核反应堆压力容器模拟钢中富Cu原子团簇的析出与嵌入原子势计算

利用原子探针层析技术(APT)和热处理时效方法,研究了合金元素Ni对核反应堆压力容器模拟钢中富Cu原子团簇析出的影响.实验结果表明,添加合金元素Ni(0.84wt%)的样品中析出富Cu原子团簇的数量密度高于不添加Ni的样品,富Cu原子团簇内以及团簇和基体界面处都有Ni元素的富集现象,这说明合金元素Ni会促使富Cu原子团簇的析出.从多体势的角度出发,利用嵌入原子势理论,基于纯金属元素Fe,Cu,Ni的多体势参数,建立了Fe-Cu二元和Fe-Cu-Ni三元体系的嵌入原子多体势.计算结果表明,当模拟合金中存在1at%Ni时有利于富Cu原子团簇的析出,这与实验结果相符.     

预退火时间对Fe_(80.8)B_(10)P_8Cu_(1.2)非晶合金微结构及磁性能的影响

研究了预退火时间对Fe_(80.8)B_(10)P_8Cu_(1.2)非晶合金微结构及磁性能的影响.穆斯堡尔谱研究表明:在660 K的预退火温度下,随着预退火时间的增加,Fe原子不断富集,非晶基体中的类Fe_3B化学短程有序结构向类Fe B结构转变,并且非晶基体中Fe第一近邻壳层中Cu原子的逐渐脱离以及Fe-P配位键数量的明显减少可间接表征CuP团簇的形成过程.同时,本研究通过调节预退火时间来调控非晶基体中CuP团簇和Fe团簇的数量,促进后续退火晶化过程中α-Fe纳米晶相的析出,并细化纳米晶尺寸,从而获得综合磁性能更加优异的非晶/纳米晶软磁合金.     

高硬导电Cu-Ni-Si系铜合金强化相成分设计

Cu-Ni-Si系铜合金有良好的导电、导热和机械性能,被广泛用于电子元器件等领域.设计Cu-Ni-Si系铜合金成分时,析出相成分的确定是关键.本文利用团簇加连接原子模型方法按"析出相"设计Cu-Ni-Si系铜合金的成分.依据团簇选取准则,选定d-Ni_2Si,γ-Ni_5Si_2和β-Ni_3Si相团簇式分别为[Ni-Ni_8Si_5]Ni,[Si-Ni_(10)]Si_3和[Si-Ni_(12)]Si_3;在基体Cu含量原子分数为93.75%,95%,95.83%,96.7%和97.5%的每一成分点处,分别按析出相δ-Ni_2Si,γ-Ni_5Si_2和β-Ni3Si设计了系列Cu-Ni-Si合金的成分.合金原料在充满氩气的真空电弧炉中熔炼成合金锭,经950°C/1 h固溶水淬和450°C/4 h时效水淬处理.当合金的导电性成为成分设计的主因时,基体Cu含量分别在90%—95.63%和95.63%—97.5%成分区间时,析出相分别按d-Ni_2Si和γ-Ni_5Si_2设计;基体Cu含量大于97.5%,按d-Ni_2Si,γ-Ni_5Si_2或β-Ni3Si中任一相设计均可,导电性基本没有差别.如果合金的强度是成分设计的主因,基体Cu含量分别在90%—93.93%,93.93%—94.34%,94.34%—95.63%和95.63%—96.12%成分区间时,析出相对应于上述成分区间分别按d-Ni_2Si,γ-Ni_5Si_2,β-Ni_3Si和γ-Ni_5Si_2设计;基体Cu含量一旦大于96.12%,析出相按d-Ni_2Si,γ-Ni_5Si_2或β-Ni_3Si中任一相设计均可.     

