耐蚀合金Al3Ni和Ni3Al液态冷凝过程的比较研究

采用F-S多体势对液态合金Al3Ni和Ni3Al在不同冷却速度下的微观结构及其转变机制进行了分子动力学模拟,得到了不同冷速下各温度的双体分布函数;采用HA键型指数法对其结构进行了分析,结果表明: Al3Ni在两种冷速下均以非晶的形式出现,只是慢冷时体系的有序度略有升高;而Ni3Al的结构及能量转变受冷速影响较大,快冷时形成非晶,而慢冷时出现明显结晶;同样冷速下Al含量较少的Ni3Al体系的有序度高,更易形成晶体,晶体的形成过程中有能量突变.     

原子尺寸差异与非晶形成能力

采用分子动力学模拟技术，研究了纯Au及AuCu合金的熔化、非晶化和晶化过程.模拟结果表明,在冷却速率为5×1011 K•s－1至4×1012 K•s－1的范围内，液态Au总是形成晶体，且冷速越快，结晶温度越低；而AuCu合金则形成非晶，且冷速越快，非晶转变温度越高.验证了原子尺寸的不匹配有利于非晶形成这一规律.     

Al纳米线凝固过程的分子动力学模拟

结合EAM镶嵌原子作用势, 通过经典的分子动力学模拟研究了不同冷却速率下Al纳米线的凝固行为, 并采用键对分析技术探讨了体系中的原子团簇在不同冷却速率下的转化情况. 结果表明, 随着冷却速率的降低, Al纳米线的微观结构从非晶态过渡到多壳螺旋结构, 而多壳螺旋结构具有部分非晶结构的特征, 但是比非晶结构更稳定. 此外, 在冷却速率降低到1×10⁹ K·s-1的情况下, Al纳米线仍然保持多壳螺旋结构.     

二元合金Ag_(50)Rh_(50)从液态到非晶的分子动力学计算

本文对贵重金属银铑合金Ag50Rh50的液态结构和激冷过程进行了分子动力学模拟研究原子间作用势采用紧束缚势模拟在施加了周期性边界条件的常压状态下进行。采用了偶关联函数、键对分析技术和键取向序参数以分子动力学模拟计算方法揭示了Ag50Rh50的液态结构存在原子偏聚特征以及在快速凝固过程形成原子偏聚的不均匀非晶并与同族过渡金属进行了非晶形成能力的比较。     

Cu-Ni合金结构的分子动力学模拟

采用EAM作用势对Cu-Ni合金的结构特性进行了MD模拟研究.通过FZ结构因子可发现,Cu含量的变化对结构因子的波动影响很小,键取向序参数和键对也表现出相似的变化规律,这表明液态Cu-Ni合金对成份变化不敏感,体系中的化学序较弱.将Cu70Ni30合金熔体的FZ结构因子与Waseda的实验结果进行对比,发现二者吻合得较好,表明EAM势可以很好地描绘Cu-Ni合金的结构特性.在快速冷却过程中,除了Cu20Ni80合金外,其他合金成份的双体分布函数的第二峰都发生了劈裂,标志着体系最终形成了非晶结构,而Cu20Ni80合金的双体分布函数却表现出晶体峰的特征.通过对键取向序参数、键型指数以及铜镍原子的有效扩散系数的分析表明,在快速冷却过程中,Cu20Ni80合金最终形成了hcp晶体结构.     

金属Cu液固转变及晶体生长的分子动力学模拟

采用分子动力学模拟研究了液态Ｃｕ在不同冷却速度下的凝固特点,模拟采用ＥＡＭ作用势,计算了不同温度,不同冷却速度下Ｃｕ的偶相关函数,结果表明ＥＡＭ作用势能很好地描述液态Ｃｕ的结构特征,当冷却速度较快时,液Ｃｕ形成非晶;当冷却速度较慢时,液Ｃｕ形成晶体,分析了不同冷却速度下体系的相变热力学及相变动力学过程,最后采用液固两层构型法,描述了Ｃｕ晶体的生长过程。     

二元合金Ag50Rh50从液态到非晶的分子动力学计算

本文对贵重金属银铑合金Ag50Rh50的液态结构和激冷过程进行了分子动力学模拟研究,原子间作用势采用紧束缚势,模拟在施加了周期性边界折常压状态下进行。采用了偶关联函数,键对分析技术和键取向序参, 分子动力学模拟计算方法揭示了Ag50Rh50的液态结构存在原子偏聚特征以及在快速凝固过程形成原子偏聚的不均匀非晶,并与同族过渡金属进行了非晶形成能力的比较。     

金属间化合物Al~3Fe熔体结构的温度变化特性研究

利用分子动力学模拟技术,详细考察了在快速凝固条件下AL~3Fe熔体结构的温度变化特征。结果表明:Al~3Fe熔体中存在不同类型的原子基团.原子集团是以各种各样的键对和多面体的形式存在的.利用键对分析技术,计算出了不同温度下的键对类型数和二十面体的两类键取向序参数,分析了Al-Fe合金在快速凝固条件下非晶形成的演化特点。     

金属Cu熔化结晶过程的分子动力学模拟

采用常温、常压分子动力学模拟技术,研究了在周期性边界条件下,由864个Cu原子构成的模型系统的熔化、结晶过程。原子间相互作用势采用EAM势。模拟结果表明：在连续升温过程中,金属Cu在1520 K熔化;以不同的冷速进行冷却,在较慢冷却条件下,液态Cu在1010 K结晶;当冷速较快时,液态Cu形成非晶态。分析了升降温过程中熔体偶分布函数、原子体积、能量、MSD随温度的变化特征。     

