NEUTRON SCATTERING AND LATTICE DYNAMICAL STUDIES OF THE HIGH-PRESSURE PHASE ICE (I)

Lattice dynamical calculations of ice VIII have been carried out by using a slightly modified set of force constants obtained recently for ice Ih (Li J C and Ross D K 1993 Nature 365 327). A weak interaction was introduced between the two interpenetrated sublattices in the ice VIII structure. The calculated results for H₂O and D₂O ice VIII are in reasonable agreement with the measured inelastic neutron scattering spectra. The eigenvectors of phonon modes in the range of translational and librational bands have been studied in order to understand the properties of the vibrational modes. It is found that the third peak at 26.7meV in the translation results from weak hydrogen bond interactions, and the first peak (14.7meV) is much higher than it is in ice Ih (～7.1meV), which is partially due to the interactions between the two sublattices.     

Molecular Dynamical Simulation of Water/Ice Phase Transitions within Carbon Nanotubes under Various Pressures

A molecular dynamics simulation is performed for water confined within carbon nanotubes with diameters 11.00 A and 12.38A. Under pressures from 0.1 MPa to 500MPa the simulations are carried out by cooling from 300 K to 240K. Water molecules tend to transform from disordered to ordered with different configurations （square, pentagonal, hexagonal and hexagonal plus a chain）. It is concluded that denser structures may appear under high pressures.     

六氟乙烷分解成氟甲基及其逆反应的A因子和活化能的计算

采用半经典统计方法对过渡态的临界键长进行了具体计算,利用这些结果计算了CF_3+CF_3C_2F_6反应的指数前因子和活化能,计算结果与实验值相当符合。     

Guest-Host Interaction Study in Clathrate Hydrates Using Lattice Dynamics Simulation

Lattice dynamics simulation of several gas hydrates （helium, argon, and methane） with different occupancy rates has been performed using TIP3P potential model. Results show that the coupling between the guest and host is not simple as depicted by the conventional viewpoints. For clathrate hydrate enclosing small guest, the small cages are dominantly responsible for the thermodynamic stability of clathrate hydrates. And the spectrum of methane hydrate is studied compared with argon hydrate, then as a result, shrink effect from positive hydrogen shell is proposed.     

Intrinsic product polarization and branch ratio in the S(~1D,~3P)+HD reaction on three electronic states

The intrinsic product polarization and intramolecular isotope effect of the S(~1D,~3P) + HD reaction have been investigated on both the lowest singlet state(1A) and the triplet state(3A and 3A) potential energy surfaces by using quasi-classical trajectory and quantum mechanical methods.The calculations indicate that intramolecular isotope effects are different on the three electronic states.The stereodynamics study shows that the P(θr) distributions,P(φ r) distributions,and polarization-dependent differential cross sections(PDDCSs)(00) are sensitive to mass factor and the product angular momentum vectors are not only aligned but also oriented.     

Vibration properties of low-fraction hydrogen in deuterium ices

Inelastic incoherent neutron scattering spectra of D2O high-density amorphous （hda） ice, ice-Ⅷ and ice-Ⅱ mixed with small amount of H2O （（5%） have been measured recently on high-energy transfer spectrometer at Rutherford Appleton Laboratory （UK）. The hydrogen atom on D2O ice lattices has three distinguished vibrational modes, two bending at low frequencies and one stretching at high frequencies, and their frequencies are slightly different for different phases of ice. It was found that the lower one of the bending modes is located at -95 meⅤ for hda-ice, at -95 meⅤ for ice-Ⅷ and at -96 meⅤ for ice-Ⅱ and they are all lower than the value of 104 meⅤ for ice-Ih. It was also measured that the O-D and O-H covalent bond stretching modes of ice-Ⅷ are at -315 and -425 meⅤ, ice-Ⅱ at 307 and -415 meⅤ, hda-ice at 312 and -418 meⅤ, respectively. They are significantly higher than the values of ice-Ih at -299 and -406 meⅤ, respectively.     

分子多光子共振吸收的理论研究

首先利用Floquet理论得到共振态的本征函数,再通过求解束缚态与连续态的耦合矩阵而得到束缚态的解离几率,最后得到任一束缚态通过耦合而解离的解离几率及衰变宽度等,利用我们得到的公式,对不转动的双原子分子及双原子分子模型进行了计算,在外场不是特别强的情况下,得到了一些很好的结果。