CH_4和CD_4解离吸附的量子含时动力学研究

运用含时波包法 (time -dependentwavepacketmethod) ,对CH4和CD4在光滑静止的Ni( 10 0 )表面的解离吸附进行了量子动力学研究与计算。不同振动态下解离几率随平动能的变化曲线表明 ,反应分子的振动能对分子的解离有重要贡献 ,其反应趋势 ,与其它理论模型得到的结果一致。CH4与CD4解离几率的对数随平动能的变化曲线表明 ,CH4的解离几率比CD4的要高得多 ,这种同位素效应 ,是由它们不同的零点能和量子隧道效应引起的 ,且与实验结果符合得比较好     

CH4和CD4解离吸附的量子含时动力学研究

运用含时波包法(time-dependent wave packet method),对CH4和CD4在光滑静止的Ni(100)表面的解离吸附进行了量子动力学研究与计算.不同振动态下解离几率随平动能的变化曲线表明,反应分子的振动能对分子的解离有重要贡献,其反应趋势,与其它理论模型得到的结果一致.CH4与CD4解离几率的对数随平动能的变化曲线表明,CH4的解离几率比CD4的要高得多,这种同位素效应,是由它们不同的零点能和量子隧道效应引起的,且与实验结果符合得比较好.     

氢及其同位素分子的电子碰撞解离反应截面研究

在边界等离子体中氢及其同位素分子与电子碰撞可以发生解离反应。对于尚无反应截面的氢及其同位素分子电子碰撞激发到三重态然后发生解离反应,作者基于莫尔斯函数、弗兰克－康登原理,采用半经典的Gryzinski方法计算了这一反应截面。得到了解离反应截面的影响因素、反应截面随电子能量的变化情况以及分子的振动能级对反应截面的影响。通过比较表明到排斥态的激发然后发生解离反应的反应截面占据主导地位,比激发到其它三重态激发然后发生解离的反应截面要大一个量级。     

应用SVRT模型对氢与氘代甲烷反应的四维量子散射计算

应用SVRT(Semirigid Vibrating Rotor Target)模型和含时波包法对H CD4→HD CD3反应体系进行了量子散射计算,得出了该体系基态的反应几率,散射截面和热速率常数等量子结果,并比较了靶分子氘代甲烷中氘对氢的替代效应。     

电子与氢及其同位素分子碰撞的非解离性电离截面研究

在边界等离子体中, 氢及其同位素分子与高能电子碰撞可发生电离反应. 对于尚无可利用的氢及其同位素分子的电子碰撞非解离性电离反应截面, 基于莫尔斯函数、弗兰克-康登原理, 采用半经典的Gryzinski方法进行了计算. 得到反应截面随电子能量的变化情况以及振动能级对反应截面的影响. 计算结果表明分子的振动激发对电离反应有着显著影响.     

氢分子3pπ D~1Π_u~ 和4pσ B″1Σ_u~ 态的预解离

运用量子亏损理论，并与参考系变换及本征通道Ｒ矩阵法相结合，建立了描述氢分子里德伯态的预解离过程的理论方法．通过对氢分子的３ｐπＤ１Π＋ｕ和４ｐσＢ″１Σ＋ｕ电子态的预解离过程的研究，阐明其解离的机理，并给出预解离的线宽．     

A12O3X2（X=H，D，T）的电子振动近似方法

用密度泛函理论在B3LYP／6．311＋＋g（d,P）基组水平上对A12O3X2（X=H,D,T）分子的可能较低能量构型进行了几何优化．结果表明该分子的基态电子态和对称性为A12O3X2（X=H,D,T）（1A’）G,计算了氢同位素分子及A12O3X2（X=H,D,T）的电子能量E、定容热容Cv和熵S．用电子振动近似方法计算了固体A12O3的氢化热力学函数△H0,△S0,△G0,以及平衡压力与温度的关系．当A1203吸附氢（氘,氚）形成固体时,反应的氢氘氚排代效应的顺序为氚排代氘,氘排代氢,与钛等金属与氢及其同位素反应的氢氘氚排代效应的顺序相反．总体来说,这种排代效应都非常弱．随着温度的增加,这系列反应的氢氘氚排代效应趋于消失．     

HD~+分子的强场光解离动力学及其量子调控的理论研究

利用精确求解原子核与电子耦合运动的三维含时量子波包法,理论研究了HD~+分子在强激光场中的光解离动力学,并给出了量子调控HD~+分子光解离通道的理论方案.通过分析HD~+分子在不同的初始振动态和激光场强度下的光解离动力学过程及其解离核动能谱,得出了HD~+分子的光解离机理及其随激光场强度的变化规律.研究结果表明,利用激光场的强度可以实现HD~+分子光解离通道的量子调控.当激光场强度I_1=4.0×10~(13) W/cm~2时,HD~+分子的光解离主要是通过净单光子吸收解离和净双光子吸收解离;当激光场强度增大到I_2=2.0×10~(14) W/cm~2时,直接双光子吸收解离取代了净单光子吸收解离,净双光子吸收解离的比重也下降了.     