H_2在Al_(12)X(X=Al,Ni,Cu)团簇表面解离吸附的第一性原理研究

以Ni和Cu原子中心替换的二十面体Al_(12)X(X=Ni、Cu)团簇为基体、采用密度泛函理论系统计算研究了H原子及H_2分子在团簇表面的吸附,并对比了纯Al_(13)团簇对H及H2的吸附,结果表明:相对于纯Al_(13)中H原子的桥位吸附、掺杂团簇Al_(12)X(X=Ni、Cu)中H原子均吸附于团簇顶位;无论是吸附H原子还是H_2分子,Al_(12)Ni的几何结构均发生大的畸变;相较H_2在纯Al_(13)团簇表面的解离吸附,H_2在掺杂团簇Al_(12)X(X=Ni、Cu)表面的解离反应过程中反应能均增大、势垒均降低,这表明掺杂团簇Al_(12)X(X=Ni、Cu)相较纯Al_(13)团簇更有利于H_2解离吸附的发生.     

M_2Ga(M=Cu,Ag,Au)二元合金小团簇的从头算研究(英文)

根据原子与分子反应静力学和群论理论推导出二元合金小团簇M2Ga(M=Cu,Ag,Au)的离解极限和基态电子态.采用量子力学从头算方法及小核实赝势和相应的基组,对二元合金小团簇M2Ga进行几何优化,得到M2Ga基态(2B2)为弯曲平面型结构,并与单元团簇M3(M=Cu,Ag,Au)相似.计算得到合金团簇比单元团簇稳定,其中Au2Ga体系最稳定.同时给出谐振频率、力常数,并且分析得到电子相关效应使得团簇更加紧凑、稳定性增强.     

密度泛函理论研究混合团簇Al12X(X=Sc、Ti、V、Gr、Mn、Fe、Co、Ni、Cu、Zn)的结构和磁性

以四种13原子高对称性(Ih、Oh、D5h、D3h)密堆积结构为初始构型,通过不等价位原子替换,利用密度泛函理论系统研究了Al12 X(X=Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn)掺杂团簇的结构及磁性.结果表明:除Al12 Cr和Al12Fe以外,其它Al12X团簇的基态结构均以Ih替换结构为主,其中前3d元素(X=Sc、Ti、V、Mn)倾向于表面位置替换,而后3d元素(X=Co、Ni、Cu、Zn)则倾向于中心位置替换;Al12 Cr和Al12Fe团簇以Oh结构的表面替换为基态结构;对多数3d元素(X=Ti、V、Cr、Fe、Co、Zn)其掺杂团簇均出现明显的近能同分异构现象;相较纯Al13团簇掺杂团簇普遍体现出磁性增强效应.     

H2在Al12X (X=Al, Ni, Cu)团簇表面解离吸附的第一性原理研究

以Ni和Cu原子中心替换的二十面体Al12X(X=Ni、Cu)团簇为基体、采用密度泛函理论系统计算研究了H原子及H2分子在团簇表面的吸附,并对比了纯Al13团簇对H及H2的吸附,结果表明：相对于纯Al13中H原子的桥位吸附、掺杂团簇Al12X(X=Ni、Cu)中H原子均吸附于团簇顶位;无论是吸附H原子还是H2分子,Al12Ni的几何结构均发生大的畸变;相较H2在纯Al13团簇表面的解离吸附,H2在掺杂团簇Al12X(X=Ni、Cu)表面的解离反应过程中反应能均增大、势垒均降低,这表明掺杂团簇Al12X(X=Ni、Cu)相较纯Al13团簇更有利于H2解离吸附的发生。     

密度泛函理论研究混合团簇Al12X(X=Sc、Ti、V、Gr、Mn、Fe、Co、Ni、Cu、Zn)的结构和磁性

以四种13原子高对称性（Ih、Oh、D5h、D3h）密堆积结构为初始构型,通过不等价位原子替换,利用密度泛函理论系统研究了Al12X(X=Sc、Ti、V、Cr、Mn、Fe、Co、Ni、Cu、Zn）掺杂团簇的结构及磁性．结果表明：除Al12Cr和Al12Fe以外,其它Al12X团簇的基态结构均以Ih替换结构为主,其中前3d元素(X=Sc、Ti、V、Mn)倾向于表面位置替换,而后3d元素(X=Co、Ni、Cu、Zn)则倾向于中心位置替换;Al12Cr和Al12Fe团簇以Oh结构的表面替换为基态结构;对多数3d元素(X=Ti、V、Cr、Fe、Co、Zn)其掺杂团簇均出现明显的近能同分异构现象;相较纯Al13团簇掺杂团簇普遍体现出磁性增强效应．     

