液氦冲击压缩特性的理论计算

 用量子力学修正的WCA液体变分微扰理论计算了液氦冲击压缩曲线，计算中体系分子间相互作用势选择EXP-6有效两体势模型，两体势参数通过对实验数据的拟和优选。计算结果在一次冲击压力范围内，冲击温度及压力与Nellis等人的实验数据符合很好，二次冲击数据与实验值稍有偏差，但也在其误差范围内，由于二次冲击只有一个实验点，因此实验数据不能提供更多的信息以供比较。计算结果表明与其他分子间相互作用势相比，选择α值为12.7的EXP-6势更为准确地反映了液氦分子间的相互作用。     

液氩冲击压缩特性的理论计算

用修正的WCA状态方程和Ross变分微扰理论计算了液氩冲击压缩曲线,计算中体系分子间相互作用势选择EXP-6有效两体势模型,计算结果与Nellis等人的实验数据符合较好.     

高温高密度氩物态方程研究

用Exp-6有效两体势模型和液体变分微扰理论计算了液Ar冲击压缩曲线,在35 GPa以下的压力范围内计算的冲击压缩曲线与Thiel 及Nellis等人的实验数据进行了比较.液体分子间Exp-6有效两体势参数根据实验数据计算优选出最佳值,计算结果表明得到的优选参数较为准确地描述了液Ar分子间相互作用.由理论结合实验数据可以认为液氩体系在冲击压力36 GPa以下无相变现象.对较高冲击压力下理论计算的冲击曲线和实验结果之间的偏差作了分析,结合不透明度实验的结果,得到当压力超过35 GPa,温度在12 000 K     

液氩冲击压缩特性的理论计算

用修正的WCA状态方程和Ross变分微扰理论计算了液氩冲击压缩曲线，计算中体系分子间相互作用势选择EXP-6有效两体势模型，计算结果与Nellis等人的实验数据符合较好。     

并五苯同质异相体中分子间势能与能带计算

采用Born-Mayer-Haggins对势模型，分析了并五苯分子间势能及其相互作用. 用紧束缚模型计算了两种并五苯同质异相体结构的能带宽度. 计算带宽随温度升高减小8%—14%. 关键词： 并五苯 同质异相体 分子间势能 能带计算     

Murrell-Sorbie势下He-HCl碰撞体系微分散射截面的研究

根据在CCSD(T)/aug-cc-pVQZ理论水平下计算的He-HCl相互作用能数据,作者采用Murrell-Sorbie势函数形式拟合了He原子与HCl分子相互作用的各向异性势,并与其它势模型进行了比较;然后采用公认的精确度较高的CC近似方法计算了He-HCl碰撞体系的微分散射截面,总结了非弹性微分散射截面的变化规律.研究表明:采用拟合的各向异性势计算的微分散射截面与实验结果符合得很好.拟合势不但表达形式简洁,而且较好地描述了He-HCl系统相互作用的各向异性特征;利用碰撞体系分子间势的量子化学从头计算结果,可解决势能参数难以确定的问题.对进一步研究原子与分子相互作用的机制有一定的参考价值.     

高温高压下爆轰产物分子间相互作用的研究

给出了一种由分子流体的冲击Hugoniot实验数据确定原分子之间和离解产物分子、原子相互间作用势参数的方法. 在较低压强下,采用Ross硬球微扰理论软球修正模型确定原分子之间的相互作用势参数;在较高压强下,采用基于统计物理的化学平衡方法来确定分子离解后的分子和原子之间的相互作用势参数. 与传统的由对应状态定律确定势函数参数的方法相比,所得到的势函数参数在很大的压强范围内都能较好地描述冲击实验. 关键词： 高温高压 化学平衡 冲击Hugoniot实验     

Ⅱ-Ⅵ族化合物原子间两体势的第一性原理研究

本文采用基于第一性原理的Hartree-Fork (HF)方法和密度泛函理论(DFT)计算了CdS、CdSe、CdTe、HgTe等Ⅱ-Ⅵ族化合物的两体相互作用势,并与实验数据进行了比较.分析了计算中基组对计算结果的影响,以及各种近似方法的优缺点.采用Lennard-Jones势、Born-Mayer势和Morse势函数分别对势能值进行拟合,结果表明采用Morse势拟合的势能曲线与计算结果符合最好,说明普遍应用于共价分子的Morse势也同样适用于对Ⅱ-Ⅵ族二聚体的两体势描述.     

苯与PtH分子间电子相互作用的理论研究

采用从头算法在B3LYP水平分别对苯和PtH分子单体及其分子复合物体系(苯-PtH)进行了几何结构优化和振动频率计算,得到了3种苯-PtH分子复合物构型,研究了苯与PtH分子间相互作用对Pt-H键振动频率的影响,并得出了苯与PtH分子之间的相互作用能.     

