Ni-B非晶态合金中电子转移问题的DFT研究

根据Ni-B非晶态结构的短程有序、Ni和B之间是较强的化学作用和结构中存在B-B直接相连的实验事实,选择了Ni~mB~2^(^1^)(m=1-4)原子簇模型,用DFT方法对其进行高水平的量子化学计算,结果表明,模型体系中,B原子供给Ni原子电子,这与非晶态合金的实验结果一致,为了此较,同时选择了NiB^(^2^)(m=1-4)模型,计算结果与实验不符,这说明NiB~2^(^1^)(m=1-4)原子簇模型更能反映非晶态的结构特点。     

类金属P对原子簇Ni_nB_2(n=1～6)性质影响的理论研究

依据实验事实设计组成可调的系列原子簇 NinBP、NinB2 (n = 1～6)模型, 利用密度泛函(DFT)方法在 B3LYP/Lanl2dz 水平上对所设计构型进行优化,得到各原子簇的最稳定构型,进而研究类金属元素 P 对非晶态合金 Ni-B 性质的影响。结果表明:三元非晶态合金 Ni–B–P 的稳定性强于二元非晶态合金 Ni-B;类金属 P 起到调节金属 Ni 原子 3d 轨道布居数的作用。这些均与实验结果一致,说明模型能反映合金的性质。     

Ni-P非晶态合金中电子转移问题的DFT研究

根据Ni-P非晶态合金结构的短程有序、Ni和P之间具较强化学作用和结构中不存在P-P直接相连的实验事实,选择了Ni~nP(n=1-6)原子簇模型,用密度泛函理论方法对其进行计算。结果表明,在模型体系中,随着P含量的减少,电子转移方向发生变化,P原子由得电子变为失电子。这与Ni-P非晶态合金的实验结果一致,说明Ni~nP(n=1-6)原子簇模型能反映Ni-P非晶态合金的结构特点。     

EXAFS研究Ni-B和Ni-Ce-B超细非晶态合金的退火晶化

采用同步辐射EXAFS技术定量地研究化学还原法制备的Ni-B和Ni-Ce-B超细非晶态合金中Ni原子的局域环境结构随退火温度升高而产生的变化,结果表明,对于Ni-B和Ni-Ce-B超细非晶态合金初始样品：Ni-Ni最邻近配位壳层的平均键长RNi-Ni、配位数N、热无序σT、结构无序σs分别为0．275nm,11.9.0.0069nm,0.034nm;0.276nm,12.4,0.0067nm,0.035nm,Ni-B最邻近配位壳层的RNi-B,N, σT,σs分别为0．215nm,2.7,0.0055nm,0.0048nm;0.214nm,2.0,0.0058nm,0.0042nm,Ni-Ni配位的σs很大,是其σT的4－5倍,比Ni－B配位的σs大近一个数量级,在300℃退火后,Ni－B样品开始发生晶化生成晶态Ni3B,其RNi-Ni和σs分别为0．254nm和0．011nm,σs降低近2倍;而．3％原子比的Ce掺入后使Ni-Ce-B超细非晶态合金的晶化温度升高100℃左右。在500℃退火后,Ni－B样品的结构参数与Ni箔的相近,但Ni-Ce-B样品中的Ni-Ni配位的σs仍为0．0073nm,Ni-B配位的N为1．2,表明稀土元素Ce（以CeO2)显著增强了Ni与B的相互作用,且同时使退火晶化成的Ni晶结构产生畸变。     

Co-B非晶态合金中电子转移问题的量子化学研究

根据Co-B非晶态结构的短程有序、Co和B之间是较强的化学作用以及化学键理论,设计了ComB2 (m=1～4) 原子簇模型,用DFT方法对其进行高水平的量子化学计算,结果表明,模型体系ComB2 (m=1～4)中, B原子供给Co原子电子,这与非晶态合金的实验结果一致,同时存在B-B直接相连,为了比较,也选择了ConB (n=1～4)模型,计算结果与实验不符,说明ComB2(m=1～4)原子簇模型更能反映非晶态的结构特点.     