混合团簇Cu12A(A=Fe、Co、Ni)结构及能量特性的密度泛函研究

以Cu13非紧致低对称性基态结构及四种13原子高对称性(Ih、Oh、D5h、D3h)密堆积结构为初始构型,通过不等价位原子替换,利用密度泛函理论系统研究了Cu12A (A=Fe、Co、Ni)混合团簇的结构及能量特性.结果表明:Cu12 A(A=Fe、Co)团簇的基态结构均以Ih替换结构为主,且均倾向于中心位置替代的高对称性结构,而Cu12Ni团簇基态则为与Cu13类似的非紧致低对称性结构;Fe、Co、Ni三者对Cu13基态各不等价位替代结构稳定性序列基本相同,而对四种高对称性结构相应中心替代构型稳定性均高于表面替代构型(且Fe、Co均明显强于Ni);对各混合团簇基态结构均无明显同分异构现象.     

连续超短电脉冲对非晶Fe_(78)Si_9B_(13)合金软磁性能的影响

对非晶Fe78Si9B13合金进行了连续超短脉冲电流处理,测量了处理后试样的综合软磁性能.实验证明,当基体金属相αFe(Si)析出量为3%左右,αFe(Si)颗粒大小约为33nm时,可以获得较好的软磁性能.如最大磁导率提高、矫顽力明显降低.利用随机各向异性模型讨论了连续超短脉冲电流处理改善非晶Fe78Si9B13合金软磁性能的机理     

Electronic structure and magnetism of R(Fe,Si)12 (R = Y, Nd)

The newly developed full-potential linearized augmented plane wave (LAPW) and local orbitals (lo) based on standard APW methods are briefly introduced, and the structure and magnetic properties of R(Fe, Si)₁₂ compounds (R = Y, Nd) are calculated using the method. The distribution of Si at different sites is analyzed based on total energy of one crystal unit with structure having been optimized. The characters of magnetic moments, total density of states (TDOS) and partial density of states (PDOS) for different crystal sites Si occupies are obtained and analyzed. The results show that the total magnetic moments of RFe₁₀Si₂ (R = Y, Nd) are larger than those of RFe₁₀ M ₂ (M = Ti, V, Cr, Mn, Mo and W) and the hybridization mechanism is seen as follows. Si(8j) reduce the magnetic moments of Fe at three sites, however, Si(8f) mainly reduce the magnetic moments of Fe(8i) and Fe(8j) atoms. The Curie temperature is markedly enhanced by the introduction of Si atoms according to spin fluctuation of DOS at Fermi level.     

Spin dynamics in (( BEDO-TTF )6[ M (CN)6](H3O,CH3CN)2 ( M = Fe, Cr) crystals

Layered single crystals of the (BEDO-TTF)₆[M(CN)₆](H₃O,CH₃CN)₂ (M = Fe, Cr) compounds with alternating conducting layers of BEDO-TTF and [M(CN)₆](H₃O,CH₃CN)₂ are studied. The contributions to the magnetic susceptibility from charge carriers in BEDO-TTF layers and from the subsystem of localized magnetic moments of iron (or chromium) transition metal complexes are separated for both compounds under investigation. It is revealed that the crystals with [Fe(CN))₆]³⁻ anions at a temperature of ∼80 K and the crystals with [Cr(CN))₆]³⁻ anions at ∼30 K undergo magnetic transitions which are accompanied by drastic changes in the parameters of the EPR lines associated with the BEDO-TTF layers and the subsystem of localized spins of transition metal complexes. It is established that the presence of the BEDO-TTF layers in the structure affects the magnetic properties of iron and chromium hexacyanide complexes. Original Russian Text ? R.B. Morgunov, E.V. Kurganova, T.G. Prokhorova, E.B. Yagubskiĭ, S.V. Simonov, R.P. Shibaeva, 2008, published in Fizika Tverdogo Tela, 2008, Vol. 50, No. 4, pp. 657–663.     