液氦的冲击压缩理论计算及其等效两体作用势的考察

 选择exp-6势为参考势，运用变分液体微扰理论计算了液氦体系的一次冲击和二次冲击Hugoniot曲线，并与Nellis等的冲击压缩实验数据比较，给出了与Nellis等的实验结果较符合的等效两体相互作用势的参数。研究表明，在计算高温高密度条件下液体的冲击压缩特性时，原子间的多体相互作用十分重要，多体作用的结果是软化了两体相互作用势。     

Calculation of thermodynamic properties of dense neon using statistical mechanical perturbation theory

Abstract

Thermodynamic properties of fluid neon were calculated between 73 and 348 K and up to the melting line, using Ross’ variational perturbation theory. Parameter values for the EXP-6 potential were determined from experimental sound velocity data in the range 100–300 K, 0.1–1 GPa. Calculations with this and several pure pair potentials (XC, HFD), with and without more body interactions, were compared with experimental pVT and sound velocity data. The EXP-6 potential describes the experimental data up to 1 GPa with an accuracy of almost the experimental error. An equation of state is presented in the range from 98 to 348 K and from 0.6 to 6 GPa.     

Equation of state and interaction potential of helium under high temperatures and high densities

Based on the thermodynamics statistic method, the improved variational perturbation theory and the modified quantum mechanics correction model have been used to calculate the equation of state of liquid helium at pressure from 0.7 to 108 GPa. The calculation results are in good agreement with the experimental data. The EXP-6 potential (α = 13.1) can more accurately describe the interaction of helium atoms than other potentials in the scheme. Finally, a comparison is shown between our interatomic potentials and other potentials.     

配合物Benzene-I2结构的从头算研究

采用分子轨道从头算方法,对苯用6-311+G**基组,对碘分子用相对论的有效核实势(RECP5s25p5),以及用密度函数方法(B3LYP),计算了配合物 Benzene-I2可能构形(7种)的结构,总能量和振动频率.经过筛选,同属Cs点群的两种结构是Benzene-I2的稳定结构.自然键轨道 (NBO)分析表明,配合物Benzene-I 2主要是由于苯环的π电子和碘分子的最低空轨道(LUMO)σ*轨道之间的相互作用形成的.本文还给出了这两种结构的势能曲线,并且用含四项Morse函数和一项C6R-6 的势能函数进行曲线拟合,给出了相应的拟合参数.     

Calculation of thermodynamic properties of dense fluid neon using statistical-mechanical perturbation theory

The theory and potentials described in the preceding paper are used for the calculation of thermodynamic properties of fluid neon between 73 and 348 K and up to the melting line. A polynomial equation of state for correlating the densities between 73 and 323 K and between 30 MPa and 1 GPa is presented. The calculations have been extended up to 6 GPa and the performance of the EXP-6 effective pair potential and the HFD-C2, HFD-B and XC3 pure pair potentials is compared. The effect of the Axilrod-Teller many-body correction term on the pure pair potentials is studied. In the ranges 98-348 K and 0·6-6 GPa the density data are correlated by a MBWR equation of state, and a polynomial expression is given for the sound velocity in these ranges. The pressure and temperature dependences of the specific heat at constant volume are shown. A comparison is made between the experimental pVT and soundvelocity data of Kimura et al. at 295 K and up to 3·5 GPa and our calculations.     

Meerwein酯与苯相互作用的1H NMR研究

测定了Meerwein酯(1,3,5,7,-四羧甲基二环[3,3,1]壬-2,6-二烯-2,6-二醇)在四氯化碳和苯混合溶剂中随苯的摩尔分数变化的¹H NMR谱.观察到分子中两类不同的甲基的化学位移随苯的摩尔分数增加都逐渐移向高场,分子中不同位置上的甲基的化学位移向高场移动程度不同,原处低场的甲基的δ比原处高场甲基的δ要大,两条吸收峰在苯的摩尔数渐增时先是重合后又渐渐分开,所有化学位移可以用线性方程δ=A+BX表示.     