铁磁性物质Co的液态结构分子动力学模拟

用分子动力学模拟方法在１８７３－３００Ｋ的温度范围内对液态Ｃｏ的微正则系综进行了模拟研究,模拟采用ＥＡＭ相互作用势,对时间和空间的平均,得到了不同温度下Ｃｏ的双体分布函数及原子组态变化的重要信息,当冷却速度较慢时,液态金属Ｃｏ最终形成晶态,当冷却速度较快时,液态Ｃｏ最后形成了非晶态,双体分布函数随的变化规律说明液态金属随温度的降低,有序度不断增强,利用键对分析技术对模拟结果作了深入分析,液态金属中     

耐蚀合金Au3 Cu高温冷却过程中能量及结构转变的分子动力学模拟

用分子动力学模拟方法对液态Au3Cu冷却过程进行了研究,考察了不同冷却速度下Au3Cu结构变化特点,原子间相互作用势采用F-S多体势,结构分析采用键取向序和对分析技术.计算结果表明,冷却速度对液态Au3Cu能量及结构转变有重要影响,给出了不同冷却速度下液态Au3Cu结构转变的微观信息.     

Vibrationally averaged isotropic dispersion energy coefficients of the parahydrogen dimer

We compare the sum-over-states and coupled cluster linear response formalisms for the determination of imaginary-frequency polarizabilities of H(2). Using both approaches, we compute isotropic dispersion energy coefficients C(n) (n = 6, 8, 10) for H(2)-H(2) molecular pairs over a wide range of H(2) bond lengths. We present vibrationally averaged dispersion energy coefficients for H(2)-H(2), H(2)-D(2), and D(2)-D(2) molecular pairs and examine the coefficients' convergence with respect to basis set.     

热镀铜层冷凝过程的分子动力学模拟

During the hot-dip process of Cu on the surface of the steel,it involves the solidification from liquid to coating. The cooling rate has great influence on the microstructure and the performance. By means of constanttemperature,constant-pressure molecular dynamics simulation technique,the solidification process of the liquid model system made of 500 Cu particles has been studied with the period boundary condition. With the pairs analysis technology and the bond orientational order method,the difference of the structure and energy of the liquid Cu model system between different cooling velocities has been compared. The significant information of microcosmic structural transformation in the solidification process of liquid Cu system has been obtained. The calculation results show that the Finnis-Sinclair（FS）potential works very well in the solidification process of Cu. Cooling slowly the crystal copper layer can be obtained. Cooling quickly the amorphous copper layer can be obtained.     

A DFT study of the generation of interstellar species XN (X = Cl, and Br) activated by molecular sieve clusters

A cluster DFT (B3LYP) calculation study of ClN₃ and BrN₃ dissociation pathways catalyzed by molecular sieve is reported. A three-tetrahedral molecular sieve cluster (Al(OHSiH₃)(OSiH₃)(OH)₂, called T3) has been chosen in this study. Triplet-state products ClN and BrN are more easily produced with T3 molecular sieve cluster. Although the potential energy surfaces with T3 molecular sieve cluster are similar with those without T3 molecular sieve cluster, the dissociation process of ClN₃ and BrN₃ with T3 molecular sieve cluster becomes easier, which can be attributed to smaller energy gaps from the ground state reactant to the intersystem crossing point.     

The role of dimers in evaporation of small argon clusters

Evaporation of small Lennard-Jones argon clusters has been studied using molecular dynamic simulations. An extensive library of clusters with 4, 5, 6, 11, and 21 atoms has been obtained from an earlier study. Analysis of the evaporation properties of the clusters indicate, that the fraction of dimer evaporations of all evaporation events increases with the total energy of the cluster. The fraction of evaporated dimers from clusters with a constant lifetime is independent of the cluster size for short-lived clusters and increases with cluster size for long-lived clusters. Only a few percent of the clusters which are long lived enough to participate in vapor-liquid nucleation decay by emitting dimers. The mean cluster lifetime as a function of total energy shows the same exponentially decreasing trend for monomer and dimer evaporation channels. The fraction of trimer evaporations is found to be vanishingly small.     

熔体快速冷凝过程的微观结构演化

采用分子动力学模拟技术研究了金属间化合物AuCu3熔体的双体分布函数、键对、多面体、配位数等在快速凝固条件下随温度的变化情况，详细考察了AuCu3中微观组团随温度的演化特点.结果表明，AuCu3熔体降温至700 K时双体分布函数的第二峰已发生劈裂，液态金属中已经产生了非晶态；同时液体中的键对数及多面体数与温度的关系都表明，在上述向非晶转变的过程中，AuCu3熔体的确发生了微观结构组态的变化，其中以液体中的缺陷多面体随温度变化最为剧烈.     

Distribution of distances in donor-acceptor pairs of cyanine dyes upon electronic excitation energy transfer in the presence of DNA

Electronic excitation energy transfer (EEET) between molecules of carbocyanine dyes, which form noncovalent complexes with DNA, has been studied by picosecond spectroscopy. Three oxacarbocyanine dyes have been used as electronic excitation energy donors, and 3,3′-diethylthiacarbocyanine iodide has served as an acceptor dye. An analysis of the kinetic dependences permitted obtaining the data on distribution of the distances in donor-acceptor pairs upon EEET. The effect of the acceptor concentration on the parameters of distribution of its molecules in the quenching microphase has been revealed.