内掺过渡金属非典型富勒烯M@C22(M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni) 几何结构、电子结构、稳定性和磁性的密度泛函研究

采用密度泛函理论中广义梯度近似对非典型富勒烯C₂₂和过渡金属内掺衍生物M@C₂₂(M=Sc,Ti,V,Cr,Mn,Fe,Co和Ni)的几何结构和电子结构进行计算研究.发现非典型富勒烯C₂₂的基态结构是含有一个四碳环的单重态笼状结构.过渡金属原子的掺入明显提高了体系的稳定性. C-M键既有一定共价性又有一定离子性.磁性、能级图、轨道分布和态密度图分析表明: M原子的3d轨道和碳笼的C原子的原子轨道之间存在较强的轨道杂化. Ti, Cr, Fe和Ni内掺的结构出现磁性完全猝灭现象. Sc和碳笼间是弱反铁磁作用, V,Mn和Co与碳笼间是弱铁磁作用.     

Initial oxidation stages on FeCr(100) and FeCr(110) surfaces

Simultaneous LEED and AES are used to follow early stages of oxidation of monocrystalline FeCr(100) and (110) between 700 and 900 K in the oxygen pressure range 10^?9–10^?6 Torr. A chromium-rich oxide region at the alloy/oxide interface is observed, which exhibits different surface structures on oxidized FeCr(100) and FeCr(110). The chromium concentration in this initially formed oxide film is found to be enhanced by low oxygen pressures or high temperatures. During further oxidation different behaviours are observed on FeCr(100) and FeCr(110), which are explained by assuming different ion permeabilities through the initial chromium rich oxide regions on the two surface planes. On FeCr(110) surfaces oxidation is initiated on chromium enriched (100) facets at 800 K or below. At 900 K a film consisting of rhombohedral Cr₂O₃ or (Fe, Cr)₂O₃ is epitaxially growing with its (001) plane parallel to the alloy (110) face. On FeCr(100) surfaces the chromium rich oxide region next to the substrate is of fcc type. As soon as the diffusion of iron from the alloy to the gas/oxide interface is observable, a spinel type oxide is formed and connected with the location of iron in tetrahedral lattice sites. Closer to the fcc lattice the spinel oxide consists of FeCr₂O₄ or a solid solution of FeCr₂O₄ and Fe₃O₄ whereas next to the gas phase the oxide is pure Fe₃O₄.     

非晶态Fe86M4Zr10合金的磁性和电性

本文研究了非晶态Fe₈₆M₄Zr₁₀(M=V,Cr,Mn,Fe,CO,Ni,Cu,B,Si)合金的基本磁性和低温电性,讨论了不同元素M的掺杂对FeZr合金居里温度和磁矩的影响,并用相干交换散射模型解释了样品在居里温度附近出现的电阻率极小。 关键词：     

Electron irradiation effects in doped high temperature superconductors YBa2Cu3? x M x O y (M = Fe, Ni; x=0; x =0:01)

The influence of irradiation by electrons with an energy of 8 MeV, at dose intervals between 10¹³ and 2×10¹⁸el/cm², on the properties of impurity doped, high-temperature superconductor YBa₂Cu_3−x M _x O _y (M = Fe, Ni; x=0; x=0:01) ceramics has been studied. It has been established that, as the irradiation dose is increased, the onset temperature of the transition to the superconducting state (T _c ^on ), and the intergranular weak link coupling temperature between granules (T _m ^J ), exhibit an oscillation around their initial values of approximately about 1–1.5 K. This oscillation indicates that the process of radiation defect formation in HTSC occurs in multiple stages. It was also found that the critical current (J _c )decreases with an increase of the irradiation dose, and exhibits a local minimum at a dose of 8×10¹⁶el/cm²coinciding with minima for T _c ^on and T _m ^J at this dose. It was found that the introduction of Fe atoms to the ceramic decreases T _m ^J , while introducing Ni atoms decreases both T _c ^on and T _m ^J ; it is suggested that this is a result of Ni substitution of Cu both in Cu2 plane sites and Cu1 chain sites. The introduction of Ni causes a large change in the intergranular critical current density, J _c . A critical irradiation dose is obtained (2×10¹⁸)after which all HTSC parameters strongly decrease, i. e. the superconductivity of HTSC is destroyed.      