First-principles study of benzene on noble metal surfaces: Adsorption states and vacuum level shifts

We have studied the interaction of benzene with Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces using density functional theory (DFT) within a generalized gradient approximation (GGA) and the van der Waals density functional [vdW-DF; M. Dion, H. Rydberg, E. Schröder, D.C. Langreth, B.I. Lundqvist, Phys. Rev. Lett. 92 (2004) 246401]. The adsorption energies using vdW-DF are significantly more accurate than those using GGA, while the equilibrium adsorption distances between benzene and metal substrates () calculated by both GGA and vdW-DF are almost identical. The work function changes induced by the adsorption of benzene are significantly underestimated compared with the experimental values, as a result of the overestimation of by both GGA and vdW-DF. Instead of determining the values from first-principles calculations, we deduced the most probable adsorption distances in such a way as to reproduce the experimentally-observed work function changes. The deduced adsorption distance () is shortest on Cu(1 1 1) while it is longest on Ag(1 1 1), reflecting the strength of the interactions between benzene and the metal surfaces. It turns out that the substrate dependence of the work function change is mainly ascribed to the difference in the benzene–metal distance (Z_C). Charge transfer and work function changes by the adsorption of benzene were analyzed by means of the induced density of interface states (IDIS) model [H. Vázquez, R. Qszwaldowski, P. Pou, J. Ortega, R. Pérez, F. Flores, A. Kahn, Europhys. Lett. 65 (2004) 802], and compared with the self-consistent GGA calculations. The vacuum level shifts estimated by the IDIS model agree with the GGA results for . On the other hand, the discrepancy between the two methods becomes larger for , where the back donation from the metal substrates to the adsorbate becomes significant. We show that the IDIS model reasonably works well for benzene on Cu(1 1 1), Ag(1 1 1) and Au(1 1 1) surfaces because on all surfaces. However, our analysis reveals that the actual charge density redistribution induced by the adsorption of benzene is more complicated than that assumed in the IDIS model.     

Analytical Potential Energy Function for Doubly Charged Ions O2+2, Be2+2 and He2+2

A new analytical potential function is proposed in our preceding paper as which can be used to describe the potential curves for doubly charged diatomic ions with both potential minimum and maximum where ρ=R-Rmin, if R=Rmin, ρ=0, if R=Rmax, ρ=Rmax-Rmin. The parameters a1～a4 are obtained by a least-squares fit based on the ab initio calculations, the values of parameters Rmin and Rmax are fixed from the same calculations. The application of this function is quite flexibly, for it can be also used to describe the potential curves without any potential minimum and maximum, i.e., no stationary point, where ρ=R. The present paper is to examine the proposed potential function form further by describing potential curves of O2+2, Be2+2 and He2+2. The calculations using the theoretical method CID with basis set 6-311++G* have showed the Rmin() and Rmax() to be 1.045 and 1.60, 2.141 and 3.50, and 0.736 and 1.05 for the ground state X1Σ+g of O2+2, Be2+2 and He2+2, respectively, which are in good agreement with reference data. The analytical potential function for the ground state of these doubly charged diatomic ions have been successfully derived for the first time     

二维红外相关光谱在鉴别不同配方树脂中的应用

采用红外光谱结合二维相关分析技术,对添加不同固化促进剂的环氧树脂进行了快速鉴别研究.结果表明,二者在一维红外光谱图上没有差别,但是在二维红外相关谱图上却存在明显的差异.在对4000-2500cm-1和1600-730cm-1两个区域的同步和异步光谱进行研究后发现,配方B有甲基自动峰的出现,而配方A则无;配方A中基团变化顺序为：-CH3＞-CH2＞苯环C=C,醚C-O-C＞一CH2＞苯环C=C,环氧C-O-C＞苯环C=C,苯环=CH＞苯环C=C,苯环=CH＞叔丁基C-C;配方B中基团变化顺序为：环氧C-O-C＞苯环C=C,醚C-O-C＞苯环C=C＞叔丁基C-C,-CH3＞苯环C=C＞叔丁基C-C.研究得到两种树脂体系中-OH、苯环C=C、-CH2、-CH3、叔丁基C-C、醚C-O-C、环氧C-O-C、苯环=CH等基团光谱强度的变化相关性.因此,二维相关红外光谱可以用于揭示树脂反应过程中的高分子链段内不同基团的变化规律和相互作用,并用于一维红外谱图无差别的树脂的鉴别.     

Nuclear quantum effects in calculated NMR shieldings of benzene; a Feynman path integral study

The Feynman path integral Monte Carlo approach has been coupled to the gauge including atomic orbital formalism in order to analyse the absolute magnetic shieldings of the benzene nuclei under the conditions of thermal equilibrium. The Hamiltonian employed in the derivation of ensemble averaged NMR quantities is of the Hartree-Fock type. The basis set used is of 6–31G quality. The spatial delocalization of the atoms leads to a deshielding of both types of benzene nuclei relative to the shieldings experienced at the minimum of the potential energy surface. This deshielding has to be traced back to bond length elongations in thermal equilibrium. The influence of the nuclear fluctuations on the NMR parameters of benzene is quantum driven up to temperatures of 400 K; classical fluctuations are of minor importance in this low-temperature window.