超细非晶镍合金的化学制备及类金属元素对性质的影响

常温下分别使用KBH4和NaH2PO2在水溶液中还原Ni^2^+制得了Ni65B35和Ni89P11超细非晶合金(UFAAP), 同时使用KBH4和NaH2PO2还原Ni^2^+制得了Ni73P13B14UFAAP. Ni-P的粒径较大, 约为110nm, Ni-B的粒径较小, 约为20nm,Ni-P-B的粒径居其之间, 约为40nm。XPS表明, Ni-P间的相互作用强于Ni-B间的相互作用, Ni-P-B中P的电子状态与Ni-P中的相似。Ni-P-B比Ni-P的比表面积高得多,Ni-P-B比Ni-B和Ni-P具有更好的非晶态稳定性, 在573K热处理, 它的非晶态保持完好。晶化结果也表明Ni-P-B中Ni-P间的相互作用比Ni-B间的强。     

Ni-Mo-B非晶态合金纳米颗粒的抗氧化性能研究

在水溶液体系中用化学还原法制备Ni-B和Ni-Mo-B非晶态合金纳米颗粒.SEM测试表明,样品的颗粒形貌呈球形或类球形,平均粒径约10nm.XPS分析结果表明,Ni-Mo-B非晶态合金中钼元素主要以氧化态形成于合金的表面,并导致合金表面合金化硼原子浓度显著增加,氧化态硼（B3＋）的原子浓度显著减少,氧的原子浓度明显减少,合金化镍的原子浓度显著增加,氧化态镍（Ni3＋）的原子浓度显著减少.因此,Ni-Mo-B合金的抗氧化性能显著高于Ni-B合金.XPS谱图分析还表明,在Ni-B和Ni-Mo-B非晶态合金中,存在Ni和B的合金化物Ni2B,其中B失去部分电子,而Ni则富余电子.Ni2B的氧化产生副产物Ni2O3和B2O3.     

Ni-Co-B非晶态合金的结构和催化活性的理论研究

利用一系列原子簇模型Ni~xCo~3~-~xB~2(x=1～3)对Ni-Co-B非晶态合金的电子结构进行了SCC-DV-Xα计算。结果表明,Ni-B非晶态合金的催化加氢活性可通过Co的引入而得到改进。结合EXAFS和活性试验的结果,得出Ni和Co对非晶态Ni-Co-B合金的结构的稳定性有一种协同作用的结论。     

Ni-Co-B非晶态合金的结构和催化活性的理论研究

利用一系列原子簇模型Ni_xCo_(3-x)B_2(x=1～3)对Ni-Co-B非晶态合金的电子结构进行了SCC-DV-Xa计算.结果表明,Ni-B非晶态合金的催化加氢活性可通过Co的引入而得到改进.结合EXAFS和活性试验的结果,得出Ni和Co对非晶态Ni-Co-B合金的结构的稳定性有一种协同作用的结论.     

Ni-B非晶态合金超细微粒的表面性质

非晶态合金具有短程有序和长程无序的结构特点,其优良的催化性能引人注目.但通常熔体急冷法制备的非晶样品表面积甚小.近年来采用化学还原方法制备使非晶态合金兼具超细微粒的性质,从而为非晶态合金在多相催化过程中的应用展示了诱人的前景.因此,研究非晶态合金超细微粒的表面性质就具有重要意义.Okamoto 等发现在用NaBH_4还原水溶液中Ni~(2+)离子制得的Ni-B 超细微粒表面除存在以合金方式结合的Ni、B 物类外还存在由B 水解产生的硼氧化物类,但未能将微粒表面性质与合金结构进行关联.本文报导不同结构状态下Ni-B 超细微粒表面性质的研究结果.     

Theoretical Study on the Catalytic Activity and Sulfur Resistibility of Amorphous Alloy Ni-B-P

In the present paper,one hundred cluster models NinBP (n=1～6) have been designed and studied by density functional theory (DFT) to get an insight into the local structure,catalytic properties and sulfur resistibility of amorphous alloy Ni-B-P. The configurations in triplet state are found more stable than those in the singlet state. It is found that as the content of Ni in the clusters increases,the value of Fermi level in clusters fluctuated,which shows that the content of Ni can influence the Fermi level to a certain extent. Based on the Fermi level and DOS,we consider the activity of catalyst in hydrogenation reaction is the best in cluster Ni3BP. On the basis of the charge of clusters NinBP (n=1～6),we conclude the amorphous alloy Ni-B-P with high Ni content has better sulfur resistibility and the best hydrogenation activity,strong sulfur resistibility appears in clusters Ni3BP,and the amorphous alloy Ni60B20P20 with similar proportion is expected to prepare in the future.     