高压下FCC相金属氢结构稳定性和非谐效应的理论研究

利用第一性原理分子动力学方法研究金属氢体系的非简谐效应, 给出金属氢的声子谱, 讨论金属氢声子谱的温度效应。计算得到氢的同位素氕、氘和氚的FCC相在非零温下的声子谱, 不同温度下的声子谱对比发现零温下3.6 TPa为热力学稳定的临界压强点, 而有限温度下(100 K)临界压强点降到2.8 TPa, 非简谐效应显著地改变了体系的结构稳定性和声子振动性质。     

氢分子3pπ D1πu+和4pσ B″1Σu+态的预解离

运用量子亏损理论，并与参考系变换及本征通道R-矩阵法相结合，建立了描述氢分子里德伯态的预解离过程的理论方法．通过对氢分子的3pπD¹π_u⁺和4pσ B″¹Σ_u⁺电子态的预解离过程的研究，阐明其解离的机理，并给出预解离的线宽． 关键词：     

氘、氦及其混合物状态方程第一原理研究

利用量子分子动力学方法对氘、氦及其混合物的状态方程进行了研究. 计算了氦在密度0.32-5 g/cm³, 温度1000-50000 K范围内的状态方程, 并与化学模型的结果进行了比较; 同时计算了冲击Hugoniot曲线, 与气炮实验的结果符合得很好. 通过计算对分布函数及态密度, 探讨了氦在高温高压下发生金属-绝缘体转变的机理. 计算了氘在密度0.19-0.84 g/cm³, 温度20-50000 K范围内的状态方程; 并计算了理论Hugoniot状态, 由于没有考虑原子的零点运动, 在低温区, 理论结果比实验值小. 对氘氦混合物的状态方程进行了研究, 计算了温度和密度区间为100-50000 K, 0.19-0.84 g/cm³, 不同混合度下的293个状态点的状态方程. 对线性混合近似进行了考查, 结果表明线性混合近似是一个粗略的近似.     

Laser-shock-driven laboratory measurements of the equation of state of hydrogen isotopes in the megabar regime

Abstract

A high intensity laser has been used to shock-compress liquid deuterium to pressures from 0.22 Mbar, near the upper end of gas-gun shock data, to 3.4Mbar. Using a variety of diagnostics, the density, pressure, and reflectivity of the shocked deuterium were determined, culminating in a knowledge of the behavior of hydrogen isotopes along the principal Hugoniot into the Mbar regime. It was found that hydrogen isotopes become highly compressible near 1 Mbar as a result of molecular dissociation and simultaneous ionization. Reflectivity measurements confirmed that deuterium transitions from an insulating state to a conducting phase at pressures near 0.5 Mbar on the Hugoniot and appears to do so in a continuous manner. At pressures above 0.5 Mbar, the measured reflectivity of the shocked deuterium is characteristic of a liquid metal.     

Modeling hot, dense hydrogen with a classical spin dependent hamiltonian

Hot, dense hydrogen is studied with a classical model in which the interaction energy between atoms depends on their internal spins as well as their separation distance. The spins are treated as classical variables. This model is used in Monte Carlo simulations to calculate internal energies, pressures, and pair correlation functions, as well as the Hugoniot for shocked liquid deuterium. The results clearly show the transition of hot, dense hydrogen from a molecular to an atomic fluid. Our results are in reasonable agreement with far more elaborate quantum mechanical simulations.     

