[UN*(N,O)(2)(CN)] [M = NEt(4), 12a or Na(15-crown-5), 12b]. In the presence of excess iodine in THF, the cyanide 12a was converted back into the iodide 5, while the azide 11a was transformed into the neutral U(V) complex [U(N{SiMe(3)}SiMe(2)C{CHI}O)(2)I(THF)] (13). The X-ray crystal structures of 4, 7b, 8a-c, 9b, 10, 12b, and 13 were determined.     

The first homologous series of self-assembled aryl bromo- and aryl cyanocuprates, -argentates,and -aurates; MLi(2)XAr(2) (M = Cu(I), Ag(I), Au(I); X = Br,C(triple bond)N; Ar = [C(6)H(4)CH(2)N(Et)CH(2)CH(2)NEt(2)-2]-)

Reaction of 2 molar equiv of the diamine chelated aryllithium dimers Li(2)(C(6)H(4)[CH(2)N(Et)CH(2)CH(2)NEt(2)]-2)(2) (Li(2)Ar(2)) with the appropriate metal bromide allows the synthesis of the first homologous series of monomeric group 11 bromoate complexes of type MLi(2)BrAr(2) (M = Cu (7), Ag (8), Au (9)). Both in the solid state and in solution, the bromocuprate 7 is isostructural with the bromoargentate 8. The crystal structures of 7 and 8 consist of a MLi(2) core, and each of the two aryl ligands bridges via electron-deficient bonding between the group 11 metal and one Li atom (d(C(ipso)-M) = 1.941(4) (mean) and 2.122(4) (mean) A, for 7 and 8, respectively). The bromine atom exclusively bridges between the two lithium atoms. Each of the ortho-CH(2)N(Et)CH(2)CH(2)NEt(2) moieties is N,N'-chelate bonded to one lithium (d(N-Li) = 2.195(5) and 2.182(0) (mean) A for 7 and 2.154(8) and 2.220(1) (mean) A for 8). Although the MLi(2)BrAr(2) compounds are neutral higher-order -ate species, the structure can also be regarded as consisting of a contact ion pair consisting of two ionic fragments, [Li-Br-Li](+) and [Ar(2)M](-), which are interconnected by both Li-N,N'-chelate bonding and a highly polar C(ipso)-Li interaction. On the basis of NMR and cryoscopic studies, the structural features of the bromoaurate 9 are similar to those of 7 and 8. A multinuclear NMR investigation shows that the bonding between the [Li-Br-Li] and [Ar(2)M] moieties is intermediate between ionic and neutral with an almost equally polarized C(ipso)-Li bond in 7, 8, and 9. Similar reactions between M(C(triple bond)N) and 2 molar equiv of LiAr yield the analogous 2:1 cyanoate complexes of type MLi(2)(C(triple bond)N)Ar(2) (M = Ag (10), Au (11)). Multinuclear NMR studies show that the cyanoate complexes 10 and 11 are isostructural with the bromoate complexes 7, 8, and 9. This paper illustrates that these cyanoaurates may serve as excellent model complexes to gain more insight into the structure of 2:1 cyanocuprates in solution.