Inhibition of initial surface oxidation by strongly bound hydroxyl species and Cr segregation: H2O and O2 adsorption on Fe-17Cr

The initial stages of surface oxidation of Fe-17Cr (ferritic stainless steel) were investigated at 323 K by X-ray photoelectron spectroscopy (XPS) and inelastic electron background analysis. The results indicated the formation of a mixed iron-chromium oxide layer upon O₂ exposure and the formation of a thin chromium oxyhydroxide layer upon H₂O exposure. The oxidation of Fe did not occur in the latter case. Moreover, it was found that pre-exposing the Fe-17Cr surface to H₂O significantly hinders subsequent oxidation by O₂, thus providing a way to control the formation of nanoscale oxides on stainless steel materials. It was concluded that the formation of strongly bound hydroxyl species together with adsorbate-induced segregation of Cr severely limits the reaction between O₂/H₂O and Fe from the alloy.     

B对Mo等元素在奥氏体钢/Cr2O3界面占位倾向影响的理论研究

超级奥氏体不锈钢中因含有更高铬、钼含量,具有极高的耐点蚀、晶间腐蚀性能,这与Mo等合金元素对钝化膜结构的影响密切相关,尤其含硼超奥钢钝化层表面Cr、Mo含量明显增加,但其原子层次的微观作用机制尚不清楚.本文采用第一性原理方法,研究了置换原子(Mo、Mn、Ni、Si),及间隙原子B在fcc-Fe/Cr₂O₃界面占位倾向,并分析了可稳定存在于界面B对这些元素偏析倾向的影响.结果表明:Mo、Mn、Ni、Si、B均可与fcc-Fe/Cr₂O₃界面结构体系形成稳定结构;Mo、Ni倾向分布于界面基体侧,Mo有向氧化层扩散的趋势,B处于fcc-Fe/Cr₂O₃界面基体侧更稳定,Mn、Si易分布于氧化层中;存在于界面B对四种元素在fcc-Fe/Cr₂O₃界面体系中的占位影响不同,有利于Mn、Mo偏析于界面基体侧,但抑制Mo向界面基体侧的偏析程度,使得Si、Ni更均匀的分布于基体. Mo等合金元素分布于界面时的态密度来看,界面处M...     

基于β-FeSi2的(Fe, M)Si2三元合金相形成规律

二元β-FeSi₂相是一种重要的窄带半导体型金属硅化物,研究了基于该二元相的三元合金的形成规律,以丰富其材料范围.首先,利用团簇线判据作为理论依据,选取一个团簇和一个连接原子构成的模型,添加不同的第三组元作为连接原子,设计了Fe₃Si₈M(M=B, Cr, Ni, Cu, Co, Al）系列合金成分,即用添加组元替代二元相中的Fe连接原子.然后,用真空吸铸和真空甩带方法制备合金棒以及薄带,以获得无成分偏析的均匀合 关键词： 2')" href="#">β-FeSi₂ 三元合金 团簇线     

铌合金电子结构及其高温氧化行为

为了从电子层面揭示Nb合金高温氧化的物理本质,采用递归法计算了Nb合金的电子态密度、原子镶嵌能、亲和能等电子结构参数,探索Nb合金高温氧化机理.研究表明:氧在Nb中具备较高的扩散速率和溶解度,且氧与Nb较易发生反应,生成氧化物,这使Nb的抗高温氧化性较差.原子镶嵌能的计算结果表明,合金元素Ti,Si,Cr在基体中稳定性较低,易向Nb合金表面扩散,形成富Ti,Si,Cr的表层.合金表层中氧与Nb,Ti,Si,Cr间具有较大亲和性,可以生成相应的氧化物,形成对合金具有保护作用的氧化膜. 关键词： 递归法 高温氧化 Nb合金