稠密氘气物态方程研究

 用二级轻气炮作为加载手段,通过瞬态辐射高温计对样品氘的冲击压缩层的光谱辐射亮度历史进行测量,测得氘气中冲击波速度和冲击温度,并用离解电离平衡方程从理论上分析了冲击压缩下稠密气体的组分,理论计算的Hugoniot曲线及冲击温度和实验结果吻合。     

用多次冲击压缩方法研究稠密氢氦等摩尔混合气体的物态方程

采用液氮冷却以及气体增压技术，制备了～30MPa及～90K初始状态的氢、氦等摩尔混合气体样品.以二级轻气炮作为加载工具，用不同灵敏度设置的两套多通道瞬态高温计系统获得完整、清晰的稠密氢、氦混合气体多次冲击压缩过程的光谱辐射强度信号.并建立起相应的实验数据处理和分析技术，获得了5—140GPa范围内氢、氦混合气体一至五次冲击雨贡纽物态方程，以及一次、二次和四次冲击温度实验数据.流体变分理论和离解模型用来分析和解释所获得的测量结果. 关键词： 氢、氦混合气体 多次冲击压缩 光谱辐射强度历史 物态方程     

A Comparative Study for the Equation of State of Dense Fluid Hydrogen

Recent developments in shock-wave experimental techniques have allowed the 100 GPa range to be probed. Driven by a two-stage gas gun (Livermore, USA) or chemical explosives (Chernogolovka, Russia), the multiple shock-wave technique has been applied to determine the equation of state and the electrical conductivity of dense hydrogen and deuterium fluids. In single shock wave experiments driven by the NOVA laser, the principle Hugoniot curve of deuterium was determined. Interesting effects such as dissociation and the transition to metallic-like conductivities occur under these conditions. The equations of state applied so far to analyze the experimental data are compared and a new semi-empirical equation of state is given.     

Theoretical study of the migration of the hydrogen atom adsorbed on aluminum nanowire

We study the behavior of a hydrogen atom adsorbed on aluminum nanowire based on density functional theory. In this study, we focus on the electronic structure, potential energy surface (PES), and quantum mechanical effects on hydrogen and deuterium atoms. The activation energy of the diffusion of a hydrogen atom to the axis direction is derived as 0.19 eV from PES calculations. The probability density, which is calculated by including quantum effects, is localized on an aluminum top site in both cases of hydrogen and deuterium atoms of the ground state. In addition, some excited states are distributed between aluminum atoms on the surface of the nanowire. The energy difference between the ground state and these excited states are below 0.1 eV, which is much smaller than the activation energy of PES calculations. Thus using these excited states, hydrogen and deuterium atoms may move to the axial direction easily. We also discuss the electronic structure of the nanowire surface using quantum energy density defined by one of the authors.     

Shock compression of deuterium near 100 GPa pressures

The shock-compression curve (Hugoniot) of D2 near 100 GPa pressures (1 Mbar) has been contro-versial because the two published measurements have limiting compressions of fourfold and sixfold. Our purpose is to examine published experimental results to decide which, if either, is probably correct. The published Hugoniot data of low-Z diatomic molecules have a universal behavior. The deuterium data of Knudson et al. (fourfold limiting compression) have this universal behavior, which suggests that Knudson et al. are correct and shows that deuterium behaves as other low-Z elements at high tem-peratures. In D2, H2, N2, CO, and O2, dissociation completes and average kinetic energy dominates average potential energy above approximately 60 GPa. Below approximately 30 GPa, D2, H2, N2, CO, and O2 are diatomic. D2 dissociation is accompanied by a temperature-driven nonmetal-metal transition at approximately 50 GPa.     

高温高密度氢(氘)的物态方程——离解效应研究

 高温高压下流体氢将发生离解化学反应,形成具有相互作用的氢分子和氢原子混合体系,此时粒子间的相互作用复杂。利用单组分流体近似的范德瓦尔斯混合模型,将混合物粒子间的相互作用等效为单组分粒子间相互作用,从而简化了对体系的统计热力学处理;并由自由能函数极小化确定化学平衡时各组分含量、体系的内能、压强。研究了温度在10 000 K以下、密度在0.6 g/cm³以下（相应摩尔体积大于3.3 cm³/mol）区间的热致离解和压致离解现象对流体氢（氘）状态方程的影响。所得结果与双组分流体变分理论计算以及第一原理的分子动力学模拟、蒙特卡罗模拟结果以及二级轻气炮实验数据进行了比较,它们之间的一致性表明：用单组分流体近似的范德瓦尔斯混合模型处理氢（氘）分子的离解区域的物态方程是成功的。     

First principles calculations of shock compressed fluid helium

The properties of hot dense helium at megabar pressures are studied with two first principles computer simulation techniques: path integral Monte Carlo simulation and density functional molecular dynamics. The simulations predict that the compressibility of helium is substantially increased by electronic excitations that are present in the hot fluid at thermodynamic equilibrium. A maximum compression ratio of 5.24(4)-fold the initial density was predicted for 360 GPa and 150,000 K. This result distinguishes helium from deuterium, for which simulations predicted a maximum compression ratio of 4.3(1). Hugoniot curves for statically precompressed samples are also discussed.