Quantum Chemical Study on Geometry and Property of Cluster Ni_4P

1INTRODUCTION Amorphous alloys attractive to scientists have worked in the field of materials and catalysts since they have many excellent physical and chemical pro-perties,such as high magnetic susceptibility,high specific heat,high strength,ductile in compression,low coefficient of friction,high corrosion resistance,super plasticity within the range,ferromagnetism and super conductivity[1~5].Especially,amorphous alloys as catalytic materials have shown either hig-her activity or selectiv…     

Co-P非晶态合金电子性质和局域结构的理论研究

In order to study the electron property and the microlocal structure of Co-P amorphous alloy,a series of single-P（ConP）and two-P（ConP2）cluster models were chosen according to the experiment fact of the possible presence of direct P-P contact and short-range-ordering in the amorphous alloy. ConP and ConP2 cluster models were calculated with the DFT method and calculations showed that P（phosphor）accepted electron from Co（cobalt）in single-P（Co2P（2）,Co3P（1）and Co4P（2））cluster models,which agrees well with the Pauli electronegative rule,and a very strong interaction between Co and P resulted in formation stable clusters Co2P（2）,Co3P（1）and Co4P（2）. However,two-P（ConP2）cluster models and single-P cluster Co5P（1）were unstable,and it was impossible to present direct P-P contact in two-P（ConP2）cluster models. It could be concluded that the clusters Co2P（2）,Co3P（1）and Co4P（2） is more reasonable to represent the local structure of Co-P amorphous alloy.     

原子簇Ni2Fe2P结构稳定性的密度泛函理论研究

利用DFT(密度泛函理论)方法在B3LYP/Lan12dz水平下对原子簇模型Ni₂Fe₂P的二十余种可能构型分别在二、四重态下进行优化计算,分析比较了优化结果的能量、结合能、吉布斯自由能变化和过渡态.结果表明:原子簇Ni₂Fe₂P十种异构体没有虚频,有可能稳定存在于非晶态合金中;其中以具有二重态的构型1的能量最低,结合能、吉布斯自由能变化及过渡态能垒最大,最为稳定;四重态中异构体1',2',3'和4'共存的可能性比较大.     

Adsorption of Co2B2 and Ni2B2 Clusters on the TiO2 (110) Surface: a Density Functional Study

Based on density functional theory and generalized gradient approximation calculations, the adsorption of Co2B2 and Ni2B2 clusters on the rutile TiO2 (110) surface has been investigated utilizing periodic supercell models. Unambiguously, the results demonstrate that the hollow site turns out to be preferable for Co2B2 cluster while Ti2 site is for Ni2B2 cluster to adsorb. Orbital population analysis indicates a strong interaction between Co2B2 and O atom of TiO2 surface, which can be attributed to the overlap of Co 3d and surface O 2p orbital. Similarly, for Ni2B2 , the bonding interaction occurs mostly through the interaction of Ni 3d/4s and O 2p orbitals. Note that, there is also an interaction within the Co2B2 clusters (Ni2B2) through B 2s/2p and Co 3d orbitals (Ni 3d/4s). Moreover, orbital analysis results shows that the strong bonding between Ni2B2 and Ti2 site is due to the overlap of HOMO of Ni2B2 and d-orbital of five-coordinated titanium atoms.     

液体和非晶态Ni64B36合金结构的从头算分子动力学模拟

运用从头算分子动力学模拟了液体以及猝冷后形成的非晶态Ni₆₄B₃₆合金体系, 得到了它们的对相关函数、结构因子、键对分析方面的结构信息, 与实验结果相当一致; 结果表明, 猝冷得到的合金性质与液体合金性质相似, 为非晶态结构. B原子多数以B—B双原子成键形式分散于Ni原子构成的骨架中. 电子态密度分析表明, Ni 3d电子最活泼, 因此在合金中Ni为活性位. 轨道电荷分析从电子结构角度揭示了在NiB 催化剂中B作为修饰剂的机理.